alloc.c

Go to the documentation of this file.

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * alloc.c
 *
 * Extent allocs and frees
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/quotaops.h>
#include <linux/blkdev.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "blockcheck.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "journal.h"
#include "localalloc.h"
#include "suballoc.h"
#include "sysfile.h"
#include "file.h"
#include "super.h"
#include "uptodate.h"
#include "xattr.h"
#include "refcounttree.h"
#include "ocfs2_trace.h"

#include "buffer_head_io.h"

enum ocfs2_contig_type {
    CONTIG_NONE = 0,
    CONTIG_LEFT,
    CONTIG_RIGHT,
    CONTIG_LEFTRIGHT,
};

static enum ocfs2_contig_type
    ocfs2_extent_rec_contig(struct super_block *sb,
                struct ocfs2_extent_rec *ext,
                struct ocfs2_extent_rec *insert_rec);
/*
 * Operations for a specific extent tree type.
 *
 * To implement an on-disk btree (extent tree) type in ocfs2, add
 * an ocfs2_extent_tree_operations structure and the matching
 * ocfs2_init_<thingy>_extent_tree() function.  That's pretty much it
 * for the allocation portion of the extent tree.
 */
struct ocfs2_extent_tree_operations {
    /*
     * last_eb_blk is the block number of the right most leaf extent
     * block.  Most on-disk structures containing an extent tree store
     * this value for fast access.  The ->eo_set_last_eb_blk() and
     * ->eo_get_last_eb_blk() operations access this value.  They are
     *  both required.
     */
    void (*eo_set_last_eb_blk)(struct ocfs2_extent_tree *et,
                   u64 blkno);
    u64 (*eo_get_last_eb_blk)(struct ocfs2_extent_tree *et);

    /*
     * The on-disk structure usually keeps track of how many total
     * clusters are stored in this extent tree.  This function updates
     * that value.  new_clusters is the delta, and must be
     * added to the total.  Required.
     */
    void (*eo_update_clusters)(struct ocfs2_extent_tree *et,
                   u32 new_clusters);

    /*
     * If this extent tree is supported by an extent map, insert
     * a record into the map.
     */
    void (*eo_extent_map_insert)(struct ocfs2_extent_tree *et,
                     struct ocfs2_extent_rec *rec);

    /*
     * If this extent tree is supported by an extent map, truncate the
     * map to clusters,
     */
    void (*eo_extent_map_truncate)(struct ocfs2_extent_tree *et,
                       u32 clusters);

    /*
     * If ->eo_insert_check() exists, it is called before rec is
     * inserted into the extent tree.  It is optional.
     */
    int (*eo_insert_check)(struct ocfs2_extent_tree *et,
                   struct ocfs2_extent_rec *rec);
    int (*eo_sanity_check)(struct ocfs2_extent_tree *et);

    /*
     * --------------------------------------------------------------
     * The remaining are internal to ocfs2_extent_tree and don't have
     * accessor functions
     */

    /*
     * ->eo_fill_root_el() takes et->et_object and sets et->et_root_el.
     * It is required.
     */
    void (*eo_fill_root_el)(struct ocfs2_extent_tree *et);

    /*
     * ->eo_fill_max_leaf_clusters sets et->et_max_leaf_clusters if
     * it exists.  If it does not, et->et_max_leaf_clusters is set
     * to 0 (unlimited).  Optional.
     */
    void (*eo_fill_max_leaf_clusters)(struct ocfs2_extent_tree *et);

    /*
     * ->eo_extent_contig test whether the 2 ocfs2_extent_rec
     * are contiguous or not. Optional. Don't need to set it if use
     * ocfs2_extent_rec as the tree leaf.
     */
    enum ocfs2_contig_type
        (*eo_extent_contig)(struct ocfs2_extent_tree *et,
                    struct ocfs2_extent_rec *ext,
                    struct ocfs2_extent_rec *insert_rec);
};


/*
 * Pre-declare ocfs2_dinode_et_ops so we can use it as a sanity check
 * in the methods.
 */
static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
                     u64 blkno);
static void ocfs2_dinode_update_clusters(struct ocfs2_extent_tree *et,
                     u32 clusters);
static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                       struct ocfs2_extent_rec *rec);
static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                         u32 clusters);
static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                     struct ocfs2_extent_rec *rec);
static int ocfs2_dinode_sanity_check(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et);
static struct ocfs2_extent_tree_operations ocfs2_dinode_et_ops = {
    .eo_set_last_eb_blk = ocfs2_dinode_set_last_eb_blk,
    .eo_get_last_eb_blk = ocfs2_dinode_get_last_eb_blk,
    .eo_update_clusters = ocfs2_dinode_update_clusters,
    .eo_extent_map_insert   = ocfs2_dinode_extent_map_insert,
    .eo_extent_map_truncate = ocfs2_dinode_extent_map_truncate,
    .eo_insert_check    = ocfs2_dinode_insert_check,
    .eo_sanity_check    = ocfs2_dinode_sanity_check,
    .eo_fill_root_el    = ocfs2_dinode_fill_root_el,
};

static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
                     u64 blkno)
{
    struct ocfs2_dinode *di = et->et_object;

    BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
    di->i_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dinode *di = et->et_object;

    BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
    return le64_to_cpu(di->i_last_eb_blk);
}

static void ocfs2_dinode_update_clusters(struct ocfs2_extent_tree *et,
                     u32 clusters)
{
    struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
    struct ocfs2_dinode *di = et->et_object;

    le32_add_cpu(&di->i_clusters, clusters);
    spin_lock(&oi->ip_lock);
    oi->ip_clusters = le32_to_cpu(di->i_clusters);
    spin_unlock(&oi->ip_lock);
}

static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                       struct ocfs2_extent_rec *rec)
{
    struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

    ocfs2_extent_map_insert_rec(inode, rec);
}

static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                         u32 clusters)
{
    struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

    ocfs2_extent_map_trunc(inode, clusters);
}

static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                     struct ocfs2_extent_rec *rec)
{
    struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
    struct ocfs2_super *osb = OCFS2_SB(oi->vfs_inode.i_sb);

    BUG_ON(oi->ip_dyn_features & OCFS2_INLINE_DATA_FL);
    mlog_bug_on_msg(!ocfs2_sparse_alloc(osb) &&
            (oi->ip_clusters != le32_to_cpu(rec->e_cpos)),
            "Device %s, asking for sparse allocation: inode %llu, "
            "cpos %u, clusters %u\n",
            osb->dev_str,
            (unsigned long long)oi->ip_blkno,
            rec->e_cpos, oi->ip_clusters);

    return 0;
}

static int ocfs2_dinode_sanity_check(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dinode *di = et->et_object;

    BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
    BUG_ON(!OCFS2_IS_VALID_DINODE(di));

    return 0;
}

static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dinode *di = et->et_object;

    et->et_root_el = &di->id2.i_list;
}


static void ocfs2_xattr_value_fill_root_el(struct ocfs2_extent_tree *et)
{
    struct ocfs2_xattr_value_buf *vb = et->et_object;

    et->et_root_el = &vb->vb_xv->xr_list;
}

static void ocfs2_xattr_value_set_last_eb_blk(struct ocfs2_extent_tree *et,
                          u64 blkno)
{
    struct ocfs2_xattr_value_buf *vb = et->et_object;

    vb->vb_xv->xr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_value_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    struct ocfs2_xattr_value_buf *vb = et->et_object;

    return le64_to_cpu(vb->vb_xv->xr_last_eb_blk);
}

static void ocfs2_xattr_value_update_clusters(struct ocfs2_extent_tree *et,
                          u32 clusters)
{
    struct ocfs2_xattr_value_buf *vb = et->et_object;

    le32_add_cpu(&vb->vb_xv->xr_clusters, clusters);
}

static struct ocfs2_extent_tree_operations ocfs2_xattr_value_et_ops = {
    .eo_set_last_eb_blk = ocfs2_xattr_value_set_last_eb_blk,
    .eo_get_last_eb_blk = ocfs2_xattr_value_get_last_eb_blk,
    .eo_update_clusters = ocfs2_xattr_value_update_clusters,
    .eo_fill_root_el    = ocfs2_xattr_value_fill_root_el,
};

static void ocfs2_xattr_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
    struct ocfs2_xattr_block *xb = et->et_object;

    et->et_root_el = &xb->xb_attrs.xb_root.xt_list;
}

static void ocfs2_xattr_tree_fill_max_leaf_clusters(struct ocfs2_extent_tree *et)
{
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
    et->et_max_leaf_clusters =
        ocfs2_clusters_for_bytes(sb, OCFS2_MAX_XATTR_TREE_LEAF_SIZE);
}

static void ocfs2_xattr_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
                         u64 blkno)
{
    struct ocfs2_xattr_block *xb = et->et_object;
    struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

    xt->xt_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    struct ocfs2_xattr_block *xb = et->et_object;
    struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

    return le64_to_cpu(xt->xt_last_eb_blk);
}

static void ocfs2_xattr_tree_update_clusters(struct ocfs2_extent_tree *et,
                         u32 clusters)
{
    struct ocfs2_xattr_block *xb = et->et_object;

    le32_add_cpu(&xb->xb_attrs.xb_root.xt_clusters, clusters);
}

static struct ocfs2_extent_tree_operations ocfs2_xattr_tree_et_ops = {
    .eo_set_last_eb_blk = ocfs2_xattr_tree_set_last_eb_blk,
    .eo_get_last_eb_blk = ocfs2_xattr_tree_get_last_eb_blk,
    .eo_update_clusters = ocfs2_xattr_tree_update_clusters,
    .eo_fill_root_el    = ocfs2_xattr_tree_fill_root_el,
    .eo_fill_max_leaf_clusters = ocfs2_xattr_tree_fill_max_leaf_clusters,
};

static void ocfs2_dx_root_set_last_eb_blk(struct ocfs2_extent_tree *et,
                      u64 blkno)
{
    struct ocfs2_dx_root_block *dx_root = et->et_object;

    dx_root->dr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dx_root_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dx_root_block *dx_root = et->et_object;

    return le64_to_cpu(dx_root->dr_last_eb_blk);
}

static void ocfs2_dx_root_update_clusters(struct ocfs2_extent_tree *et,
                      u32 clusters)
{
    struct ocfs2_dx_root_block *dx_root = et->et_object;

    le32_add_cpu(&dx_root->dr_clusters, clusters);
}

static int ocfs2_dx_root_sanity_check(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dx_root_block *dx_root = et->et_object;

    BUG_ON(!OCFS2_IS_VALID_DX_ROOT(dx_root));

    return 0;
}

static void ocfs2_dx_root_fill_root_el(struct ocfs2_extent_tree *et)
{
    struct ocfs2_dx_root_block *dx_root = et->et_object;

    et->et_root_el = &dx_root->dr_list;
}

static struct ocfs2_extent_tree_operations ocfs2_dx_root_et_ops = {
    .eo_set_last_eb_blk = ocfs2_dx_root_set_last_eb_blk,
    .eo_get_last_eb_blk = ocfs2_dx_root_get_last_eb_blk,
    .eo_update_clusters = ocfs2_dx_root_update_clusters,
    .eo_sanity_check    = ocfs2_dx_root_sanity_check,
    .eo_fill_root_el    = ocfs2_dx_root_fill_root_el,
};

static void ocfs2_refcount_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
    struct ocfs2_refcount_block *rb = et->et_object;

    et->et_root_el = &rb->rf_list;
}

static void ocfs2_refcount_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
                        u64 blkno)
{
    struct ocfs2_refcount_block *rb = et->et_object;

    rb->rf_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_refcount_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    struct ocfs2_refcount_block *rb = et->et_object;

    return le64_to_cpu(rb->rf_last_eb_blk);
}

static void ocfs2_refcount_tree_update_clusters(struct ocfs2_extent_tree *et,
                        u32 clusters)
{
    struct ocfs2_refcount_block *rb = et->et_object;

    le32_add_cpu(&rb->rf_clusters, clusters);
}

static enum ocfs2_contig_type
ocfs2_refcount_tree_extent_contig(struct ocfs2_extent_tree *et,
                  struct ocfs2_extent_rec *ext,
                  struct ocfs2_extent_rec *insert_rec)
{
    return CONTIG_NONE;
}

static struct ocfs2_extent_tree_operations ocfs2_refcount_tree_et_ops = {
    .eo_set_last_eb_blk = ocfs2_refcount_tree_set_last_eb_blk,
    .eo_get_last_eb_blk = ocfs2_refcount_tree_get_last_eb_blk,
    .eo_update_clusters = ocfs2_refcount_tree_update_clusters,
    .eo_fill_root_el    = ocfs2_refcount_tree_fill_root_el,
    .eo_extent_contig   = ocfs2_refcount_tree_extent_contig,
};

static void __ocfs2_init_extent_tree(struct ocfs2_extent_tree *et,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *bh,
                     ocfs2_journal_access_func access,
                     void *obj,
                     struct ocfs2_extent_tree_operations *ops)
{
    et->et_ops = ops;
    et->et_root_bh = bh;
    et->et_ci = ci;
    et->et_root_journal_access = access;
    if (!obj)
        obj = (void *)bh->b_data;
    et->et_object = obj;

    et->et_ops->eo_fill_root_el(et);
    if (!et->et_ops->eo_fill_max_leaf_clusters)
        et->et_max_leaf_clusters = 0;
    else
        et->et_ops->eo_fill_max_leaf_clusters(et);
}

void ocfs2_init_dinode_extent_tree(struct ocfs2_extent_tree *et,
                   struct ocfs2_caching_info *ci,
                   struct buffer_head *bh)
{
    __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_di,
                 NULL, &ocfs2_dinode_et_ops);
}

void ocfs2_init_xattr_tree_extent_tree(struct ocfs2_extent_tree *et,
                       struct ocfs2_caching_info *ci,
                       struct buffer_head *bh)
{
    __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_xb,
                 NULL, &ocfs2_xattr_tree_et_ops);
}

void ocfs2_init_xattr_value_extent_tree(struct ocfs2_extent_tree *et,
                    struct ocfs2_caching_info *ci,
                    struct ocfs2_xattr_value_buf *vb)
{
    __ocfs2_init_extent_tree(et, ci, vb->vb_bh, vb->vb_access, vb,
                 &ocfs2_xattr_value_et_ops);
}

void ocfs2_init_dx_root_extent_tree(struct ocfs2_extent_tree *et,
                    struct ocfs2_caching_info *ci,
                    struct buffer_head *bh)
{
    __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_dr,
                 NULL, &ocfs2_dx_root_et_ops);
}

void ocfs2_init_refcount_extent_tree(struct ocfs2_extent_tree *et,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *bh)
{
    __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_rb,
                 NULL, &ocfs2_refcount_tree_et_ops);
}

static inline void ocfs2_et_set_last_eb_blk(struct ocfs2_extent_tree *et,
                        u64 new_last_eb_blk)
{
    et->et_ops->eo_set_last_eb_blk(et, new_last_eb_blk);
}

static inline u64 ocfs2_et_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
    return et->et_ops->eo_get_last_eb_blk(et);
}

static inline void ocfs2_et_update_clusters(struct ocfs2_extent_tree *et,
                        u32 clusters)
{
    et->et_ops->eo_update_clusters(et, clusters);
}

static inline void ocfs2_et_extent_map_insert(struct ocfs2_extent_tree *et,
                          struct ocfs2_extent_rec *rec)
{
    if (et->et_ops->eo_extent_map_insert)
        et->et_ops->eo_extent_map_insert(et, rec);
}

static inline void ocfs2_et_extent_map_truncate(struct ocfs2_extent_tree *et,
                        u32 clusters)
{
    if (et->et_ops->eo_extent_map_truncate)
        et->et_ops->eo_extent_map_truncate(et, clusters);
}

static inline int ocfs2_et_root_journal_access(handle_t *handle,
                           struct ocfs2_extent_tree *et,
                           int type)
{
    return et->et_root_journal_access(handle, et->et_ci, et->et_root_bh,
                      type);
}

static inline enum ocfs2_contig_type
    ocfs2_et_extent_contig(struct ocfs2_extent_tree *et,
                   struct ocfs2_extent_rec *rec,
                   struct ocfs2_extent_rec *insert_rec)
{
    if (et->et_ops->eo_extent_contig)
        return et->et_ops->eo_extent_contig(et, rec, insert_rec);

    return ocfs2_extent_rec_contig(
                ocfs2_metadata_cache_get_super(et->et_ci),
                rec, insert_rec);
}

static inline int ocfs2_et_insert_check(struct ocfs2_extent_tree *et,
                    struct ocfs2_extent_rec *rec)
{
    int ret = 0;

    if (et->et_ops->eo_insert_check)
        ret = et->et_ops->eo_insert_check(et, rec);
    return ret;
}

static inline int ocfs2_et_sanity_check(struct ocfs2_extent_tree *et)
{
    int ret = 0;

    if (et->et_ops->eo_sanity_check)
        ret = et->et_ops->eo_sanity_check(et);
    return ret;
}

static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
                     struct ocfs2_extent_block *eb);
static void ocfs2_adjust_rightmost_records(handle_t *handle,
                       struct ocfs2_extent_tree *et,
                       struct ocfs2_path *path,
                       struct ocfs2_extent_rec *insert_rec);
/*
 * Reset the actual path elements so that we can re-use the structure
 * to build another path. Generally, this involves freeing the buffer
 * heads.
 */
void ocfs2_reinit_path(struct ocfs2_path *path, int keep_root)
{
    int i, start = 0, depth = 0;
    struct ocfs2_path_item *node;

    if (keep_root)
        start = 1;

    for(i = start; i < path_num_items(path); i++) {
        node = &path->p_node[i];

        brelse(node->bh);
        node->bh = NULL;
        node->el = NULL;
    }

    /*
     * Tree depth may change during truncate, or insert. If we're
     * keeping the root extent list, then make sure that our path
     * structure reflects the proper depth.
     */
    if (keep_root)
        depth = le16_to_cpu(path_root_el(path)->l_tree_depth);
    else
        path_root_access(path) = NULL;

    path->p_tree_depth = depth;
}

void ocfs2_free_path(struct ocfs2_path *path)
{
    if (path) {
        ocfs2_reinit_path(path, 0);
        kfree(path);
    }
}

/*
 * All the elements of src into dest. After this call, src could be freed
 * without affecting dest.
 *
 * Both paths should have the same root. Any non-root elements of dest
 * will be freed.
 */
static void ocfs2_cp_path(struct ocfs2_path *dest, struct ocfs2_path *src)
{
    int i;

    BUG_ON(path_root_bh(dest) != path_root_bh(src));
    BUG_ON(path_root_el(dest) != path_root_el(src));
    BUG_ON(path_root_access(dest) != path_root_access(src));

    ocfs2_reinit_path(dest, 1);

    for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
        dest->p_node[i].bh = src->p_node[i].bh;
        dest->p_node[i].el = src->p_node[i].el;

        if (dest->p_node[i].bh)
            get_bh(dest->p_node[i].bh);
    }
}

/*
 * Make the *dest path the same as src and re-initialize src path to
 * have a root only.
 */
static void ocfs2_mv_path(struct ocfs2_path *dest, struct ocfs2_path *src)
{
    int i;

    BUG_ON(path_root_bh(dest) != path_root_bh(src));
    BUG_ON(path_root_access(dest) != path_root_access(src));

    for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
        brelse(dest->p_node[i].bh);

        dest->p_node[i].bh = src->p_node[i].bh;
        dest->p_node[i].el = src->p_node[i].el;

        src->p_node[i].bh = NULL;
        src->p_node[i].el = NULL;
    }
}

/*
 * Insert an extent block at given index.
 *
 * This will not take an additional reference on eb_bh.
 */
static inline void ocfs2_path_insert_eb(struct ocfs2_path *path, int index,
                    struct buffer_head *eb_bh)
{
    struct ocfs2_extent_block *eb = (struct ocfs2_extent_block *)eb_bh->b_data;

    /*
     * Right now, no root bh is an extent block, so this helps
     * catch code errors with dinode trees. The assertion can be
     * safely removed if we ever need to insert extent block
     * structures at the root.
     */
    BUG_ON(index == 0);

    path->p_node[index].bh = eb_bh;
    path->p_node[index].el = &eb->h_list;
}

static struct ocfs2_path *ocfs2_new_path(struct buffer_head *root_bh,
                     struct ocfs2_extent_list *root_el,
                     ocfs2_journal_access_func access)
{
    struct ocfs2_path *path;

    BUG_ON(le16_to_cpu(root_el->l_tree_depth) >= OCFS2_MAX_PATH_DEPTH);

    path = kzalloc(sizeof(*path), GFP_NOFS);
    if (path) {
        path->p_tree_depth = le16_to_cpu(root_el->l_tree_depth);
        get_bh(root_bh);
        path_root_bh(path) = root_bh;
        path_root_el(path) = root_el;
        path_root_access(path) = access;
    }

    return path;
}

struct ocfs2_path *ocfs2_new_path_from_path(struct ocfs2_path *path)
{
    return ocfs2_new_path(path_root_bh(path), path_root_el(path),
                  path_root_access(path));
}

struct ocfs2_path *ocfs2_new_path_from_et(struct ocfs2_extent_tree *et)
{
    return ocfs2_new_path(et->et_root_bh, et->et_root_el,
                  et->et_root_journal_access);
}

/*
 * Journal the buffer at depth idx.  All idx>0 are extent_blocks,
 * otherwise it's the root_access function.
 *
 * I don't like the way this function's name looks next to
 * ocfs2_journal_access_path(), but I don't have a better one.
 */
int ocfs2_path_bh_journal_access(handle_t *handle,
                 struct ocfs2_caching_info *ci,
                 struct ocfs2_path *path,
                 int idx)
{
    ocfs2_journal_access_func access = path_root_access(path);

    if (!access)
        access = ocfs2_journal_access;

    if (idx)
        access = ocfs2_journal_access_eb;

    return access(handle, ci, path->p_node[idx].bh,
              OCFS2_JOURNAL_ACCESS_WRITE);
}

/*
 * Convenience function to journal all components in a path.
 */
int ocfs2_journal_access_path(struct ocfs2_caching_info *ci,
                  handle_t *handle,
                  struct ocfs2_path *path)
{
    int i, ret = 0;

    if (!path)
        goto out;

    for(i = 0; i < path_num_items(path); i++) {
        ret = ocfs2_path_bh_journal_access(handle, ci, path, i);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

out:
    return ret;
}

/*
 * Return the index of the extent record which contains cluster #v_cluster.
 * -1 is returned if it was not found.
 *
 * Should work fine on interior and exterior nodes.
 */
int ocfs2_search_extent_list(struct ocfs2_extent_list *el, u32 v_cluster)
{
    int ret = -1;
    int i;
    struct ocfs2_extent_rec *rec;
    u32 rec_end, rec_start, clusters;

    for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
        rec = &el->l_recs[i];

        rec_start = le32_to_cpu(rec->e_cpos);
        clusters = ocfs2_rec_clusters(el, rec);

        rec_end = rec_start + clusters;

        if (v_cluster >= rec_start && v_cluster < rec_end) {
            ret = i;
            break;
        }
    }

    return ret;
}

/*
 * NOTE: ocfs2_block_extent_contig(), ocfs2_extents_adjacent() and
 * ocfs2_extent_rec_contig only work properly against leaf nodes!
 */
static int ocfs2_block_extent_contig(struct super_block *sb,
                     struct ocfs2_extent_rec *ext,
                     u64 blkno)
{
    u64 blk_end = le64_to_cpu(ext->e_blkno);

    blk_end += ocfs2_clusters_to_blocks(sb,
                    le16_to_cpu(ext->e_leaf_clusters));

    return blkno == blk_end;
}

static int ocfs2_extents_adjacent(struct ocfs2_extent_rec *left,
                  struct ocfs2_extent_rec *right)
{
    u32 left_range;

    left_range = le32_to_cpu(left->e_cpos) +
        le16_to_cpu(left->e_leaf_clusters);

    return (left_range == le32_to_cpu(right->e_cpos));
}

static enum ocfs2_contig_type
    ocfs2_extent_rec_contig(struct super_block *sb,
                struct ocfs2_extent_rec *ext,
                struct ocfs2_extent_rec *insert_rec)
{
    u64 blkno = le64_to_cpu(insert_rec->e_blkno);

    /*
     * Refuse to coalesce extent records with different flag
     * fields - we don't want to mix unwritten extents with user
     * data.
     */
    if (ext->e_flags != insert_rec->e_flags)
        return CONTIG_NONE;

    if (ocfs2_extents_adjacent(ext, insert_rec) &&
        ocfs2_block_extent_contig(sb, ext, blkno))
            return CONTIG_RIGHT;

    blkno = le64_to_cpu(ext->e_blkno);
    if (ocfs2_extents_adjacent(insert_rec, ext) &&
        ocfs2_block_extent_contig(sb, insert_rec, blkno))
        return CONTIG_LEFT;

    return CONTIG_NONE;
}

/*
 * NOTE: We can have pretty much any combination of contiguousness and
 * appending.
 *
 * The usefulness of APPEND_TAIL is more in that it lets us know that
 * we'll have to update the path to that leaf.
 */
enum ocfs2_append_type {
    APPEND_NONE = 0,
    APPEND_TAIL,
};

enum ocfs2_split_type {
    SPLIT_NONE = 0,
    SPLIT_LEFT,
    SPLIT_RIGHT,
};

struct ocfs2_insert_type {
    enum ocfs2_split_type   ins_split;
    enum ocfs2_append_type  ins_appending;
    enum ocfs2_contig_type  ins_contig;
    int         ins_contig_index;
    int         ins_tree_depth;
};

struct ocfs2_merge_ctxt {
    enum ocfs2_contig_type  c_contig_type;
    int         c_has_empty_extent;
    int         c_split_covers_rec;
};

static int ocfs2_validate_extent_block(struct super_block *sb,
                       struct buffer_head *bh)
{
    int rc;
    struct ocfs2_extent_block *eb =
        (struct ocfs2_extent_block *)bh->b_data;

    trace_ocfs2_validate_extent_block((unsigned long long)bh->b_blocknr);

    BUG_ON(!buffer_uptodate(bh));

    /*
     * If the ecc fails, we return the error but otherwise
     * leave the filesystem running.  We know any error is
     * local to this block.
     */
    rc = ocfs2_validate_meta_ecc(sb, bh->b_data, &eb->h_check);
    if (rc) {
        mlog(ML_ERROR, "Checksum failed for extent block %llu\n",
             (unsigned long long)bh->b_blocknr);
        return rc;
    }

    /*
     * Errors after here are fatal.
     */

    if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
        ocfs2_error(sb,
                "Extent block #%llu has bad signature %.*s",
                (unsigned long long)bh->b_blocknr, 7,
                eb->h_signature);
        return -EINVAL;
    }

    if (le64_to_cpu(eb->h_blkno) != bh->b_blocknr) {
        ocfs2_error(sb,
                "Extent block #%llu has an invalid h_blkno "
                "of %llu",
                (unsigned long long)bh->b_blocknr,
                (unsigned long long)le64_to_cpu(eb->h_blkno));
        return -EINVAL;
    }

    if (le32_to_cpu(eb->h_fs_generation) != OCFS2_SB(sb)->fs_generation) {
        ocfs2_error(sb,
                "Extent block #%llu has an invalid "
                "h_fs_generation of #%u",
                (unsigned long long)bh->b_blocknr,
                le32_to_cpu(eb->h_fs_generation));
        return -EINVAL;
    }

    return 0;
}

int ocfs2_read_extent_block(struct ocfs2_caching_info *ci, u64 eb_blkno,
                struct buffer_head **bh)
{
    int rc;
    struct buffer_head *tmp = *bh;

    rc = ocfs2_read_block(ci, eb_blkno, &tmp,
                  ocfs2_validate_extent_block);

    /* If ocfs2_read_block() got us a new bh, pass it up. */
    if (!rc && !*bh)
        *bh = tmp;

    return rc;
}


/*
 * How many free extents have we got before we need more meta data?
 */
int ocfs2_num_free_extents(struct ocfs2_super *osb,
               struct ocfs2_extent_tree *et)
{
    int retval;
    struct ocfs2_extent_list *el = NULL;
    struct ocfs2_extent_block *eb;
    struct buffer_head *eb_bh = NULL;
    u64 last_eb_blk = 0;

    el = et->et_root_el;
    last_eb_blk = ocfs2_et_get_last_eb_blk(et);

    if (last_eb_blk) {
        retval = ocfs2_read_extent_block(et->et_ci, last_eb_blk,
                         &eb_bh);
        if (retval < 0) {
            mlog_errno(retval);
            goto bail;
        }
        eb = (struct ocfs2_extent_block *) eb_bh->b_data;
        el = &eb->h_list;
    }

    BUG_ON(el->l_tree_depth != 0);

    retval = le16_to_cpu(el->l_count) - le16_to_cpu(el->l_next_free_rec);
bail:
    brelse(eb_bh);

    trace_ocfs2_num_free_extents(retval);
    return retval;
}

/* expects array to already be allocated
 *
 * sets h_signature, h_blkno, h_suballoc_bit, h_suballoc_slot, and
 * l_count for you
 */
static int ocfs2_create_new_meta_bhs(handle_t *handle,
                     struct ocfs2_extent_tree *et,
                     int wanted,
                     struct ocfs2_alloc_context *meta_ac,
                     struct buffer_head *bhs[])
{
    int count, status, i;
    u16 suballoc_bit_start;
    u32 num_got;
    u64 suballoc_loc, first_blkno;
    struct ocfs2_super *osb =
        OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));
    struct ocfs2_extent_block *eb;

    count = 0;
    while (count < wanted) {
        status = ocfs2_claim_metadata(handle,
                          meta_ac,
                          wanted - count,
                          &suballoc_loc,
                          &suballoc_bit_start,
                          &num_got,
                          &first_blkno);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }

        for(i = count;  i < (num_got + count); i++) {
            bhs[i] = sb_getblk(osb->sb, first_blkno);
            if (bhs[i] == NULL) {
                status = -EIO;
                mlog_errno(status);
                goto bail;
            }
            ocfs2_set_new_buffer_uptodate(et->et_ci, bhs[i]);

            status = ocfs2_journal_access_eb(handle, et->et_ci,
                             bhs[i],
                             OCFS2_JOURNAL_ACCESS_CREATE);
            if (status < 0) {
                mlog_errno(status);
                goto bail;
            }

            memset(bhs[i]->b_data, 0, osb->sb->s_blocksize);
            eb = (struct ocfs2_extent_block *) bhs[i]->b_data;
            /* Ok, setup the minimal stuff here. */
            strcpy(eb->h_signature, OCFS2_EXTENT_BLOCK_SIGNATURE);
            eb->h_blkno = cpu_to_le64(first_blkno);
            eb->h_fs_generation = cpu_to_le32(osb->fs_generation);
            eb->h_suballoc_slot =
                cpu_to_le16(meta_ac->ac_alloc_slot);
            eb->h_suballoc_loc = cpu_to_le64(suballoc_loc);
            eb->h_suballoc_bit = cpu_to_le16(suballoc_bit_start);
            eb->h_list.l_count =
                cpu_to_le16(ocfs2_extent_recs_per_eb(osb->sb));

            suballoc_bit_start++;
            first_blkno++;

            /* We'll also be dirtied by the caller, so
             * this isn't absolutely necessary. */
            ocfs2_journal_dirty(handle, bhs[i]);
        }

        count += num_got;
    }

    status = 0;
bail:
    if (status < 0) {
        for(i = 0; i < wanted; i++) {
            brelse(bhs[i]);
            bhs[i] = NULL;
        }
        mlog_errno(status);
    }
    return status;
}

/*
 * Helper function for ocfs2_add_branch() and ocfs2_shift_tree_depth().
 *
 * Returns the sum of the rightmost extent rec logical offset and
 * cluster count.
 *
 * ocfs2_add_branch() uses this to determine what logical cluster
 * value should be populated into the leftmost new branch records.
 *
 * ocfs2_shift_tree_depth() uses this to determine the # clusters
 * value for the new topmost tree record.
 */
static inline u32 ocfs2_sum_rightmost_rec(struct ocfs2_extent_list  *el)
{
    int i;

    i = le16_to_cpu(el->l_next_free_rec) - 1;

    return le32_to_cpu(el->l_recs[i].e_cpos) +
        ocfs2_rec_clusters(el, &el->l_recs[i]);
}

/*
 * Change range of the branches in the right most path according to the leaf
 * extent block's rightmost record.
 */
static int ocfs2_adjust_rightmost_branch(handle_t *handle,
                     struct ocfs2_extent_tree *et)
{
    int status;
    struct ocfs2_path *path = NULL;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec;

    path = ocfs2_new_path_from_et(et);
    if (!path) {
        status = -ENOMEM;
        return status;
    }

    status = ocfs2_find_path(et->et_ci, path, UINT_MAX);
    if (status < 0) {
        mlog_errno(status);
        goto out;
    }

    status = ocfs2_extend_trans(handle, path_num_items(path));
    if (status < 0) {
        mlog_errno(status);
        goto out;
    }

    status = ocfs2_journal_access_path(et->et_ci, handle, path);
    if (status < 0) {
        mlog_errno(status);
        goto out;
    }

    el = path_leaf_el(path);
    rec = &el->l_recs[le16_to_cpu(el->l_next_free_rec) - 1];

    ocfs2_adjust_rightmost_records(handle, et, path, rec);

out:
    ocfs2_free_path(path);
    return status;
}

/*
 * Add an entire tree branch to our inode. eb_bh is the extent block
 * to start at, if we don't want to start the branch at the root
 * structure.
 *
 * last_eb_bh is required as we have to update it's next_leaf pointer
 * for the new last extent block.
 *
 * the new branch will be 'empty' in the sense that every block will
 * contain a single record with cluster count == 0.
 */
static int ocfs2_add_branch(handle_t *handle,
                struct ocfs2_extent_tree *et,
                struct buffer_head *eb_bh,
                struct buffer_head **last_eb_bh,
                struct ocfs2_alloc_context *meta_ac)
{
    int status, new_blocks, i;
    u64 next_blkno, new_last_eb_blk;
    struct buffer_head *bh;
    struct buffer_head **new_eb_bhs = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list  *eb_el;
    struct ocfs2_extent_list  *el;
    u32 new_cpos, root_end;

    BUG_ON(!last_eb_bh || !*last_eb_bh);

    if (eb_bh) {
        eb = (struct ocfs2_extent_block *) eb_bh->b_data;
        el = &eb->h_list;
    } else
        el = et->et_root_el;

    /* we never add a branch to a leaf. */
    BUG_ON(!el->l_tree_depth);

    new_blocks = le16_to_cpu(el->l_tree_depth);

    eb = (struct ocfs2_extent_block *)(*last_eb_bh)->b_data;
    new_cpos = ocfs2_sum_rightmost_rec(&eb->h_list);
    root_end = ocfs2_sum_rightmost_rec(et->et_root_el);

    /*
     * If there is a gap before the root end and the real end
     * of the righmost leaf block, we need to remove the gap
     * between new_cpos and root_end first so that the tree
     * is consistent after we add a new branch(it will start
     * from new_cpos).
     */
    if (root_end > new_cpos) {
        trace_ocfs2_adjust_rightmost_branch(
            (unsigned long long)
            ocfs2_metadata_cache_owner(et->et_ci),
            root_end, new_cpos);

        status = ocfs2_adjust_rightmost_branch(handle, et);
        if (status) {
            mlog_errno(status);
            goto bail;
        }
    }

    /* allocate the number of new eb blocks we need */
    new_eb_bhs = kcalloc(new_blocks, sizeof(struct buffer_head *),
                 GFP_KERNEL);
    if (!new_eb_bhs) {
        status = -ENOMEM;
        mlog_errno(status);
        goto bail;
    }

    status = ocfs2_create_new_meta_bhs(handle, et, new_blocks,
                       meta_ac, new_eb_bhs);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    /* Note: new_eb_bhs[new_blocks - 1] is the guy which will be
     * linked with the rest of the tree.
     * conversly, new_eb_bhs[0] is the new bottommost leaf.
     *
     * when we leave the loop, new_last_eb_blk will point to the
     * newest leaf, and next_blkno will point to the topmost extent
     * block. */
    next_blkno = new_last_eb_blk = 0;
    for(i = 0; i < new_blocks; i++) {
        bh = new_eb_bhs[i];
        eb = (struct ocfs2_extent_block *) bh->b_data;
        /* ocfs2_create_new_meta_bhs() should create it right! */
        BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));
        eb_el = &eb->h_list;

        status = ocfs2_journal_access_eb(handle, et->et_ci, bh,
                         OCFS2_JOURNAL_ACCESS_CREATE);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }

        eb->h_next_leaf_blk = 0;
        eb_el->l_tree_depth = cpu_to_le16(i);
        eb_el->l_next_free_rec = cpu_to_le16(1);
        /*
         * This actually counts as an empty extent as
         * c_clusters == 0
         */
        eb_el->l_recs[0].e_cpos = cpu_to_le32(new_cpos);
        eb_el->l_recs[0].e_blkno = cpu_to_le64(next_blkno);
        /*
         * eb_el isn't always an interior node, but even leaf
         * nodes want a zero'd flags and reserved field so
         * this gets the whole 32 bits regardless of use.
         */
        eb_el->l_recs[0].e_int_clusters = cpu_to_le32(0);
        if (!eb_el->l_tree_depth)
            new_last_eb_blk = le64_to_cpu(eb->h_blkno);

        ocfs2_journal_dirty(handle, bh);
        next_blkno = le64_to_cpu(eb->h_blkno);
    }

    /* This is a bit hairy. We want to update up to three blocks
     * here without leaving any of them in an inconsistent state
     * in case of error. We don't have to worry about
     * journal_dirty erroring as it won't unless we've aborted the
     * handle (in which case we would never be here) so reserving
     * the write with journal_access is all we need to do. */
    status = ocfs2_journal_access_eb(handle, et->et_ci, *last_eb_bh,
                     OCFS2_JOURNAL_ACCESS_WRITE);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }
    status = ocfs2_et_root_journal_access(handle, et,
                          OCFS2_JOURNAL_ACCESS_WRITE);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }
    if (eb_bh) {
        status = ocfs2_journal_access_eb(handle, et->et_ci, eb_bh,
                         OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }
    }

    /* Link the new branch into the rest of the tree (el will
     * either be on the root_bh, or the extent block passed in. */
    i = le16_to_cpu(el->l_next_free_rec);
    el->l_recs[i].e_blkno = cpu_to_le64(next_blkno);
    el->l_recs[i].e_cpos = cpu_to_le32(new_cpos);
    el->l_recs[i].e_int_clusters = 0;
    le16_add_cpu(&el->l_next_free_rec, 1);

    /* fe needs a new last extent block pointer, as does the
     * next_leaf on the previously last-extent-block. */
    ocfs2_et_set_last_eb_blk(et, new_last_eb_blk);

    eb = (struct ocfs2_extent_block *) (*last_eb_bh)->b_data;
    eb->h_next_leaf_blk = cpu_to_le64(new_last_eb_blk);

    ocfs2_journal_dirty(handle, *last_eb_bh);
    ocfs2_journal_dirty(handle, et->et_root_bh);
    if (eb_bh)
        ocfs2_journal_dirty(handle, eb_bh);

    /*
     * Some callers want to track the rightmost leaf so pass it
     * back here.
     */
    brelse(*last_eb_bh);
    get_bh(new_eb_bhs[0]);
    *last_eb_bh = new_eb_bhs[0];

    status = 0;
bail:
    if (new_eb_bhs) {
        for (i = 0; i < new_blocks; i++)
            brelse(new_eb_bhs[i]);
        kfree(new_eb_bhs);
    }

    return status;
}

/*
 * adds another level to the allocation tree.
 * returns back the new extent block so you can add a branch to it
 * after this call.
 */
static int ocfs2_shift_tree_depth(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_alloc_context *meta_ac,
                  struct buffer_head **ret_new_eb_bh)
{
    int status, i;
    u32 new_clusters;
    struct buffer_head *new_eb_bh = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list  *root_el;
    struct ocfs2_extent_list  *eb_el;

    status = ocfs2_create_new_meta_bhs(handle, et, 1, meta_ac,
                       &new_eb_bh);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    eb = (struct ocfs2_extent_block *) new_eb_bh->b_data;
    /* ocfs2_create_new_meta_bhs() should create it right! */
    BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));

    eb_el = &eb->h_list;
    root_el = et->et_root_el;

    status = ocfs2_journal_access_eb(handle, et->et_ci, new_eb_bh,
                     OCFS2_JOURNAL_ACCESS_CREATE);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    /* copy the root extent list data into the new extent block */
    eb_el->l_tree_depth = root_el->l_tree_depth;
    eb_el->l_next_free_rec = root_el->l_next_free_rec;
    for (i = 0; i < le16_to_cpu(root_el->l_next_free_rec); i++)
        eb_el->l_recs[i] = root_el->l_recs[i];

    ocfs2_journal_dirty(handle, new_eb_bh);

    status = ocfs2_et_root_journal_access(handle, et,
                          OCFS2_JOURNAL_ACCESS_WRITE);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    new_clusters = ocfs2_sum_rightmost_rec(eb_el);

    /* update root_bh now */
    le16_add_cpu(&root_el->l_tree_depth, 1);
    root_el->l_recs[0].e_cpos = 0;
    root_el->l_recs[0].e_blkno = eb->h_blkno;
    root_el->l_recs[0].e_int_clusters = cpu_to_le32(new_clusters);
    for (i = 1; i < le16_to_cpu(root_el->l_next_free_rec); i++)
        memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
    root_el->l_next_free_rec = cpu_to_le16(1);

    /* If this is our 1st tree depth shift, then last_eb_blk
     * becomes the allocated extent block */
    if (root_el->l_tree_depth == cpu_to_le16(1))
        ocfs2_et_set_last_eb_blk(et, le64_to_cpu(eb->h_blkno));

    ocfs2_journal_dirty(handle, et->et_root_bh);

    *ret_new_eb_bh = new_eb_bh;
    new_eb_bh = NULL;
    status = 0;
bail:
    brelse(new_eb_bh);

    return status;
}

/*
 * Should only be called when there is no space left in any of the
 * leaf nodes. What we want to do is find the lowest tree depth
 * non-leaf extent block with room for new records. There are three
 * valid results of this search:
 *
 * 1) a lowest extent block is found, then we pass it back in
 *    *lowest_eb_bh and return '0'
 *
 * 2) the search fails to find anything, but the root_el has room. We
 *    pass NULL back in *lowest_eb_bh, but still return '0'
 *
 * 3) the search fails to find anything AND the root_el is full, in
 *    which case we return > 0
 *
 * return status < 0 indicates an error.
 */
static int ocfs2_find_branch_target(struct ocfs2_extent_tree *et,
                    struct buffer_head **target_bh)
{
    int status = 0, i;
    u64 blkno;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list  *el;
    struct buffer_head *bh = NULL;
    struct buffer_head *lowest_bh = NULL;

    *target_bh = NULL;

    el = et->et_root_el;

    while(le16_to_cpu(el->l_tree_depth) > 1) {
        if (le16_to_cpu(el->l_next_free_rec) == 0) {
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu has empty "
                    "extent list (next_free_rec == 0)",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci));
            status = -EIO;
            goto bail;
        }
        i = le16_to_cpu(el->l_next_free_rec) - 1;
        blkno = le64_to_cpu(el->l_recs[i].e_blkno);
        if (!blkno) {
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu has extent "
                    "list where extent # %d has no physical "
                    "block start",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci), i);
            status = -EIO;
            goto bail;
        }

        brelse(bh);
        bh = NULL;

        status = ocfs2_read_extent_block(et->et_ci, blkno, &bh);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }

        eb = (struct ocfs2_extent_block *) bh->b_data;
        el = &eb->h_list;

        if (le16_to_cpu(el->l_next_free_rec) <
            le16_to_cpu(el->l_count)) {
            brelse(lowest_bh);
            lowest_bh = bh;
            get_bh(lowest_bh);
        }
    }

    /* If we didn't find one and the fe doesn't have any room,
     * then return '1' */
    el = et->et_root_el;
    if (!lowest_bh && (el->l_next_free_rec == el->l_count))
        status = 1;

    *target_bh = lowest_bh;
bail:
    brelse(bh);

    return status;
}

/*
 * Grow a b-tree so that it has more records.
 *
 * We might shift the tree depth in which case existing paths should
 * be considered invalid.
 *
 * Tree depth after the grow is returned via *final_depth.
 *
 * *last_eb_bh will be updated by ocfs2_add_branch().
 */
static int ocfs2_grow_tree(handle_t *handle, struct ocfs2_extent_tree *et,
               int *final_depth, struct buffer_head **last_eb_bh,
               struct ocfs2_alloc_context *meta_ac)
{
    int ret, shift;
    struct ocfs2_extent_list *el = et->et_root_el;
    int depth = le16_to_cpu(el->l_tree_depth);
    struct buffer_head *bh = NULL;

    BUG_ON(meta_ac == NULL);

    shift = ocfs2_find_branch_target(et, &bh);
    if (shift < 0) {
        ret = shift;
        mlog_errno(ret);
        goto out;
    }

    /* We traveled all the way to the bottom of the allocation tree
     * and didn't find room for any more extents - we need to add
     * another tree level */
    if (shift) {
        BUG_ON(bh);
        trace_ocfs2_grow_tree(
            (unsigned long long)
            ocfs2_metadata_cache_owner(et->et_ci),
            depth);

        /* ocfs2_shift_tree_depth will return us a buffer with
         * the new extent block (so we can pass that to
         * ocfs2_add_branch). */
        ret = ocfs2_shift_tree_depth(handle, et, meta_ac, &bh);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
        depth++;
        if (depth == 1) {
            /*
             * Special case: we have room now if we shifted from
             * tree_depth 0, so no more work needs to be done.
             *
             * We won't be calling add_branch, so pass
             * back *last_eb_bh as the new leaf. At depth
             * zero, it should always be null so there's
             * no reason to brelse.
             */
            BUG_ON(*last_eb_bh);
            get_bh(bh);
            *last_eb_bh = bh;
            goto out;
        }
    }

    /* call ocfs2_add_branch to add the final part of the tree with
     * the new data. */
    ret = ocfs2_add_branch(handle, et, bh, last_eb_bh,
                   meta_ac);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

out:
    if (final_depth)
        *final_depth = depth;
    brelse(bh);
    return ret;
}

/*
 * This function will discard the rightmost extent record.
 */
static void ocfs2_shift_records_right(struct ocfs2_extent_list *el)
{
    int next_free = le16_to_cpu(el->l_next_free_rec);
    int count = le16_to_cpu(el->l_count);
    unsigned int num_bytes;

    BUG_ON(!next_free);
    /* This will cause us to go off the end of our extent list. */
    BUG_ON(next_free >= count);

    num_bytes = sizeof(struct ocfs2_extent_rec) * next_free;

    memmove(&el->l_recs[1], &el->l_recs[0], num_bytes);
}

static void ocfs2_rotate_leaf(struct ocfs2_extent_list *el,
                  struct ocfs2_extent_rec *insert_rec)
{
    int i, insert_index, next_free, has_empty, num_bytes;
    u32 insert_cpos = le32_to_cpu(insert_rec->e_cpos);
    struct ocfs2_extent_rec *rec;

    next_free = le16_to_cpu(el->l_next_free_rec);
    has_empty = ocfs2_is_empty_extent(&el->l_recs[0]);

    BUG_ON(!next_free);

    /* The tree code before us didn't allow enough room in the leaf. */
    BUG_ON(el->l_next_free_rec == el->l_count && !has_empty);

    /*
     * The easiest way to approach this is to just remove the
     * empty extent and temporarily decrement next_free.
     */
    if (has_empty) {
        /*
         * If next_free was 1 (only an empty extent), this
         * loop won't execute, which is fine. We still want
         * the decrement above to happen.
         */
        for(i = 0; i < (next_free - 1); i++)
            el->l_recs[i] = el->l_recs[i+1];

        next_free--;
    }

    /*
     * Figure out what the new record index should be.
     */
    for(i = 0; i < next_free; i++) {
        rec = &el->l_recs[i];

        if (insert_cpos < le32_to_cpu(rec->e_cpos))
            break;
    }
    insert_index = i;

    trace_ocfs2_rotate_leaf(insert_cpos, insert_index,
                has_empty, next_free,
                le16_to_cpu(el->l_count));

    BUG_ON(insert_index < 0);
    BUG_ON(insert_index >= le16_to_cpu(el->l_count));
    BUG_ON(insert_index > next_free);

    /*
     * No need to memmove if we're just adding to the tail.
     */
    if (insert_index != next_free) {
        BUG_ON(next_free >= le16_to_cpu(el->l_count));

        num_bytes = next_free - insert_index;
        num_bytes *= sizeof(struct ocfs2_extent_rec);
        memmove(&el->l_recs[insert_index + 1],
            &el->l_recs[insert_index],
            num_bytes);
    }

    /*
     * Either we had an empty extent, and need to re-increment or
     * there was no empty extent on a non full rightmost leaf node,
     * in which case we still need to increment.
     */
    next_free++;
    el->l_next_free_rec = cpu_to_le16(next_free);
    /*
     * Make sure none of the math above just messed up our tree.
     */
    BUG_ON(le16_to_cpu(el->l_next_free_rec) > le16_to_cpu(el->l_count));

    el->l_recs[insert_index] = *insert_rec;

}

static void ocfs2_remove_empty_extent(struct ocfs2_extent_list *el)
{
    int size, num_recs = le16_to_cpu(el->l_next_free_rec);

    BUG_ON(num_recs == 0);

    if (ocfs2_is_empty_extent(&el->l_recs[0])) {
        num_recs--;
        size = num_recs * sizeof(struct ocfs2_extent_rec);
        memmove(&el->l_recs[0], &el->l_recs[1], size);
        memset(&el->l_recs[num_recs], 0,
               sizeof(struct ocfs2_extent_rec));
        el->l_next_free_rec = cpu_to_le16(num_recs);
    }
}

/*
 * Create an empty extent record .
 *
 * l_next_free_rec may be updated.
 *
 * If an empty extent already exists do nothing.
 */
static void ocfs2_create_empty_extent(struct ocfs2_extent_list *el)
{
    int next_free = le16_to_cpu(el->l_next_free_rec);

    BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

    if (next_free == 0)
        goto set_and_inc;

    if (ocfs2_is_empty_extent(&el->l_recs[0]))
        return;

    mlog_bug_on_msg(el->l_count == el->l_next_free_rec,
            "Asked to create an empty extent in a full list:\n"
            "count = %u, tree depth = %u",
            le16_to_cpu(el->l_count),
            le16_to_cpu(el->l_tree_depth));

    ocfs2_shift_records_right(el);

set_and_inc:
    le16_add_cpu(&el->l_next_free_rec, 1);
    memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
}

/*
 * For a rotation which involves two leaf nodes, the "root node" is
 * the lowest level tree node which contains a path to both leafs. This
 * resulting set of information can be used to form a complete "subtree"
 *
 * This function is passed two full paths from the dinode down to a
 * pair of adjacent leaves. It's task is to figure out which path
 * index contains the subtree root - this can be the root index itself
 * in a worst-case rotation.
 *
 * The array index of the subtree root is passed back.
 */
int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
                struct ocfs2_path *left,
                struct ocfs2_path *right)
{
    int i = 0;

    /*
     * Check that the caller passed in two paths from the same tree.
     */
    BUG_ON(path_root_bh(left) != path_root_bh(right));

    do {
        i++;

        /*
         * The caller didn't pass two adjacent paths.
         */
        mlog_bug_on_msg(i > left->p_tree_depth,
                "Owner %llu, left depth %u, right depth %u\n"
                "left leaf blk %llu, right leaf blk %llu\n",
                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                left->p_tree_depth, right->p_tree_depth,
                (unsigned long long)path_leaf_bh(left)->b_blocknr,
                (unsigned long long)path_leaf_bh(right)->b_blocknr);
    } while (left->p_node[i].bh->b_blocknr ==
         right->p_node[i].bh->b_blocknr);

    return i - 1;
}

typedef void (path_insert_t)(void *, struct buffer_head *);

/*
 * Traverse a btree path in search of cpos, starting at root_el.
 *
 * This code can be called with a cpos larger than the tree, in which
 * case it will return the rightmost path.
 */
static int __ocfs2_find_path(struct ocfs2_caching_info *ci,
                 struct ocfs2_extent_list *root_el, u32 cpos,
                 path_insert_t *func, void *data)
{
    int i, ret = 0;
    u32 range;
    u64 blkno;
    struct buffer_head *bh = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec;

    el = root_el;
    while (el->l_tree_depth) {
        if (le16_to_cpu(el->l_next_free_rec) == 0) {
            ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                    "Owner %llu has empty extent list at "
                    "depth %u\n",
                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                    le16_to_cpu(el->l_tree_depth));
            ret = -EROFS;
            goto out;

        }

        for(i = 0; i < le16_to_cpu(el->l_next_free_rec) - 1; i++) {
            rec = &el->l_recs[i];

            /*
             * In the case that cpos is off the allocation
             * tree, this should just wind up returning the
             * rightmost record.
             */
            range = le32_to_cpu(rec->e_cpos) +
                ocfs2_rec_clusters(el, rec);
            if (cpos >= le32_to_cpu(rec->e_cpos) && cpos < range)
                break;
        }

        blkno = le64_to_cpu(el->l_recs[i].e_blkno);
        if (blkno == 0) {
            ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                    "Owner %llu has bad blkno in extent list "
                    "at depth %u (index %d)\n",
                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                    le16_to_cpu(el->l_tree_depth), i);
            ret = -EROFS;
            goto out;
        }

        brelse(bh);
        bh = NULL;
        ret = ocfs2_read_extent_block(ci, blkno, &bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        eb = (struct ocfs2_extent_block *) bh->b_data;
        el = &eb->h_list;

        if (le16_to_cpu(el->l_next_free_rec) >
            le16_to_cpu(el->l_count)) {
            ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                    "Owner %llu has bad count in extent list "
                    "at block %llu (next free=%u, count=%u)\n",
                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                    (unsigned long long)bh->b_blocknr,
                    le16_to_cpu(el->l_next_free_rec),
                    le16_to_cpu(el->l_count));
            ret = -EROFS;
            goto out;
        }

        if (func)
            func(data, bh);
    }

out:
    /*
     * Catch any trailing bh that the loop didn't handle.
     */
    brelse(bh);

    return ret;
}

/*
 * Given an initialized path (that is, it has a valid root extent
 * list), this function will traverse the btree in search of the path
 * which would contain cpos.
 *
 * The path traveled is recorded in the path structure.
 *
 * Note that this will not do any comparisons on leaf node extent
 * records, so it will work fine in the case that we just added a tree
 * branch.
 */
struct find_path_data {
    int index;
    struct ocfs2_path *path;
};
static void find_path_ins(void *data, struct buffer_head *bh)
{
    struct find_path_data *fp = data;

    get_bh(bh);
    ocfs2_path_insert_eb(fp->path, fp->index, bh);
    fp->index++;
}
int ocfs2_find_path(struct ocfs2_caching_info *ci,
            struct ocfs2_path *path, u32 cpos)
{
    struct find_path_data data;

    data.index = 1;
    data.path = path;
    return __ocfs2_find_path(ci, path_root_el(path), cpos,
                 find_path_ins, &data);
}

static void find_leaf_ins(void *data, struct buffer_head *bh)
{
    struct ocfs2_extent_block *eb =(struct ocfs2_extent_block *)bh->b_data;
    struct ocfs2_extent_list *el = &eb->h_list;
    struct buffer_head **ret = data;

    /* We want to retain only the leaf block. */
    if (le16_to_cpu(el->l_tree_depth) == 0) {
        get_bh(bh);
        *ret = bh;
    }
}
/*
 * Find the leaf block in the tree which would contain cpos. No
 * checking of the actual leaf is done.
 *
 * Some paths want to call this instead of allocating a path structure
 * and calling ocfs2_find_path().
 *
 * This function doesn't handle non btree extent lists.
 */
int ocfs2_find_leaf(struct ocfs2_caching_info *ci,
            struct ocfs2_extent_list *root_el, u32 cpos,
            struct buffer_head **leaf_bh)
{
    int ret;
    struct buffer_head *bh = NULL;

    ret = __ocfs2_find_path(ci, root_el, cpos, find_leaf_ins, &bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    *leaf_bh = bh;
out:
    return ret;
}

/*
 * Adjust the adjacent records (left_rec, right_rec) involved in a rotation.
 *
 * Basically, we've moved stuff around at the bottom of the tree and
 * we need to fix up the extent records above the changes to reflect
 * the new changes.
 *
 * left_rec: the record on the left.
 * left_child_el: is the child list pointed to by left_rec
 * right_rec: the record to the right of left_rec
 * right_child_el: is the child list pointed to by right_rec
 *
 * By definition, this only works on interior nodes.
 */
static void ocfs2_adjust_adjacent_records(struct ocfs2_extent_rec *left_rec,
                  struct ocfs2_extent_list *left_child_el,
                  struct ocfs2_extent_rec *right_rec,
                  struct ocfs2_extent_list *right_child_el)
{
    u32 left_clusters, right_end;

    /*
     * Interior nodes never have holes. Their cpos is the cpos of
     * the leftmost record in their child list. Their cluster
     * count covers the full theoretical range of their child list
     * - the range between their cpos and the cpos of the record
     * immediately to their right.
     */
    left_clusters = le32_to_cpu(right_child_el->l_recs[0].e_cpos);
    if (!ocfs2_rec_clusters(right_child_el, &right_child_el->l_recs[0])) {
        BUG_ON(right_child_el->l_tree_depth);
        BUG_ON(le16_to_cpu(right_child_el->l_next_free_rec) <= 1);
        left_clusters = le32_to_cpu(right_child_el->l_recs[1].e_cpos);
    }
    left_clusters -= le32_to_cpu(left_rec->e_cpos);
    left_rec->e_int_clusters = cpu_to_le32(left_clusters);

    /*
     * Calculate the rightmost cluster count boundary before
     * moving cpos - we will need to adjust clusters after
     * updating e_cpos to keep the same highest cluster count.
     */
    right_end = le32_to_cpu(right_rec->e_cpos);
    right_end += le32_to_cpu(right_rec->e_int_clusters);

    right_rec->e_cpos = left_rec->e_cpos;
    le32_add_cpu(&right_rec->e_cpos, left_clusters);

    right_end -= le32_to_cpu(right_rec->e_cpos);
    right_rec->e_int_clusters = cpu_to_le32(right_end);
}

/*
 * Adjust the adjacent root node records involved in a
 * rotation. left_el_blkno is passed in as a key so that we can easily
 * find it's index in the root list.
 */
static void ocfs2_adjust_root_records(struct ocfs2_extent_list *root_el,
                      struct ocfs2_extent_list *left_el,
                      struct ocfs2_extent_list *right_el,
                      u64 left_el_blkno)
{
    int i;

    BUG_ON(le16_to_cpu(root_el->l_tree_depth) <=
           le16_to_cpu(left_el->l_tree_depth));

    for(i = 0; i < le16_to_cpu(root_el->l_next_free_rec) - 1; i++) {
        if (le64_to_cpu(root_el->l_recs[i].e_blkno) == left_el_blkno)
            break;
    }

    /*
     * The path walking code should have never returned a root and
     * two paths which are not adjacent.
     */
    BUG_ON(i >= (le16_to_cpu(root_el->l_next_free_rec) - 1));

    ocfs2_adjust_adjacent_records(&root_el->l_recs[i], left_el,
                      &root_el->l_recs[i + 1], right_el);
}

/*
 * We've changed a leaf block (in right_path) and need to reflect that
 * change back up the subtree.
 *
 * This happens in multiple places:
 *   - When we've moved an extent record from the left path leaf to the right
 *     path leaf to make room for an empty extent in the left path leaf.
 *   - When our insert into the right path leaf is at the leftmost edge
 *     and requires an update of the path immediately to it's left. This
 *     can occur at the end of some types of rotation and appending inserts.
 *   - When we've adjusted the last extent record in the left path leaf and the
 *     1st extent record in the right path leaf during cross extent block merge.
 */
static void ocfs2_complete_edge_insert(handle_t *handle,
                       struct ocfs2_path *left_path,
                       struct ocfs2_path *right_path,
                       int subtree_index)
{
    int i, idx;
    struct ocfs2_extent_list *el, *left_el, *right_el;
    struct ocfs2_extent_rec *left_rec, *right_rec;
    struct buffer_head *root_bh = left_path->p_node[subtree_index].bh;

    /*
     * Update the counts and position values within all the
     * interior nodes to reflect the leaf rotation we just did.
     *
     * The root node is handled below the loop.
     *
     * We begin the loop with right_el and left_el pointing to the
     * leaf lists and work our way up.
     *
     * NOTE: within this loop, left_el and right_el always refer
     * to the *child* lists.
     */
    left_el = path_leaf_el(left_path);
    right_el = path_leaf_el(right_path);
    for(i = left_path->p_tree_depth - 1; i > subtree_index; i--) {
        trace_ocfs2_complete_edge_insert(i);

        /*
         * One nice property of knowing that all of these
         * nodes are below the root is that we only deal with
         * the leftmost right node record and the rightmost
         * left node record.
         */
        el = left_path->p_node[i].el;
        idx = le16_to_cpu(left_el->l_next_free_rec) - 1;
        left_rec = &el->l_recs[idx];

        el = right_path->p_node[i].el;
        right_rec = &el->l_recs[0];

        ocfs2_adjust_adjacent_records(left_rec, left_el, right_rec,
                          right_el);

        ocfs2_journal_dirty(handle, left_path->p_node[i].bh);
        ocfs2_journal_dirty(handle, right_path->p_node[i].bh);

        /*
         * Setup our list pointers now so that the current
         * parents become children in the next iteration.
         */
        left_el = left_path->p_node[i].el;
        right_el = right_path->p_node[i].el;
    }

    /*
     * At the root node, adjust the two adjacent records which
     * begin our path to the leaves.
     */

    el = left_path->p_node[subtree_index].el;
    left_el = left_path->p_node[subtree_index + 1].el;
    right_el = right_path->p_node[subtree_index + 1].el;

    ocfs2_adjust_root_records(el, left_el, right_el,
                  left_path->p_node[subtree_index + 1].bh->b_blocknr);

    root_bh = left_path->p_node[subtree_index].bh;

    ocfs2_journal_dirty(handle, root_bh);
}

static int ocfs2_rotate_subtree_right(handle_t *handle,
                      struct ocfs2_extent_tree *et,
                      struct ocfs2_path *left_path,
                      struct ocfs2_path *right_path,
                      int subtree_index)
{
    int ret, i;
    struct buffer_head *right_leaf_bh;
    struct buffer_head *left_leaf_bh = NULL;
    struct buffer_head *root_bh;
    struct ocfs2_extent_list *right_el, *left_el;
    struct ocfs2_extent_rec move_rec;

    left_leaf_bh = path_leaf_bh(left_path);
    left_el = path_leaf_el(left_path);

    if (left_el->l_next_free_rec != left_el->l_count) {
        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                "Inode %llu has non-full interior leaf node %llu"
                "(next free = %u)",
                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                (unsigned long long)left_leaf_bh->b_blocknr,
                le16_to_cpu(left_el->l_next_free_rec));
        return -EROFS;
    }

    /*
     * This extent block may already have an empty record, so we
     * return early if so.
     */
    if (ocfs2_is_empty_extent(&left_el->l_recs[0]))
        return 0;

    root_bh = left_path->p_node[subtree_index].bh;
    BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                       subtree_index);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    for(i = subtree_index + 1; i < path_num_items(right_path); i++) {
        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                           right_path, i);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                           left_path, i);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    right_leaf_bh = path_leaf_bh(right_path);
    right_el = path_leaf_el(right_path);

    /* This is a code error, not a disk corruption. */
    mlog_bug_on_msg(!right_el->l_next_free_rec, "Inode %llu: Rotate fails "
            "because rightmost leaf block %llu is empty\n",
            (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
            (unsigned long long)right_leaf_bh->b_blocknr);

    ocfs2_create_empty_extent(right_el);

    ocfs2_journal_dirty(handle, right_leaf_bh);

    /* Do the copy now. */
    i = le16_to_cpu(left_el->l_next_free_rec) - 1;
    move_rec = left_el->l_recs[i];
    right_el->l_recs[0] = move_rec;

    /*
     * Clear out the record we just copied and shift everything
     * over, leaving an empty extent in the left leaf.
     *
     * We temporarily subtract from next_free_rec so that the
     * shift will lose the tail record (which is now defunct).
     */
    le16_add_cpu(&left_el->l_next_free_rec, -1);
    ocfs2_shift_records_right(left_el);
    memset(&left_el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
    le16_add_cpu(&left_el->l_next_free_rec, 1);

    ocfs2_journal_dirty(handle, left_leaf_bh);

    ocfs2_complete_edge_insert(handle, left_path, right_path,
                   subtree_index);

out:
    return ret;
}

/*
 * Given a full path, determine what cpos value would return us a path
 * containing the leaf immediately to the left of the current one.
 *
 * Will return zero if the path passed in is already the leftmost path.
 */
int ocfs2_find_cpos_for_left_leaf(struct super_block *sb,
                  struct ocfs2_path *path, u32 *cpos)
{
    int i, j, ret = 0;
    u64 blkno;
    struct ocfs2_extent_list *el;

    BUG_ON(path->p_tree_depth == 0);

    *cpos = 0;

    blkno = path_leaf_bh(path)->b_blocknr;

    /* Start at the tree node just above the leaf and work our way up. */
    i = path->p_tree_depth - 1;
    while (i >= 0) {
        el = path->p_node[i].el;

        /*
         * Find the extent record just before the one in our
         * path.
         */
        for(j = 0; j < le16_to_cpu(el->l_next_free_rec); j++) {
            if (le64_to_cpu(el->l_recs[j].e_blkno) == blkno) {
                if (j == 0) {
                    if (i == 0) {
                        /*
                         * We've determined that the
                         * path specified is already
                         * the leftmost one - return a
                         * cpos of zero.
                         */
                        goto out;
                    }
                    /*
                     * The leftmost record points to our
                     * leaf - we need to travel up the
                     * tree one level.
                     */
                    goto next_node;
                }

                *cpos = le32_to_cpu(el->l_recs[j - 1].e_cpos);
                *cpos = *cpos + ocfs2_rec_clusters(el,
                               &el->l_recs[j - 1]);
                *cpos = *cpos - 1;
                goto out;
            }
        }

        /*
         * If we got here, we never found a valid node where
         * the tree indicated one should be.
         */
        ocfs2_error(sb,
                "Invalid extent tree at extent block %llu\n",
                (unsigned long long)blkno);
        ret = -EROFS;
        goto out;

next_node:
        blkno = path->p_node[i].bh->b_blocknr;
        i--;
    }

out:
    return ret;
}

/*
 * Extend the transaction by enough credits to complete the rotation,
 * and still leave at least the original number of credits allocated
 * to this transaction.
 */
static int ocfs2_extend_rotate_transaction(handle_t *handle, int subtree_depth,
                       int op_credits,
                       struct ocfs2_path *path)
{
    int ret = 0;
    int credits = (path->p_tree_depth - subtree_depth) * 2 + 1 + op_credits;

    if (handle->h_buffer_credits < credits)
        ret = ocfs2_extend_trans(handle,
                     credits - handle->h_buffer_credits);

    return ret;
}

/*
 * Trap the case where we're inserting into the theoretical range past
 * the _actual_ left leaf range. Otherwise, we'll rotate a record
 * whose cpos is less than ours into the right leaf.
 *
 * It's only necessary to look at the rightmost record of the left
 * leaf because the logic that calls us should ensure that the
 * theoretical ranges in the path components above the leaves are
 * correct.
 */
static int ocfs2_rotate_requires_path_adjustment(struct ocfs2_path *left_path,
                         u32 insert_cpos)
{
    struct ocfs2_extent_list *left_el;
    struct ocfs2_extent_rec *rec;
    int next_free;

    left_el = path_leaf_el(left_path);
    next_free = le16_to_cpu(left_el->l_next_free_rec);
    rec = &left_el->l_recs[next_free - 1];

    if (insert_cpos > le32_to_cpu(rec->e_cpos))
        return 1;
    return 0;
}

static int ocfs2_leftmost_rec_contains(struct ocfs2_extent_list *el, u32 cpos)
{
    int next_free = le16_to_cpu(el->l_next_free_rec);
    unsigned int range;
    struct ocfs2_extent_rec *rec;

    if (next_free == 0)
        return 0;

    rec = &el->l_recs[0];
    if (ocfs2_is_empty_extent(rec)) {
        /* Empty list. */
        if (next_free == 1)
            return 0;
        rec = &el->l_recs[1];
    }

    range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
    if (cpos >= le32_to_cpu(rec->e_cpos) && cpos < range)
        return 1;
    return 0;
}

/*
 * Rotate all the records in a btree right one record, starting at insert_cpos.
 *
 * The path to the rightmost leaf should be passed in.
 *
 * The array is assumed to be large enough to hold an entire path (tree depth).
 *
 * Upon successful return from this function:
 *
 * - The 'right_path' array will contain a path to the leaf block
 *   whose range contains e_cpos.
 * - That leaf block will have a single empty extent in list index 0.
 * - In the case that the rotation requires a post-insert update,
 *   *ret_left_path will contain a valid path which can be passed to
 *   ocfs2_insert_path().
 */
static int ocfs2_rotate_tree_right(handle_t *handle,
                   struct ocfs2_extent_tree *et,
                   enum ocfs2_split_type split,
                   u32 insert_cpos,
                   struct ocfs2_path *right_path,
                   struct ocfs2_path **ret_left_path)
{
    int ret, start, orig_credits = handle->h_buffer_credits;
    u32 cpos;
    struct ocfs2_path *left_path = NULL;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);

    *ret_left_path = NULL;

    left_path = ocfs2_new_path_from_path(right_path);
    if (!left_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_cpos_for_left_leaf(sb, right_path, &cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_rotate_tree_right(
        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
        insert_cpos, cpos);

    /*
     * What we want to do here is:
     *
     * 1) Start with the rightmost path.
     *
     * 2) Determine a path to the leaf block directly to the left
     *    of that leaf.
     *
     * 3) Determine the 'subtree root' - the lowest level tree node
     *    which contains a path to both leaves.
     *
     * 4) Rotate the subtree.
     *
     * 5) Find the next subtree by considering the left path to be
     *    the new right path.
     *
     * The check at the top of this while loop also accepts
     * insert_cpos == cpos because cpos is only a _theoretical_
     * value to get us the left path - insert_cpos might very well
     * be filling that hole.
     *
     * Stop at a cpos of '0' because we either started at the
     * leftmost branch (i.e., a tree with one branch and a
     * rotation inside of it), or we've gone as far as we can in
     * rotating subtrees.
     */
    while (cpos && insert_cpos <= cpos) {
        trace_ocfs2_rotate_tree_right(
            (unsigned long long)
            ocfs2_metadata_cache_owner(et->et_ci),
            insert_cpos, cpos);

        ret = ocfs2_find_path(et->et_ci, left_path, cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        mlog_bug_on_msg(path_leaf_bh(left_path) ==
                path_leaf_bh(right_path),
                "Owner %llu: error during insert of %u "
                "(left path cpos %u) results in two identical "
                "paths ending at %llu\n",
                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                insert_cpos, cpos,
                (unsigned long long)
                path_leaf_bh(left_path)->b_blocknr);

        if (split == SPLIT_NONE &&
            ocfs2_rotate_requires_path_adjustment(left_path,
                              insert_cpos)) {

            /*
             * We've rotated the tree as much as we
             * should. The rest is up to
             * ocfs2_insert_path() to complete, after the
             * record insertion. We indicate this
             * situation by returning the left path.
             *
             * The reason we don't adjust the records here
             * before the record insert is that an error
             * later might break the rule where a parent
             * record e_cpos will reflect the actual
             * e_cpos of the 1st nonempty record of the
             * child list.
             */
            *ret_left_path = left_path;
            goto out_ret_path;
        }

        start = ocfs2_find_subtree_root(et, left_path, right_path);

        trace_ocfs2_rotate_subtree(start,
            (unsigned long long)
            right_path->p_node[start].bh->b_blocknr,
            right_path->p_tree_depth);

        ret = ocfs2_extend_rotate_transaction(handle, start,
                              orig_credits, right_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_rotate_subtree_right(handle, et, left_path,
                         right_path, start);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (split != SPLIT_NONE &&
            ocfs2_leftmost_rec_contains(path_leaf_el(right_path),
                        insert_cpos)) {
            /*
             * A rotate moves the rightmost left leaf
             * record over to the leftmost right leaf
             * slot. If we're doing an extent split
             * instead of a real insert, then we have to
             * check that the extent to be split wasn't
             * just moved over. If it was, then we can
             * exit here, passing left_path back -
             * ocfs2_split_extent() is smart enough to
             * search both leaves.
             */
            *ret_left_path = left_path;
            goto out_ret_path;
        }

        /*
         * There is no need to re-read the next right path
         * as we know that it'll be our current left
         * path. Optimize by copying values instead.
         */
        ocfs2_mv_path(right_path, left_path);

        ret = ocfs2_find_cpos_for_left_leaf(sb, right_path, &cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

out:
    ocfs2_free_path(left_path);

out_ret_path:
    return ret;
}

static int ocfs2_update_edge_lengths(handle_t *handle,
                     struct ocfs2_extent_tree *et,
                     int subtree_index, struct ocfs2_path *path)
{
    int i, idx, ret;
    struct ocfs2_extent_rec *rec;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_block *eb;
    u32 range;

    /*
     * In normal tree rotation process, we will never touch the
     * tree branch above subtree_index and ocfs2_extend_rotate_transaction
     * doesn't reserve the credits for them either.
     *
     * But we do have a special case here which will update the rightmost
     * records for all the bh in the path.
     * So we have to allocate extra credits and access them.
     */
    ret = ocfs2_extend_trans(handle, subtree_index);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_path(et->et_ci, handle, path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /* Path should always be rightmost. */
    eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
    BUG_ON(eb->h_next_leaf_blk != 0ULL);

    el = &eb->h_list;
    BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);
    idx = le16_to_cpu(el->l_next_free_rec) - 1;
    rec = &el->l_recs[idx];
    range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);

    for (i = 0; i < path->p_tree_depth; i++) {
        el = path->p_node[i].el;
        idx = le16_to_cpu(el->l_next_free_rec) - 1;
        rec = &el->l_recs[idx];

        rec->e_int_clusters = cpu_to_le32(range);
        le32_add_cpu(&rec->e_int_clusters, -le32_to_cpu(rec->e_cpos));

        ocfs2_journal_dirty(handle, path->p_node[i].bh);
    }
out:
    return ret;
}

static void ocfs2_unlink_path(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_cached_dealloc_ctxt *dealloc,
                  struct ocfs2_path *path, int unlink_start)
{
    int ret, i;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *el;
    struct buffer_head *bh;

    for(i = unlink_start; i < path_num_items(path); i++) {
        bh = path->p_node[i].bh;

        eb = (struct ocfs2_extent_block *)bh->b_data;
        /*
         * Not all nodes might have had their final count
         * decremented by the caller - handle this here.
         */
        el = &eb->h_list;
        if (le16_to_cpu(el->l_next_free_rec) > 1) {
            mlog(ML_ERROR,
                 "Inode %llu, attempted to remove extent block "
                 "%llu with %u records\n",
                 (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                 (unsigned long long)le64_to_cpu(eb->h_blkno),
                 le16_to_cpu(el->l_next_free_rec));

            ocfs2_journal_dirty(handle, bh);
            ocfs2_remove_from_cache(et->et_ci, bh);
            continue;
        }

        el->l_next_free_rec = 0;
        memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));

        ocfs2_journal_dirty(handle, bh);

        ret = ocfs2_cache_extent_block_free(dealloc, eb);
        if (ret)
            mlog_errno(ret);

        ocfs2_remove_from_cache(et->et_ci, bh);
    }
}

static void ocfs2_unlink_subtree(handle_t *handle,
                 struct ocfs2_extent_tree *et,
                 struct ocfs2_path *left_path,
                 struct ocfs2_path *right_path,
                 int subtree_index,
                 struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int i;
    struct buffer_head *root_bh = left_path->p_node[subtree_index].bh;
    struct ocfs2_extent_list *root_el = left_path->p_node[subtree_index].el;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_block *eb;

    el = path_leaf_el(left_path);

    eb = (struct ocfs2_extent_block *)right_path->p_node[subtree_index + 1].bh->b_data;

    for(i = 1; i < le16_to_cpu(root_el->l_next_free_rec); i++)
        if (root_el->l_recs[i].e_blkno == eb->h_blkno)
            break;

    BUG_ON(i >= le16_to_cpu(root_el->l_next_free_rec));

    memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
    le16_add_cpu(&root_el->l_next_free_rec, -1);

    eb = (struct ocfs2_extent_block *)path_leaf_bh(left_path)->b_data;
    eb->h_next_leaf_blk = 0;

    ocfs2_journal_dirty(handle, root_bh);
    ocfs2_journal_dirty(handle, path_leaf_bh(left_path));

    ocfs2_unlink_path(handle, et, dealloc, right_path,
              subtree_index + 1);
}

static int ocfs2_rotate_subtree_left(handle_t *handle,
                     struct ocfs2_extent_tree *et,
                     struct ocfs2_path *left_path,
                     struct ocfs2_path *right_path,
                     int subtree_index,
                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                     int *deleted)
{
    int ret, i, del_right_subtree = 0, right_has_empty = 0;
    struct buffer_head *root_bh, *et_root_bh = path_root_bh(right_path);
    struct ocfs2_extent_list *right_leaf_el, *left_leaf_el;
    struct ocfs2_extent_block *eb;

    *deleted = 0;

    right_leaf_el = path_leaf_el(right_path);
    left_leaf_el = path_leaf_el(left_path);
    root_bh = left_path->p_node[subtree_index].bh;
    BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

    if (!ocfs2_is_empty_extent(&left_leaf_el->l_recs[0]))
        return 0;

    eb = (struct ocfs2_extent_block *)path_leaf_bh(right_path)->b_data;
    if (ocfs2_is_empty_extent(&right_leaf_el->l_recs[0])) {
        /*
         * It's legal for us to proceed if the right leaf is
         * the rightmost one and it has an empty extent. There
         * are two cases to handle - whether the leaf will be
         * empty after removal or not. If the leaf isn't empty
         * then just remove the empty extent up front. The
         * next block will handle empty leaves by flagging
         * them for unlink.
         *
         * Non rightmost leaves will throw -EAGAIN and the
         * caller can manually move the subtree and retry.
         */

        if (eb->h_next_leaf_blk != 0ULL)
            return -EAGAIN;

        if (le16_to_cpu(right_leaf_el->l_next_free_rec) > 1) {
            ret = ocfs2_journal_access_eb(handle, et->et_ci,
                              path_leaf_bh(right_path),
                              OCFS2_JOURNAL_ACCESS_WRITE);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            ocfs2_remove_empty_extent(right_leaf_el);
        } else
            right_has_empty = 1;
    }

    if (eb->h_next_leaf_blk == 0ULL &&
        le16_to_cpu(right_leaf_el->l_next_free_rec) == 1) {
        /*
         * We have to update i_last_eb_blk during the meta
         * data delete.
         */
        ret = ocfs2_et_root_journal_access(handle, et,
                           OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        del_right_subtree = 1;
    }

    /*
     * Getting here with an empty extent in the right path implies
     * that it's the rightmost path and will be deleted.
     */
    BUG_ON(right_has_empty && !del_right_subtree);

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                       subtree_index);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    for(i = subtree_index + 1; i < path_num_items(right_path); i++) {
        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                           right_path, i);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                           left_path, i);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    if (!right_has_empty) {
        /*
         * Only do this if we're moving a real
         * record. Otherwise, the action is delayed until
         * after removal of the right path in which case we
         * can do a simple shift to remove the empty extent.
         */
        ocfs2_rotate_leaf(left_leaf_el, &right_leaf_el->l_recs[0]);
        memset(&right_leaf_el->l_recs[0], 0,
               sizeof(struct ocfs2_extent_rec));
    }
    if (eb->h_next_leaf_blk == 0ULL) {
        /*
         * Move recs over to get rid of empty extent, decrease
         * next_free. This is allowed to remove the last
         * extent in our leaf (setting l_next_free_rec to
         * zero) - the delete code below won't care.
         */
        ocfs2_remove_empty_extent(right_leaf_el);
    }

    ocfs2_journal_dirty(handle, path_leaf_bh(left_path));
    ocfs2_journal_dirty(handle, path_leaf_bh(right_path));

    if (del_right_subtree) {
        ocfs2_unlink_subtree(handle, et, left_path, right_path,
                     subtree_index, dealloc);
        ret = ocfs2_update_edge_lengths(handle, et, subtree_index,
                        left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        eb = (struct ocfs2_extent_block *)path_leaf_bh(left_path)->b_data;
        ocfs2_et_set_last_eb_blk(et, le64_to_cpu(eb->h_blkno));

        /*
         * Removal of the extent in the left leaf was skipped
         * above so we could delete the right path
         * 1st.
         */
        if (right_has_empty)
            ocfs2_remove_empty_extent(left_leaf_el);

        ocfs2_journal_dirty(handle, et_root_bh);

        *deleted = 1;
    } else
        ocfs2_complete_edge_insert(handle, left_path, right_path,
                       subtree_index);

out:
    return ret;
}

/*
 * Given a full path, determine what cpos value would return us a path
 * containing the leaf immediately to the right of the current one.
 *
 * Will return zero if the path passed in is already the rightmost path.
 *
 * This looks similar, but is subtly different to
 * ocfs2_find_cpos_for_left_leaf().
 */
int ocfs2_find_cpos_for_right_leaf(struct super_block *sb,
                   struct ocfs2_path *path, u32 *cpos)
{
    int i, j, ret = 0;
    u64 blkno;
    struct ocfs2_extent_list *el;

    *cpos = 0;

    if (path->p_tree_depth == 0)
        return 0;

    blkno = path_leaf_bh(path)->b_blocknr;

    /* Start at the tree node just above the leaf and work our way up. */
    i = path->p_tree_depth - 1;
    while (i >= 0) {
        int next_free;

        el = path->p_node[i].el;

        /*
         * Find the extent record just after the one in our
         * path.
         */
        next_free = le16_to_cpu(el->l_next_free_rec);
        for(j = 0; j < le16_to_cpu(el->l_next_free_rec); j++) {
            if (le64_to_cpu(el->l_recs[j].e_blkno) == blkno) {
                if (j == (next_free - 1)) {
                    if (i == 0) {
                        /*
                         * We've determined that the
                         * path specified is already
                         * the rightmost one - return a
                         * cpos of zero.
                         */
                        goto out;
                    }
                    /*
                     * The rightmost record points to our
                     * leaf - we need to travel up the
                     * tree one level.
                     */
                    goto next_node;
                }

                *cpos = le32_to_cpu(el->l_recs[j + 1].e_cpos);
                goto out;
            }
        }

        /*
         * If we got here, we never found a valid node where
         * the tree indicated one should be.
         */
        ocfs2_error(sb,
                "Invalid extent tree at extent block %llu\n",
                (unsigned long long)blkno);
        ret = -EROFS;
        goto out;

next_node:
        blkno = path->p_node[i].bh->b_blocknr;
        i--;
    }

out:
    return ret;
}

static int ocfs2_rotate_rightmost_leaf_left(handle_t *handle,
                        struct ocfs2_extent_tree *et,
                        struct ocfs2_path *path)
{
    int ret;
    struct buffer_head *bh = path_leaf_bh(path);
    struct ocfs2_extent_list *el = path_leaf_el(path);

    if (!ocfs2_is_empty_extent(&el->l_recs[0]))
        return 0;

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, path,
                       path_num_items(path) - 1);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_remove_empty_extent(el);
    ocfs2_journal_dirty(handle, bh);

out:
    return ret;
}

static int __ocfs2_rotate_tree_left(handle_t *handle,
                    struct ocfs2_extent_tree *et,
                    int orig_credits,
                    struct ocfs2_path *path,
                    struct ocfs2_cached_dealloc_ctxt *dealloc,
                    struct ocfs2_path **empty_extent_path)
{
    int ret, subtree_root, deleted;
    u32 right_cpos;
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_path *right_path = NULL;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);

    BUG_ON(!ocfs2_is_empty_extent(&(path_leaf_el(path)->l_recs[0])));

    *empty_extent_path = NULL;

    ret = ocfs2_find_cpos_for_right_leaf(sb, path, &right_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    left_path = ocfs2_new_path_from_path(path);
    if (!left_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ocfs2_cp_path(left_path, path);

    right_path = ocfs2_new_path_from_path(path);
    if (!right_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    while (right_cpos) {
        ret = ocfs2_find_path(et->et_ci, right_path, right_cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        subtree_root = ocfs2_find_subtree_root(et, left_path,
                               right_path);

        trace_ocfs2_rotate_subtree(subtree_root,
             (unsigned long long)
             right_path->p_node[subtree_root].bh->b_blocknr,
             right_path->p_tree_depth);

        ret = ocfs2_extend_rotate_transaction(handle, subtree_root,
                              orig_credits, left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * Caller might still want to make changes to the
         * tree root, so re-add it to the journal here.
         */
        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                           left_path, 0);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_rotate_subtree_left(handle, et, left_path,
                        right_path, subtree_root,
                        dealloc, &deleted);
        if (ret == -EAGAIN) {
            /*
             * The rotation has to temporarily stop due to
             * the right subtree having an empty
             * extent. Pass it back to the caller for a
             * fixup.
             */
            *empty_extent_path = right_path;
            right_path = NULL;
            goto out;
        }
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * The subtree rotate might have removed records on
         * the rightmost edge. If so, then rotation is
         * complete.
         */
        if (deleted)
            break;

        ocfs2_mv_path(left_path, right_path);

        ret = ocfs2_find_cpos_for_right_leaf(sb, left_path,
                             &right_cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

out:
    ocfs2_free_path(right_path);
    ocfs2_free_path(left_path);

    return ret;
}

static int ocfs2_remove_rightmost_path(handle_t *handle,
                struct ocfs2_extent_tree *et,
                struct ocfs2_path *path,
                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret, subtree_index;
    u32 cpos;
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *el;


    ret = ocfs2_et_sanity_check(et);
    if (ret)
        goto out;
    /*
     * There's two ways we handle this depending on
     * whether path is the only existing one.
     */
    ret = ocfs2_extend_rotate_transaction(handle, 0,
                          handle->h_buffer_credits,
                          path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_path(et->et_ci, handle, path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                        path, &cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (cpos) {
        /*
         * We have a path to the left of this one - it needs
         * an update too.
         */
        left_path = ocfs2_new_path_from_path(path);
        if (!left_path) {
            ret = -ENOMEM;
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_find_path(et->et_ci, left_path, cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_journal_access_path(et->et_ci, handle, left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        subtree_index = ocfs2_find_subtree_root(et, left_path, path);

        ocfs2_unlink_subtree(handle, et, left_path, path,
                     subtree_index, dealloc);
        ret = ocfs2_update_edge_lengths(handle, et, subtree_index,
                        left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        eb = (struct ocfs2_extent_block *)path_leaf_bh(left_path)->b_data;
        ocfs2_et_set_last_eb_blk(et, le64_to_cpu(eb->h_blkno));
    } else {
        /*
         * 'path' is also the leftmost path which
         * means it must be the only one. This gets
         * handled differently because we want to
         * revert the root back to having extents
         * in-line.
         */
        ocfs2_unlink_path(handle, et, dealloc, path, 1);

        el = et->et_root_el;
        el->l_tree_depth = 0;
        el->l_next_free_rec = 0;
        memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));

        ocfs2_et_set_last_eb_blk(et, 0);
    }

    ocfs2_journal_dirty(handle, path_root_bh(path));

out:
    ocfs2_free_path(left_path);
    return ret;
}

/*
 * Left rotation of btree records.
 *
 * In many ways, this is (unsurprisingly) the opposite of right
 * rotation. We start at some non-rightmost path containing an empty
 * extent in the leaf block. The code works its way to the rightmost
 * path by rotating records to the left in every subtree.
 *
 * This is used by any code which reduces the number of extent records
 * in a leaf. After removal, an empty record should be placed in the
 * leftmost list position.
 *
 * This won't handle a length update of the rightmost path records if
 * the rightmost tree leaf record is removed so the caller is
 * responsible for detecting and correcting that.
 */
static int ocfs2_rotate_tree_left(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_path *path,
                  struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret, orig_credits = handle->h_buffer_credits;
    struct ocfs2_path *tmp_path = NULL, *restart_path = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *el;

    el = path_leaf_el(path);
    if (!ocfs2_is_empty_extent(&el->l_recs[0]))
        return 0;

    if (path->p_tree_depth == 0) {
rightmost_no_delete:
        /*
         * Inline extents. This is trivially handled, so do
         * it up front.
         */
        ret = ocfs2_rotate_rightmost_leaf_left(handle, et, path);
        if (ret)
            mlog_errno(ret);
        goto out;
    }

    /*
     * Handle rightmost branch now. There's several cases:
     *  1) simple rotation leaving records in there. That's trivial.
     *  2) rotation requiring a branch delete - there's no more
     *     records left. Two cases of this:
     *     a) There are branches to the left.
     *     b) This is also the leftmost (the only) branch.
     *
     *  1) is handled via ocfs2_rotate_rightmost_leaf_left()
     *  2a) we need the left branch so that we can update it with the unlink
     *  2b) we need to bring the root back to inline extents.
     */

    eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
    el = &eb->h_list;
    if (eb->h_next_leaf_blk == 0) {
        /*
         * This gets a bit tricky if we're going to delete the
         * rightmost path. Get the other cases out of the way
         * 1st.
         */
        if (le16_to_cpu(el->l_next_free_rec) > 1)
            goto rightmost_no_delete;

        if (le16_to_cpu(el->l_next_free_rec) == 0) {
            ret = -EIO;
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu has empty extent block at %llu",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                    (unsigned long long)le64_to_cpu(eb->h_blkno));
            goto out;
        }

        /*
         * XXX: The caller can not trust "path" any more after
         * this as it will have been deleted. What do we do?
         *
         * In theory the rotate-for-merge code will never get
         * here because it'll always ask for a rotate in a
         * nonempty list.
         */

        ret = ocfs2_remove_rightmost_path(handle, et, path,
                          dealloc);
        if (ret)
            mlog_errno(ret);
        goto out;
    }

    /*
     * Now we can loop, remembering the path we get from -EAGAIN
     * and restarting from there.
     */
try_rotate:
    ret = __ocfs2_rotate_tree_left(handle, et, orig_credits, path,
                       dealloc, &restart_path);
    if (ret && ret != -EAGAIN) {
        mlog_errno(ret);
        goto out;
    }

    while (ret == -EAGAIN) {
        tmp_path = restart_path;
        restart_path = NULL;

        ret = __ocfs2_rotate_tree_left(handle, et, orig_credits,
                           tmp_path, dealloc,
                           &restart_path);
        if (ret && ret != -EAGAIN) {
            mlog_errno(ret);
            goto out;
        }

        ocfs2_free_path(tmp_path);
        tmp_path = NULL;

        if (ret == 0)
            goto try_rotate;
    }

out:
    ocfs2_free_path(tmp_path);
    ocfs2_free_path(restart_path);
    return ret;
}

static void ocfs2_cleanup_merge(struct ocfs2_extent_list *el,
                int index)
{
    struct ocfs2_extent_rec *rec = &el->l_recs[index];
    unsigned int size;

    if (rec->e_leaf_clusters == 0) {
        /*
         * We consumed all of the merged-from record. An empty
         * extent cannot exist anywhere but the 1st array
         * position, so move things over if the merged-from
         * record doesn't occupy that position.
         *
         * This creates a new empty extent so the caller
         * should be smart enough to have removed any existing
         * ones.
         */
        if (index > 0) {
            BUG_ON(ocfs2_is_empty_extent(&el->l_recs[0]));
            size = index * sizeof(struct ocfs2_extent_rec);
            memmove(&el->l_recs[1], &el->l_recs[0], size);
        }

        /*
         * Always memset - the caller doesn't check whether it
         * created an empty extent, so there could be junk in
         * the other fields.
         */
        memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
    }
}

static int ocfs2_get_right_path(struct ocfs2_extent_tree *et,
                struct ocfs2_path *left_path,
                struct ocfs2_path **ret_right_path)
{
    int ret;
    u32 right_cpos;
    struct ocfs2_path *right_path = NULL;
    struct ocfs2_extent_list *left_el;

    *ret_right_path = NULL;

    /* This function shouldn't be called for non-trees. */
    BUG_ON(left_path->p_tree_depth == 0);

    left_el = path_leaf_el(left_path);
    BUG_ON(left_el->l_next_free_rec != left_el->l_count);

    ret = ocfs2_find_cpos_for_right_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                         left_path, &right_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /* This function shouldn't be called for the rightmost leaf. */
    BUG_ON(right_cpos == 0);

    right_path = ocfs2_new_path_from_path(left_path);
    if (!right_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_path(et->et_ci, right_path, right_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    *ret_right_path = right_path;
out:
    if (ret)
        ocfs2_free_path(right_path);
    return ret;
}

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the beginning of the record "next" to it.
 * For index < l_count - 1, the next means the extent rec at index + 1.
 * For index == l_count - 1, the "next" means the 1st extent rec of the
 * next extent block.
 */
static int ocfs2_merge_rec_right(struct ocfs2_path *left_path,
                 handle_t *handle,
                 struct ocfs2_extent_tree *et,
                 struct ocfs2_extent_rec *split_rec,
                 int index)
{
    int ret, next_free, i;
    unsigned int split_clusters = le16_to_cpu(split_rec->e_leaf_clusters);
    struct ocfs2_extent_rec *left_rec;
    struct ocfs2_extent_rec *right_rec;
    struct ocfs2_extent_list *right_el;
    struct ocfs2_path *right_path = NULL;
    int subtree_index = 0;
    struct ocfs2_extent_list *el = path_leaf_el(left_path);
    struct buffer_head *bh = path_leaf_bh(left_path);
    struct buffer_head *root_bh = NULL;

    BUG_ON(index >= le16_to_cpu(el->l_next_free_rec));
    left_rec = &el->l_recs[index];

    if (index == le16_to_cpu(el->l_next_free_rec) - 1 &&
        le16_to_cpu(el->l_next_free_rec) == le16_to_cpu(el->l_count)) {
        /* we meet with a cross extent block merge. */
        ret = ocfs2_get_right_path(et, left_path, &right_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        right_el = path_leaf_el(right_path);
        next_free = le16_to_cpu(right_el->l_next_free_rec);
        BUG_ON(next_free <= 0);
        right_rec = &right_el->l_recs[0];
        if (ocfs2_is_empty_extent(right_rec)) {
            BUG_ON(next_free <= 1);
            right_rec = &right_el->l_recs[1];
        }

        BUG_ON(le32_to_cpu(left_rec->e_cpos) +
               le16_to_cpu(left_rec->e_leaf_clusters) !=
               le32_to_cpu(right_rec->e_cpos));

        subtree_index = ocfs2_find_subtree_root(et, left_path,
                            right_path);

        ret = ocfs2_extend_rotate_transaction(handle, subtree_index,
                              handle->h_buffer_credits,
                              right_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        root_bh = left_path->p_node[subtree_index].bh;
        BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                           subtree_index);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        for (i = subtree_index + 1;
             i < path_num_items(right_path); i++) {
            ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                               right_path, i);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                               left_path, i);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }

    } else {
        BUG_ON(index == le16_to_cpu(el->l_next_free_rec) - 1);
        right_rec = &el->l_recs[index + 1];
    }

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, left_path,
                       path_num_items(left_path) - 1);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    le16_add_cpu(&left_rec->e_leaf_clusters, -split_clusters);

    le32_add_cpu(&right_rec->e_cpos, -split_clusters);
    le64_add_cpu(&right_rec->e_blkno,
             -ocfs2_clusters_to_blocks(ocfs2_metadata_cache_get_super(et->et_ci),
                           split_clusters));
    le16_add_cpu(&right_rec->e_leaf_clusters, split_clusters);

    ocfs2_cleanup_merge(el, index);

    ocfs2_journal_dirty(handle, bh);
    if (right_path) {
        ocfs2_journal_dirty(handle, path_leaf_bh(right_path));
        ocfs2_complete_edge_insert(handle, left_path, right_path,
                       subtree_index);
    }
out:
    if (right_path)
        ocfs2_free_path(right_path);
    return ret;
}

static int ocfs2_get_left_path(struct ocfs2_extent_tree *et,
                   struct ocfs2_path *right_path,
                   struct ocfs2_path **ret_left_path)
{
    int ret;
    u32 left_cpos;
    struct ocfs2_path *left_path = NULL;

    *ret_left_path = NULL;

    /* This function shouldn't be called for non-trees. */
    BUG_ON(right_path->p_tree_depth == 0);

    ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                        right_path, &left_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /* This function shouldn't be called for the leftmost leaf. */
    BUG_ON(left_cpos == 0);

    left_path = ocfs2_new_path_from_path(right_path);
    if (!left_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_path(et->et_ci, left_path, left_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    *ret_left_path = left_path;
out:
    if (ret)
        ocfs2_free_path(left_path);
    return ret;
}

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the tail of the record "before" it.
 * For index > 0, the "before" means the extent rec at index - 1.
 *
 * For index == 0, the "before" means the last record of the previous
 * extent block. And there is also a situation that we may need to
 * remove the rightmost leaf extent block in the right_path and change
 * the right path to indicate the new rightmost path.
 */
static int ocfs2_merge_rec_left(struct ocfs2_path *right_path,
                handle_t *handle,
                struct ocfs2_extent_tree *et,
                struct ocfs2_extent_rec *split_rec,
                struct ocfs2_cached_dealloc_ctxt *dealloc,
                int index)
{
    int ret, i, subtree_index = 0, has_empty_extent = 0;
    unsigned int split_clusters = le16_to_cpu(split_rec->e_leaf_clusters);
    struct ocfs2_extent_rec *left_rec;
    struct ocfs2_extent_rec *right_rec;
    struct ocfs2_extent_list *el = path_leaf_el(right_path);
    struct buffer_head *bh = path_leaf_bh(right_path);
    struct buffer_head *root_bh = NULL;
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_extent_list *left_el;

    BUG_ON(index < 0);

    right_rec = &el->l_recs[index];
    if (index == 0) {
        /* we meet with a cross extent block merge. */
        ret = ocfs2_get_left_path(et, right_path, &left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        left_el = path_leaf_el(left_path);
        BUG_ON(le16_to_cpu(left_el->l_next_free_rec) !=
               le16_to_cpu(left_el->l_count));

        left_rec = &left_el->l_recs[
                le16_to_cpu(left_el->l_next_free_rec) - 1];
        BUG_ON(le32_to_cpu(left_rec->e_cpos) +
               le16_to_cpu(left_rec->e_leaf_clusters) !=
               le32_to_cpu(split_rec->e_cpos));

        subtree_index = ocfs2_find_subtree_root(et, left_path,
                            right_path);

        ret = ocfs2_extend_rotate_transaction(handle, subtree_index,
                              handle->h_buffer_credits,
                              left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        root_bh = left_path->p_node[subtree_index].bh;
        BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                           subtree_index);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        for (i = subtree_index + 1;
             i < path_num_items(right_path); i++) {
            ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                               right_path, i);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                               left_path, i);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }
    } else {
        left_rec = &el->l_recs[index - 1];
        if (ocfs2_is_empty_extent(&el->l_recs[0]))
            has_empty_extent = 1;
    }

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                       path_num_items(right_path) - 1);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (has_empty_extent && index == 1) {
        /*
         * The easy case - we can just plop the record right in.
         */
        *left_rec = *split_rec;

        has_empty_extent = 0;
    } else
        le16_add_cpu(&left_rec->e_leaf_clusters, split_clusters);

    le32_add_cpu(&right_rec->e_cpos, split_clusters);
    le64_add_cpu(&right_rec->e_blkno,
             ocfs2_clusters_to_blocks(ocfs2_metadata_cache_get_super(et->et_ci),
                          split_clusters));
    le16_add_cpu(&right_rec->e_leaf_clusters, -split_clusters);

    ocfs2_cleanup_merge(el, index);

    ocfs2_journal_dirty(handle, bh);
    if (left_path) {
        ocfs2_journal_dirty(handle, path_leaf_bh(left_path));

        /*
         * In the situation that the right_rec is empty and the extent
         * block is empty also,  ocfs2_complete_edge_insert can't handle
         * it and we need to delete the right extent block.
         */
        if (le16_to_cpu(right_rec->e_leaf_clusters) == 0 &&
            le16_to_cpu(el->l_next_free_rec) == 1) {

            ret = ocfs2_remove_rightmost_path(handle, et,
                              right_path,
                              dealloc);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            /* Now the rightmost extent block has been deleted.
             * So we use the new rightmost path.
             */
            ocfs2_mv_path(right_path, left_path);
            left_path = NULL;
        } else
            ocfs2_complete_edge_insert(handle, left_path,
                           right_path, subtree_index);
    }
out:
    if (left_path)
        ocfs2_free_path(left_path);
    return ret;
}

static int ocfs2_try_to_merge_extent(handle_t *handle,
                     struct ocfs2_extent_tree *et,
                     struct ocfs2_path *path,
                     int split_index,
                     struct ocfs2_extent_rec *split_rec,
                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                     struct ocfs2_merge_ctxt *ctxt)
{
    int ret = 0;
    struct ocfs2_extent_list *el = path_leaf_el(path);
    struct ocfs2_extent_rec *rec = &el->l_recs[split_index];

    BUG_ON(ctxt->c_contig_type == CONTIG_NONE);

    if (ctxt->c_split_covers_rec && ctxt->c_has_empty_extent) {
        /*
         * The merge code will need to create an empty
         * extent to take the place of the newly
         * emptied slot. Remove any pre-existing empty
         * extents - having more than one in a leaf is
         * illegal.
         */
        ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
        split_index--;
        rec = &el->l_recs[split_index];
    }

    if (ctxt->c_contig_type == CONTIG_LEFTRIGHT) {
        /*
         * Left-right contig implies this.
         */
        BUG_ON(!ctxt->c_split_covers_rec);

        /*
         * Since the leftright insert always covers the entire
         * extent, this call will delete the insert record
         * entirely, resulting in an empty extent record added to
         * the extent block.
         *
         * Since the adding of an empty extent shifts
         * everything back to the right, there's no need to
         * update split_index here.
         *
         * When the split_index is zero, we need to merge it to the
         * prevoius extent block. It is more efficient and easier
         * if we do merge_right first and merge_left later.
         */
        ret = ocfs2_merge_rec_right(path, handle, et, split_rec,
                        split_index);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * We can only get this from logic error above.
         */
        BUG_ON(!ocfs2_is_empty_extent(&el->l_recs[0]));

        /* The merge left us with an empty extent, remove it. */
        ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        rec = &el->l_recs[split_index];

        /*
         * Note that we don't pass split_rec here on purpose -
         * we've merged it into the rec already.
         */
        ret = ocfs2_merge_rec_left(path, handle, et, rec,
                       dealloc, split_index);

        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
        /*
         * Error from this last rotate is not critical, so
         * print but don't bubble it up.
         */
        if (ret)
            mlog_errno(ret);
        ret = 0;
    } else {
        /*
         * Merge a record to the left or right.
         *
         * 'contig_type' is relative to the existing record,
         * so for example, if we're "right contig", it's to
         * the record on the left (hence the left merge).
         */
        if (ctxt->c_contig_type == CONTIG_RIGHT) {
            ret = ocfs2_merge_rec_left(path, handle, et,
                           split_rec, dealloc,
                           split_index);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        } else {
            ret = ocfs2_merge_rec_right(path, handle,
                            et, split_rec,
                            split_index);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }

        if (ctxt->c_split_covers_rec) {
            /*
             * The merge may have left an empty extent in
             * our leaf. Try to rotate it away.
             */
            ret = ocfs2_rotate_tree_left(handle, et, path,
                             dealloc);
            if (ret)
                mlog_errno(ret);
            ret = 0;
        }
    }

out:
    return ret;
}

static void ocfs2_subtract_from_rec(struct super_block *sb,
                    enum ocfs2_split_type split,
                    struct ocfs2_extent_rec *rec,
                    struct ocfs2_extent_rec *split_rec)
{
    u64 len_blocks;

    len_blocks = ocfs2_clusters_to_blocks(sb,
                le16_to_cpu(split_rec->e_leaf_clusters));

    if (split == SPLIT_LEFT) {
        /*
         * Region is on the left edge of the existing
         * record.
         */
        le32_add_cpu(&rec->e_cpos,
                 le16_to_cpu(split_rec->e_leaf_clusters));
        le64_add_cpu(&rec->e_blkno, len_blocks);
        le16_add_cpu(&rec->e_leaf_clusters,
                 -le16_to_cpu(split_rec->e_leaf_clusters));
    } else {
        /*
         * Region is on the right edge of the existing
         * record.
         */
        le16_add_cpu(&rec->e_leaf_clusters,
                 -le16_to_cpu(split_rec->e_leaf_clusters));
    }
}

/*
 * Do the final bits of extent record insertion at the target leaf
 * list. If this leaf is part of an allocation tree, it is assumed
 * that the tree above has been prepared.
 */
static void ocfs2_insert_at_leaf(struct ocfs2_extent_tree *et,
                 struct ocfs2_extent_rec *insert_rec,
                 struct ocfs2_extent_list *el,
                 struct ocfs2_insert_type *insert)
{
    int i = insert->ins_contig_index;
    unsigned int range;
    struct ocfs2_extent_rec *rec;

    BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

    if (insert->ins_split != SPLIT_NONE) {
        i = ocfs2_search_extent_list(el, le32_to_cpu(insert_rec->e_cpos));
        BUG_ON(i == -1);
        rec = &el->l_recs[i];
        ocfs2_subtract_from_rec(ocfs2_metadata_cache_get_super(et->et_ci),
                    insert->ins_split, rec,
                    insert_rec);
        goto rotate;
    }

    /*
     * Contiguous insert - either left or right.
     */
    if (insert->ins_contig != CONTIG_NONE) {
        rec = &el->l_recs[i];
        if (insert->ins_contig == CONTIG_LEFT) {
            rec->e_blkno = insert_rec->e_blkno;
            rec->e_cpos = insert_rec->e_cpos;
        }
        le16_add_cpu(&rec->e_leaf_clusters,
                 le16_to_cpu(insert_rec->e_leaf_clusters));
        return;
    }

    /*
     * Handle insert into an empty leaf.
     */
    if (le16_to_cpu(el->l_next_free_rec) == 0 ||
        ((le16_to_cpu(el->l_next_free_rec) == 1) &&
         ocfs2_is_empty_extent(&el->l_recs[0]))) {
        el->l_recs[0] = *insert_rec;
        el->l_next_free_rec = cpu_to_le16(1);
        return;
    }

    /*
     * Appending insert.
     */
    if (insert->ins_appending == APPEND_TAIL) {
        i = le16_to_cpu(el->l_next_free_rec) - 1;
        rec = &el->l_recs[i];
        range = le32_to_cpu(rec->e_cpos)
            + le16_to_cpu(rec->e_leaf_clusters);
        BUG_ON(le32_to_cpu(insert_rec->e_cpos) < range);

        mlog_bug_on_msg(le16_to_cpu(el->l_next_free_rec) >=
                le16_to_cpu(el->l_count),
                "owner %llu, depth %u, count %u, next free %u, "
                "rec.cpos %u, rec.clusters %u, "
                "insert.cpos %u, insert.clusters %u\n",
                ocfs2_metadata_cache_owner(et->et_ci),
                le16_to_cpu(el->l_tree_depth),
                le16_to_cpu(el->l_count),
                le16_to_cpu(el->l_next_free_rec),
                le32_to_cpu(el->l_recs[i].e_cpos),
                le16_to_cpu(el->l_recs[i].e_leaf_clusters),
                le32_to_cpu(insert_rec->e_cpos),
                le16_to_cpu(insert_rec->e_leaf_clusters));
        i++;
        el->l_recs[i] = *insert_rec;
        le16_add_cpu(&el->l_next_free_rec, 1);
        return;
    }

rotate:
    /*
     * Ok, we have to rotate.
     *
     * At this point, it is safe to assume that inserting into an
     * empty leaf and appending to a leaf have both been handled
     * above.
     *
     * This leaf needs to have space, either by the empty 1st
     * extent record, or by virtue of an l_next_rec < l_count.
     */
    ocfs2_rotate_leaf(el, insert_rec);
}

static void ocfs2_adjust_rightmost_records(handle_t *handle,
                       struct ocfs2_extent_tree *et,
                       struct ocfs2_path *path,
                       struct ocfs2_extent_rec *insert_rec)
{
    int ret, i, next_free;
    struct buffer_head *bh;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec;

    /*
     * Update everything except the leaf block.
     */
    for (i = 0; i < path->p_tree_depth; i++) {
        bh = path->p_node[i].bh;
        el = path->p_node[i].el;

        next_free = le16_to_cpu(el->l_next_free_rec);
        if (next_free == 0) {
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu has a bad extent list",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci));
            ret = -EIO;
            return;
        }

        rec = &el->l_recs[next_free - 1];

        rec->e_int_clusters = insert_rec->e_cpos;
        le32_add_cpu(&rec->e_int_clusters,
                 le16_to_cpu(insert_rec->e_leaf_clusters));
        le32_add_cpu(&rec->e_int_clusters,
                 -le32_to_cpu(rec->e_cpos));

        ocfs2_journal_dirty(handle, bh);
    }
}

static int ocfs2_append_rec_to_path(handle_t *handle,
                    struct ocfs2_extent_tree *et,
                    struct ocfs2_extent_rec *insert_rec,
                    struct ocfs2_path *right_path,
                    struct ocfs2_path **ret_left_path)
{
    int ret, next_free;
    struct ocfs2_extent_list *el;
    struct ocfs2_path *left_path = NULL;

    *ret_left_path = NULL;

    /*
     * This shouldn't happen for non-trees. The extent rec cluster
     * count manipulation below only works for interior nodes.
     */
    BUG_ON(right_path->p_tree_depth == 0);

    /*
     * If our appending insert is at the leftmost edge of a leaf,
     * then we might need to update the rightmost records of the
     * neighboring path.
     */
    el = path_leaf_el(right_path);
    next_free = le16_to_cpu(el->l_next_free_rec);
    if (next_free == 0 ||
        (next_free == 1 && ocfs2_is_empty_extent(&el->l_recs[0]))) {
        u32 left_cpos;

        ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                            right_path, &left_cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        trace_ocfs2_append_rec_to_path(
            (unsigned long long)
            ocfs2_metadata_cache_owner(et->et_ci),
            le32_to_cpu(insert_rec->e_cpos),
            left_cpos);

        /*
         * No need to worry if the append is already in the
         * leftmost leaf.
         */
        if (left_cpos) {
            left_path = ocfs2_new_path_from_path(right_path);
            if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
            }

            ret = ocfs2_find_path(et->et_ci, left_path,
                          left_cpos);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            /*
             * ocfs2_insert_path() will pass the left_path to the
             * journal for us.
             */
        }
    }

    ret = ocfs2_journal_access_path(et->et_ci, handle, right_path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_adjust_rightmost_records(handle, et, right_path, insert_rec);

    *ret_left_path = left_path;
    ret = 0;
out:
    if (ret != 0)
        ocfs2_free_path(left_path);

    return ret;
}

static void ocfs2_split_record(struct ocfs2_extent_tree *et,
                   struct ocfs2_path *left_path,
                   struct ocfs2_path *right_path,
                   struct ocfs2_extent_rec *split_rec,
                   enum ocfs2_split_type split)
{
    int index;
    u32 cpos = le32_to_cpu(split_rec->e_cpos);
    struct ocfs2_extent_list *left_el = NULL, *right_el, *insert_el, *el;
    struct ocfs2_extent_rec *rec, *tmprec;

    right_el = path_leaf_el(right_path);
    if (left_path)
        left_el = path_leaf_el(left_path);

    el = right_el;
    insert_el = right_el;
    index = ocfs2_search_extent_list(el, cpos);
    if (index != -1) {
        if (index == 0 && left_path) {
            BUG_ON(ocfs2_is_empty_extent(&el->l_recs[0]));

            /*
             * This typically means that the record
             * started in the left path but moved to the
             * right as a result of rotation. We either
             * move the existing record to the left, or we
             * do the later insert there.
             *
             * In this case, the left path should always
             * exist as the rotate code will have passed
             * it back for a post-insert update.
             */

            if (split == SPLIT_LEFT) {
                /*
                 * It's a left split. Since we know
                 * that the rotate code gave us an
                 * empty extent in the left path, we
                 * can just do the insert there.
                 */
                insert_el = left_el;
            } else {
                /*
                 * Right split - we have to move the
                 * existing record over to the left
                 * leaf. The insert will be into the
                 * newly created empty extent in the
                 * right leaf.
                 */
                tmprec = &right_el->l_recs[index];
                ocfs2_rotate_leaf(left_el, tmprec);
                el = left_el;

                memset(tmprec, 0, sizeof(*tmprec));
                index = ocfs2_search_extent_list(left_el, cpos);
                BUG_ON(index == -1);
            }
        }
    } else {
        BUG_ON(!left_path);
        BUG_ON(!ocfs2_is_empty_extent(&left_el->l_recs[0]));
        /*
         * Left path is easy - we can just allow the insert to
         * happen.
         */
        el = left_el;
        insert_el = left_el;
        index = ocfs2_search_extent_list(el, cpos);
        BUG_ON(index == -1);
    }

    rec = &el->l_recs[index];
    ocfs2_subtract_from_rec(ocfs2_metadata_cache_get_super(et->et_ci),
                split, rec, split_rec);
    ocfs2_rotate_leaf(insert_el, split_rec);
}

/*
 * This function only does inserts on an allocation b-tree. For tree
 * depth = 0, ocfs2_insert_at_leaf() is called directly.
 *
 * right_path is the path we want to do the actual insert
 * in. left_path should only be passed in if we need to update that
 * portion of the tree after an edge insert.
 */
static int ocfs2_insert_path(handle_t *handle,
                 struct ocfs2_extent_tree *et,
                 struct ocfs2_path *left_path,
                 struct ocfs2_path *right_path,
                 struct ocfs2_extent_rec *insert_rec,
                 struct ocfs2_insert_type *insert)
{
    int ret, subtree_index;
    struct buffer_head *leaf_bh = path_leaf_bh(right_path);

    if (left_path) {
        /*
         * There's a chance that left_path got passed back to
         * us without being accounted for in the
         * journal. Extend our transaction here to be sure we
         * can change those blocks.
         */
        ret = ocfs2_extend_trans(handle, left_path->p_tree_depth);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_journal_access_path(et->et_ci, handle, left_path);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

    /*
     * Pass both paths to the journal. The majority of inserts
     * will be touching all components anyway.
     */
    ret = ocfs2_journal_access_path(et->et_ci, handle, right_path);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

    if (insert->ins_split != SPLIT_NONE) {
        /*
         * We could call ocfs2_insert_at_leaf() for some types
         * of splits, but it's easier to just let one separate
         * function sort it all out.
         */
        ocfs2_split_record(et, left_path, right_path,
                   insert_rec, insert->ins_split);

        /*
         * Split might have modified either leaf and we don't
         * have a guarantee that the later edge insert will
         * dirty this for us.
         */
        if (left_path)
            ocfs2_journal_dirty(handle,
                        path_leaf_bh(left_path));
    } else
        ocfs2_insert_at_leaf(et, insert_rec, path_leaf_el(right_path),
                     insert);

    ocfs2_journal_dirty(handle, leaf_bh);

    if (left_path) {
        /*
         * The rotate code has indicated that we need to fix
         * up portions of the tree after the insert.
         *
         * XXX: Should we extend the transaction here?
         */
        subtree_index = ocfs2_find_subtree_root(et, left_path,
                            right_path);
        ocfs2_complete_edge_insert(handle, left_path, right_path,
                       subtree_index);
    }

    ret = 0;
out:
    return ret;
}

static int ocfs2_do_insert_extent(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_extent_rec *insert_rec,
                  struct ocfs2_insert_type *type)
{
    int ret, rotate = 0;
    u32 cpos;
    struct ocfs2_path *right_path = NULL;
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_extent_list *el;

    el = et->et_root_el;

    ret = ocfs2_et_root_journal_access(handle, et,
                       OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (le16_to_cpu(el->l_tree_depth) == 0) {
        ocfs2_insert_at_leaf(et, insert_rec, el, type);
        goto out_update_clusters;
    }

    right_path = ocfs2_new_path_from_et(et);
    if (!right_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    /*
     * Determine the path to start with. Rotations need the
     * rightmost path, everything else can go directly to the
     * target leaf.
     */
    cpos = le32_to_cpu(insert_rec->e_cpos);
    if (type->ins_appending == APPEND_NONE &&
        type->ins_contig == CONTIG_NONE) {
        rotate = 1;
        cpos = UINT_MAX;
    }

    ret = ocfs2_find_path(et->et_ci, right_path, cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * Rotations and appends need special treatment - they modify
     * parts of the tree's above them.
     *
     * Both might pass back a path immediate to the left of the
     * one being inserted to. This will be cause
     * ocfs2_insert_path() to modify the rightmost records of
     * left_path to account for an edge insert.
     *
     * XXX: When modifying this code, keep in mind that an insert
     * can wind up skipping both of these two special cases...
     */
    if (rotate) {
        ret = ocfs2_rotate_tree_right(handle, et, type->ins_split,
                          le32_to_cpu(insert_rec->e_cpos),
                          right_path, &left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * ocfs2_rotate_tree_right() might have extended the
         * transaction without re-journaling our tree root.
         */
        ret = ocfs2_et_root_journal_access(handle, et,
                           OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    } else if (type->ins_appending == APPEND_TAIL
           && type->ins_contig != CONTIG_LEFT) {
        ret = ocfs2_append_rec_to_path(handle, et, insert_rec,
                           right_path, &left_path);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    ret = ocfs2_insert_path(handle, et, left_path, right_path,
                insert_rec, type);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

out_update_clusters:
    if (type->ins_split == SPLIT_NONE)
        ocfs2_et_update_clusters(et,
                     le16_to_cpu(insert_rec->e_leaf_clusters));

    ocfs2_journal_dirty(handle, et->et_root_bh);

out:
    ocfs2_free_path(left_path);
    ocfs2_free_path(right_path);

    return ret;
}

static enum ocfs2_contig_type
ocfs2_figure_merge_contig_type(struct ocfs2_extent_tree *et,
                   struct ocfs2_path *path,
                   struct ocfs2_extent_list *el, int index,
                   struct ocfs2_extent_rec *split_rec)
{
    int status;
    enum ocfs2_contig_type ret = CONTIG_NONE;
    u32 left_cpos, right_cpos;
    struct ocfs2_extent_rec *rec = NULL;
    struct ocfs2_extent_list *new_el;
    struct ocfs2_path *left_path = NULL, *right_path = NULL;
    struct buffer_head *bh;
    struct ocfs2_extent_block *eb;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);

    if (index > 0) {
        rec = &el->l_recs[index - 1];
    } else if (path->p_tree_depth > 0) {
        status = ocfs2_find_cpos_for_left_leaf(sb, path, &left_cpos);
        if (status)
            goto out;

        if (left_cpos != 0) {
            left_path = ocfs2_new_path_from_path(path);
            if (!left_path)
                goto out;

            status = ocfs2_find_path(et->et_ci, left_path,
                         left_cpos);
            if (status)
                goto out;

            new_el = path_leaf_el(left_path);

            if (le16_to_cpu(new_el->l_next_free_rec) !=
                le16_to_cpu(new_el->l_count)) {
                bh = path_leaf_bh(left_path);
                eb = (struct ocfs2_extent_block *)bh->b_data;
                ocfs2_error(sb,
                        "Extent block #%llu has an "
                        "invalid l_next_free_rec of "
                        "%d.  It should have "
                        "matched the l_count of %d",
                        (unsigned long long)le64_to_cpu(eb->h_blkno),
                        le16_to_cpu(new_el->l_next_free_rec),
                        le16_to_cpu(new_el->l_count));
                status = -EINVAL;
                goto out;
            }
            rec = &new_el->l_recs[
                le16_to_cpu(new_el->l_next_free_rec) - 1];
        }
    }

    /*
     * We're careful to check for an empty extent record here -
     * the merge code will know what to do if it sees one.
     */
    if (rec) {
        if (index == 1 && ocfs2_is_empty_extent(rec)) {
            if (split_rec->e_cpos == el->l_recs[index].e_cpos)
                ret = CONTIG_RIGHT;
        } else {
            ret = ocfs2_et_extent_contig(et, rec, split_rec);
        }
    }

    rec = NULL;
    if (index < (le16_to_cpu(el->l_next_free_rec) - 1))
        rec = &el->l_recs[index + 1];
    else if (le16_to_cpu(el->l_next_free_rec) == le16_to_cpu(el->l_count) &&
         path->p_tree_depth > 0) {
        status = ocfs2_find_cpos_for_right_leaf(sb, path, &right_cpos);
        if (status)
            goto out;

        if (right_cpos == 0)
            goto out;

        right_path = ocfs2_new_path_from_path(path);
        if (!right_path)
            goto out;

        status = ocfs2_find_path(et->et_ci, right_path, right_cpos);
        if (status)
            goto out;

        new_el = path_leaf_el(right_path);
        rec = &new_el->l_recs[0];
        if (ocfs2_is_empty_extent(rec)) {
            if (le16_to_cpu(new_el->l_next_free_rec) <= 1) {
                bh = path_leaf_bh(right_path);
                eb = (struct ocfs2_extent_block *)bh->b_data;
                ocfs2_error(sb,
                        "Extent block #%llu has an "
                        "invalid l_next_free_rec of %d",
                        (unsigned long long)le64_to_cpu(eb->h_blkno),
                        le16_to_cpu(new_el->l_next_free_rec));
                status = -EINVAL;
                goto out;
            }
            rec = &new_el->l_recs[1];
        }
    }

    if (rec) {
        enum ocfs2_contig_type contig_type;

        contig_type = ocfs2_et_extent_contig(et, rec, split_rec);

        if (contig_type == CONTIG_LEFT && ret == CONTIG_RIGHT)
            ret = CONTIG_LEFTRIGHT;
        else if (ret == CONTIG_NONE)
            ret = contig_type;
    }

out:
    if (left_path)
        ocfs2_free_path(left_path);
    if (right_path)
        ocfs2_free_path(right_path);

    return ret;
}

static void ocfs2_figure_contig_type(struct ocfs2_extent_tree *et,
                     struct ocfs2_insert_type *insert,
                     struct ocfs2_extent_list *el,
                     struct ocfs2_extent_rec *insert_rec)
{
    int i;
    enum ocfs2_contig_type contig_type = CONTIG_NONE;

    BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

    for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
        contig_type = ocfs2_et_extent_contig(et, &el->l_recs[i],
                             insert_rec);
        if (contig_type != CONTIG_NONE) {
            insert->ins_contig_index = i;
            break;
        }
    }
    insert->ins_contig = contig_type;

    if (insert->ins_contig != CONTIG_NONE) {
        struct ocfs2_extent_rec *rec =
                &el->l_recs[insert->ins_contig_index];
        unsigned int len = le16_to_cpu(rec->e_leaf_clusters) +
                   le16_to_cpu(insert_rec->e_leaf_clusters);

        /*
         * Caller might want us to limit the size of extents, don't
         * calculate contiguousness if we might exceed that limit.
         */
        if (et->et_max_leaf_clusters &&
            (len > et->et_max_leaf_clusters))
            insert->ins_contig = CONTIG_NONE;
    }
}

/*
 * This should only be called against the righmost leaf extent list.
 *
 * ocfs2_figure_appending_type() will figure out whether we'll have to
 * insert at the tail of the rightmost leaf.
 *
 * This should also work against the root extent list for tree's with 0
 * depth. If we consider the root extent list to be the rightmost leaf node
 * then the logic here makes sense.
 */
static void ocfs2_figure_appending_type(struct ocfs2_insert_type *insert,
                    struct ocfs2_extent_list *el,
                    struct ocfs2_extent_rec *insert_rec)
{
    int i;
    u32 cpos = le32_to_cpu(insert_rec->e_cpos);
    struct ocfs2_extent_rec *rec;

    insert->ins_appending = APPEND_NONE;

    BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

    if (!el->l_next_free_rec)
        goto set_tail_append;

    if (ocfs2_is_empty_extent(&el->l_recs[0])) {
        /* Were all records empty? */
        if (le16_to_cpu(el->l_next_free_rec) == 1)
            goto set_tail_append;
    }

    i = le16_to_cpu(el->l_next_free_rec) - 1;
    rec = &el->l_recs[i];

    if (cpos >=
        (le32_to_cpu(rec->e_cpos) + le16_to_cpu(rec->e_leaf_clusters)))
        goto set_tail_append;

    return;

set_tail_append:
    insert->ins_appending = APPEND_TAIL;
}

/*
 * Helper function called at the beginning of an insert.
 *
 * This computes a few things that are commonly used in the process of
 * inserting into the btree:
 *   - Whether the new extent is contiguous with an existing one.
 *   - The current tree depth.
 *   - Whether the insert is an appending one.
 *   - The total # of free records in the tree.
 *
 * All of the information is stored on the ocfs2_insert_type
 * structure.
 */
static int ocfs2_figure_insert_type(struct ocfs2_extent_tree *et,
                    struct buffer_head **last_eb_bh,
                    struct ocfs2_extent_rec *insert_rec,
                    int *free_records,
                    struct ocfs2_insert_type *insert)
{
    int ret;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *el;
    struct ocfs2_path *path = NULL;
    struct buffer_head *bh = NULL;

    insert->ins_split = SPLIT_NONE;

    el = et->et_root_el;
    insert->ins_tree_depth = le16_to_cpu(el->l_tree_depth);

    if (el->l_tree_depth) {
        /*
         * If we have tree depth, we read in the
         * rightmost extent block ahead of time as
         * ocfs2_figure_insert_type() and ocfs2_add_branch()
         * may want it later.
         */
        ret = ocfs2_read_extent_block(et->et_ci,
                          ocfs2_et_get_last_eb_blk(et),
                          &bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
        eb = (struct ocfs2_extent_block *) bh->b_data;
        el = &eb->h_list;
    }

    /*
     * Unless we have a contiguous insert, we'll need to know if
     * there is room left in our allocation tree for another
     * extent record.
     *
     * XXX: This test is simplistic, we can search for empty
     * extent records too.
     */
    *free_records = le16_to_cpu(el->l_count) -
        le16_to_cpu(el->l_next_free_rec);

    if (!insert->ins_tree_depth) {
        ocfs2_figure_contig_type(et, insert, el, insert_rec);
        ocfs2_figure_appending_type(insert, el, insert_rec);
        return 0;
    }

    path = ocfs2_new_path_from_et(et);
    if (!path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    /*
     * In the case that we're inserting past what the tree
     * currently accounts for, ocfs2_find_path() will return for
     * us the rightmost tree path. This is accounted for below in
     * the appending code.
     */
    ret = ocfs2_find_path(et->et_ci, path, le32_to_cpu(insert_rec->e_cpos));
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    el = path_leaf_el(path);

    /*
     * Now that we have the path, there's two things we want to determine:
     * 1) Contiguousness (also set contig_index if this is so)
     *
     * 2) Are we doing an append? We can trivially break this up
         *     into two types of appends: simple record append, or a
         *     rotate inside the tail leaf.
     */
    ocfs2_figure_contig_type(et, insert, el, insert_rec);

    /*
     * The insert code isn't quite ready to deal with all cases of
     * left contiguousness. Specifically, if it's an insert into
     * the 1st record in a leaf, it will require the adjustment of
     * cluster count on the last record of the path directly to it's
     * left. For now, just catch that case and fool the layers
     * above us. This works just fine for tree_depth == 0, which
     * is why we allow that above.
     */
    if (insert->ins_contig == CONTIG_LEFT &&
        insert->ins_contig_index == 0)
        insert->ins_contig = CONTIG_NONE;

    /*
     * Ok, so we can simply compare against last_eb to figure out
     * whether the path doesn't exist. This will only happen in
     * the case that we're doing a tail append, so maybe we can
     * take advantage of that information somehow.
     */
    if (ocfs2_et_get_last_eb_blk(et) ==
        path_leaf_bh(path)->b_blocknr) {
        /*
         * Ok, ocfs2_find_path() returned us the rightmost
         * tree path. This might be an appending insert. There are
         * two cases:
         *    1) We're doing a true append at the tail:
         *  -This might even be off the end of the leaf
         *    2) We're "appending" by rotating in the tail
         */
        ocfs2_figure_appending_type(insert, el, insert_rec);
    }

out:
    ocfs2_free_path(path);

    if (ret == 0)
        *last_eb_bh = bh;
    else
        brelse(bh);
    return ret;
}

/*
 * Insert an extent into a btree.
 *
 * The caller needs to update the owning btree's cluster count.
 */
int ocfs2_insert_extent(handle_t *handle,
            struct ocfs2_extent_tree *et,
            u32 cpos,
            u64 start_blk,
            u32 new_clusters,
            u8 flags,
            struct ocfs2_alloc_context *meta_ac)
{
    int status;
    int uninitialized_var(free_records);
    struct buffer_head *last_eb_bh = NULL;
    struct ocfs2_insert_type insert = {0, };
    struct ocfs2_extent_rec rec;

    trace_ocfs2_insert_extent_start(
        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
        cpos, new_clusters);

    memset(&rec, 0, sizeof(rec));
    rec.e_cpos = cpu_to_le32(cpos);
    rec.e_blkno = cpu_to_le64(start_blk);
    rec.e_leaf_clusters = cpu_to_le16(new_clusters);
    rec.e_flags = flags;
    status = ocfs2_et_insert_check(et, &rec);
    if (status) {
        mlog_errno(status);
        goto bail;
    }

    status = ocfs2_figure_insert_type(et, &last_eb_bh, &rec,
                      &free_records, &insert);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    trace_ocfs2_insert_extent(insert.ins_appending, insert.ins_contig,
                  insert.ins_contig_index, free_records,
                  insert.ins_tree_depth);

    if (insert.ins_contig == CONTIG_NONE && free_records == 0) {
        status = ocfs2_grow_tree(handle, et,
                     &insert.ins_tree_depth, &last_eb_bh,
                     meta_ac);
        if (status) {
            mlog_errno(status);
            goto bail;
        }
    }

    /* Finally, we can add clusters. This might rotate the tree for us. */
    status = ocfs2_do_insert_extent(handle, et, &rec, &insert);
    if (status < 0)
        mlog_errno(status);
    else
        ocfs2_et_extent_map_insert(et, &rec);

bail:
    brelse(last_eb_bh);

    return status;
}

/*
 * Allcate and add clusters into the extent b-tree.
 * The new clusters(clusters_to_add) will be inserted at logical_offset.
 * The extent b-tree's root is specified by et, and
 * it is not limited to the file storage. Any extent tree can use this
 * function if it implements the proper ocfs2_extent_tree.
 */
int ocfs2_add_clusters_in_btree(handle_t *handle,
                struct ocfs2_extent_tree *et,
                u32 *logical_offset,
                u32 clusters_to_add,
                int mark_unwritten,
                struct ocfs2_alloc_context *data_ac,
                struct ocfs2_alloc_context *meta_ac,
                enum ocfs2_alloc_restarted *reason_ret)
{
    int status = 0, err = 0;
    int free_extents;
    enum ocfs2_alloc_restarted reason = RESTART_NONE;
    u32 bit_off, num_bits;
    u64 block;
    u8 flags = 0;
    struct ocfs2_super *osb =
        OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));

    BUG_ON(!clusters_to_add);

    if (mark_unwritten)
        flags = OCFS2_EXT_UNWRITTEN;

    free_extents = ocfs2_num_free_extents(osb, et);
    if (free_extents < 0) {
        status = free_extents;
        mlog_errno(status);
        goto leave;
    }

    /* there are two cases which could cause us to EAGAIN in the
     * we-need-more-metadata case:
     * 1) we haven't reserved *any*
     * 2) we are so fragmented, we've needed to add metadata too
     *    many times. */
    if (!free_extents && !meta_ac) {
        err = -1;
        status = -EAGAIN;
        reason = RESTART_META;
        goto leave;
    } else if ((!free_extents)
           && (ocfs2_alloc_context_bits_left(meta_ac)
               < ocfs2_extend_meta_needed(et->et_root_el))) {
        err = -2;
        status = -EAGAIN;
        reason = RESTART_META;
        goto leave;
    }

    status = __ocfs2_claim_clusters(handle, data_ac, 1,
                    clusters_to_add, &bit_off, &num_bits);
    if (status < 0) {
        if (status != -ENOSPC)
            mlog_errno(status);
        goto leave;
    }

    BUG_ON(num_bits > clusters_to_add);

    /* reserve our write early -- insert_extent may update the tree root */
    status = ocfs2_et_root_journal_access(handle, et,
                          OCFS2_JOURNAL_ACCESS_WRITE);
    if (status < 0) {
        mlog_errno(status);
        goto leave;
    }

    block = ocfs2_clusters_to_blocks(osb->sb, bit_off);
    trace_ocfs2_add_clusters_in_btree(
         (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
         bit_off, num_bits);
    status = ocfs2_insert_extent(handle, et, *logical_offset, block,
                     num_bits, flags, meta_ac);
    if (status < 0) {
        mlog_errno(status);
        goto leave;
    }

    ocfs2_journal_dirty(handle, et->et_root_bh);

    clusters_to_add -= num_bits;
    *logical_offset += num_bits;

    if (clusters_to_add) {
        err = clusters_to_add;
        status = -EAGAIN;
        reason = RESTART_TRANS;
    }

leave:
    if (reason_ret)
        *reason_ret = reason;
    trace_ocfs2_add_clusters_in_btree_ret(status, reason, err);
    return status;
}

static void ocfs2_make_right_split_rec(struct super_block *sb,
                       struct ocfs2_extent_rec *split_rec,
                       u32 cpos,
                       struct ocfs2_extent_rec *rec)
{
    u32 rec_cpos = le32_to_cpu(rec->e_cpos);
    u32 rec_range = rec_cpos + le16_to_cpu(rec->e_leaf_clusters);

    memset(split_rec, 0, sizeof(struct ocfs2_extent_rec));

    split_rec->e_cpos = cpu_to_le32(cpos);
    split_rec->e_leaf_clusters = cpu_to_le16(rec_range - cpos);

    split_rec->e_blkno = rec->e_blkno;
    le64_add_cpu(&split_rec->e_blkno,
             ocfs2_clusters_to_blocks(sb, cpos - rec_cpos));

    split_rec->e_flags = rec->e_flags;
}

static int ocfs2_split_and_insert(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_path *path,
                  struct buffer_head **last_eb_bh,
                  int split_index,
                  struct ocfs2_extent_rec *orig_split_rec,
                  struct ocfs2_alloc_context *meta_ac)
{
    int ret = 0, depth;
    unsigned int insert_range, rec_range, do_leftright = 0;
    struct ocfs2_extent_rec tmprec;
    struct ocfs2_extent_list *rightmost_el;
    struct ocfs2_extent_rec rec;
    struct ocfs2_extent_rec split_rec = *orig_split_rec;
    struct ocfs2_insert_type insert;
    struct ocfs2_extent_block *eb;

leftright:
    /*
     * Store a copy of the record on the stack - it might move
     * around as the tree is manipulated below.
     */
    rec = path_leaf_el(path)->l_recs[split_index];

    rightmost_el = et->et_root_el;

    depth = le16_to_cpu(rightmost_el->l_tree_depth);
    if (depth) {
        BUG_ON(!(*last_eb_bh));
        eb = (struct ocfs2_extent_block *) (*last_eb_bh)->b_data;
        rightmost_el = &eb->h_list;
    }

    if (le16_to_cpu(rightmost_el->l_next_free_rec) ==
        le16_to_cpu(rightmost_el->l_count)) {
        ret = ocfs2_grow_tree(handle, et,
                      &depth, last_eb_bh, meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    memset(&insert, 0, sizeof(struct ocfs2_insert_type));
    insert.ins_appending = APPEND_NONE;
    insert.ins_contig = CONTIG_NONE;
    insert.ins_tree_depth = depth;

    insert_range = le32_to_cpu(split_rec.e_cpos) +
        le16_to_cpu(split_rec.e_leaf_clusters);
    rec_range = le32_to_cpu(rec.e_cpos) +
        le16_to_cpu(rec.e_leaf_clusters);

    if (split_rec.e_cpos == rec.e_cpos) {
        insert.ins_split = SPLIT_LEFT;
    } else if (insert_range == rec_range) {
        insert.ins_split = SPLIT_RIGHT;
    } else {
        /*
         * Left/right split. We fake this as a right split
         * first and then make a second pass as a left split.
         */
        insert.ins_split = SPLIT_RIGHT;

        ocfs2_make_right_split_rec(ocfs2_metadata_cache_get_super(et->et_ci),
                       &tmprec, insert_range, &rec);

        split_rec = tmprec;

        BUG_ON(do_leftright);
        do_leftright = 1;
    }

    ret = ocfs2_do_insert_extent(handle, et, &split_rec, &insert);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (do_leftright == 1) {
        u32 cpos;
        struct ocfs2_extent_list *el;

        do_leftright++;
        split_rec = *orig_split_rec;

        ocfs2_reinit_path(path, 1);

        cpos = le32_to_cpu(split_rec.e_cpos);
        ret = ocfs2_find_path(et->et_ci, path, cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        el = path_leaf_el(path);
        split_index = ocfs2_search_extent_list(el, cpos);
        goto leftright;
    }
out:

    return ret;
}

static int ocfs2_replace_extent_rec(handle_t *handle,
                    struct ocfs2_extent_tree *et,
                    struct ocfs2_path *path,
                    struct ocfs2_extent_list *el,
                    int split_index,
                    struct ocfs2_extent_rec *split_rec)
{
    int ret;

    ret = ocfs2_path_bh_journal_access(handle, et->et_ci, path,
                       path_num_items(path) - 1);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    el->l_recs[split_index] = *split_rec;

    ocfs2_journal_dirty(handle, path_leaf_bh(path));
out:
    return ret;
}

/*
 * Split part or all of the extent record at split_index in the leaf
 * pointed to by path. Merge with the contiguous extent record if needed.
 *
 * Care is taken to handle contiguousness so as to not grow the tree.
 *
 * meta_ac is not strictly necessary - we only truly need it if growth
 * of the tree is required. All other cases will degrade into a less
 * optimal tree layout.
 *
 * last_eb_bh should be the rightmost leaf block for any extent
 * btree. Since a split may grow the tree or a merge might shrink it,
 * the caller cannot trust the contents of that buffer after this call.
 *
 * This code is optimized for readability - several passes might be
 * made over certain portions of the tree. All of those blocks will
 * have been brought into cache (and pinned via the journal), so the
 * extra overhead is not expressed in terms of disk reads.
 */
int ocfs2_split_extent(handle_t *handle,
               struct ocfs2_extent_tree *et,
               struct ocfs2_path *path,
               int split_index,
               struct ocfs2_extent_rec *split_rec,
               struct ocfs2_alloc_context *meta_ac,
               struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret = 0;
    struct ocfs2_extent_list *el = path_leaf_el(path);
    struct buffer_head *last_eb_bh = NULL;
    struct ocfs2_extent_rec *rec = &el->l_recs[split_index];
    struct ocfs2_merge_ctxt ctxt;
    struct ocfs2_extent_list *rightmost_el;

    if (le32_to_cpu(rec->e_cpos) > le32_to_cpu(split_rec->e_cpos) ||
        ((le32_to_cpu(rec->e_cpos) + le16_to_cpu(rec->e_leaf_clusters)) <
         (le32_to_cpu(split_rec->e_cpos) + le16_to_cpu(split_rec->e_leaf_clusters)))) {
        ret = -EIO;
        mlog_errno(ret);
        goto out;
    }

    ctxt.c_contig_type = ocfs2_figure_merge_contig_type(et, path, el,
                                split_index,
                                split_rec);

    /*
     * The core merge / split code wants to know how much room is
     * left in this allocation tree, so we pass the
     * rightmost extent list.
     */
    if (path->p_tree_depth) {
        struct ocfs2_extent_block *eb;

        ret = ocfs2_read_extent_block(et->et_ci,
                          ocfs2_et_get_last_eb_blk(et),
                          &last_eb_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
        rightmost_el = &eb->h_list;
    } else
        rightmost_el = path_root_el(path);

    if (rec->e_cpos == split_rec->e_cpos &&
        rec->e_leaf_clusters == split_rec->e_leaf_clusters)
        ctxt.c_split_covers_rec = 1;
    else
        ctxt.c_split_covers_rec = 0;

    ctxt.c_has_empty_extent = ocfs2_is_empty_extent(&el->l_recs[0]);

    trace_ocfs2_split_extent(split_index, ctxt.c_contig_type,
                 ctxt.c_has_empty_extent,
                 ctxt.c_split_covers_rec);

    if (ctxt.c_contig_type == CONTIG_NONE) {
        if (ctxt.c_split_covers_rec)
            ret = ocfs2_replace_extent_rec(handle, et, path, el,
                               split_index, split_rec);
        else
            ret = ocfs2_split_and_insert(handle, et, path,
                             &last_eb_bh, split_index,
                             split_rec, meta_ac);
        if (ret)
            mlog_errno(ret);
    } else {
        ret = ocfs2_try_to_merge_extent(handle, et, path,
                        split_index, split_rec,
                        dealloc, &ctxt);
        if (ret)
            mlog_errno(ret);
    }

out:
    brelse(last_eb_bh);
    return ret;
}

/*
 * Change the flags of the already-existing extent at cpos for len clusters.
 *
 * new_flags: the flags we want to set.
 * clear_flags: the flags we want to clear.
 * phys: the new physical offset we want this new extent starts from.
 *
 * If the existing extent is larger than the request, initiate a
 * split. An attempt will be made at merging with adjacent extents.
 *
 * The caller is responsible for passing down meta_ac if we'll need it.
 */
int ocfs2_change_extent_flag(handle_t *handle,
                 struct ocfs2_extent_tree *et,
                 u32 cpos, u32 len, u32 phys,
                 struct ocfs2_alloc_context *meta_ac,
                 struct ocfs2_cached_dealloc_ctxt *dealloc,
                 int new_flags, int clear_flags)
{
    int ret, index;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
    u64 start_blkno = ocfs2_clusters_to_blocks(sb, phys);
    struct ocfs2_extent_rec split_rec;
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec;

    left_path = ocfs2_new_path_from_et(et);
    if (!left_path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_path(et->et_ci, left_path, cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }
    el = path_leaf_el(left_path);

    index = ocfs2_search_extent_list(el, cpos);
    if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
        ocfs2_error(sb,
                "Owner %llu has an extent at cpos %u which can no "
                "longer be found.\n",
                 (unsigned long long)
                 ocfs2_metadata_cache_owner(et->et_ci), cpos);
        ret = -EROFS;
        goto out;
    }

    ret = -EIO;
    rec = &el->l_recs[index];
    if (new_flags && (rec->e_flags & new_flags)) {
        mlog(ML_ERROR, "Owner %llu tried to set %d flags on an "
             "extent that already had them",
             (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
             new_flags);
        goto out;
    }

    if (clear_flags && !(rec->e_flags & clear_flags)) {
        mlog(ML_ERROR, "Owner %llu tried to clear %d flags on an "
             "extent that didn't have them",
             (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
             clear_flags);
        goto out;
    }

    memset(&split_rec, 0, sizeof(struct ocfs2_extent_rec));
    split_rec.e_cpos = cpu_to_le32(cpos);
    split_rec.e_leaf_clusters = cpu_to_le16(len);
    split_rec.e_blkno = cpu_to_le64(start_blkno);
    split_rec.e_flags = rec->e_flags;
    if (new_flags)
        split_rec.e_flags |= new_flags;
    if (clear_flags)
        split_rec.e_flags &= ~clear_flags;

    ret = ocfs2_split_extent(handle, et, left_path,
                 index, &split_rec, meta_ac,
                 dealloc);
    if (ret)
        mlog_errno(ret);

out:
    ocfs2_free_path(left_path);
    return ret;

}

/*
 * Mark the already-existing extent at cpos as written for len clusters.
 * This removes the unwritten extent flag.
 *
 * If the existing extent is larger than the request, initiate a
 * split. An attempt will be made at merging with adjacent extents.
 *
 * The caller is responsible for passing down meta_ac if we'll need it.
 */
int ocfs2_mark_extent_written(struct inode *inode,
                  struct ocfs2_extent_tree *et,
                  handle_t *handle, u32 cpos, u32 len, u32 phys,
                  struct ocfs2_alloc_context *meta_ac,
                  struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret;

    trace_ocfs2_mark_extent_written(
        (unsigned long long)OCFS2_I(inode)->ip_blkno,
        cpos, len, phys);

    if (!ocfs2_writes_unwritten_extents(OCFS2_SB(inode->i_sb))) {
        ocfs2_error(inode->i_sb, "Inode %llu has unwritten extents "
                "that are being written to, but the feature bit "
                "is not set in the super block.",
                (unsigned long long)OCFS2_I(inode)->ip_blkno);
        ret = -EROFS;
        goto out;
    }

    /*
     * XXX: This should be fixed up so that we just re-insert the
     * next extent records.
     */
    ocfs2_et_extent_map_truncate(et, 0);

    ret = ocfs2_change_extent_flag(handle, et, cpos,
                       len, phys, meta_ac, dealloc,
                       0, OCFS2_EXT_UNWRITTEN);
    if (ret)
        mlog_errno(ret);

out:
    return ret;
}

static int ocfs2_split_tree(handle_t *handle, struct ocfs2_extent_tree *et,
                struct ocfs2_path *path,
                int index, u32 new_range,
                struct ocfs2_alloc_context *meta_ac)
{
    int ret, depth, credits;
    struct buffer_head *last_eb_bh = NULL;
    struct ocfs2_extent_block *eb;
    struct ocfs2_extent_list *rightmost_el, *el;
    struct ocfs2_extent_rec split_rec;
    struct ocfs2_extent_rec *rec;
    struct ocfs2_insert_type insert;

    /*
     * Setup the record to split before we grow the tree.
     */
    el = path_leaf_el(path);
    rec = &el->l_recs[index];
    ocfs2_make_right_split_rec(ocfs2_metadata_cache_get_super(et->et_ci),
                   &split_rec, new_range, rec);

    depth = path->p_tree_depth;
    if (depth > 0) {
        ret = ocfs2_read_extent_block(et->et_ci,
                          ocfs2_et_get_last_eb_blk(et),
                          &last_eb_bh);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }

        eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
        rightmost_el = &eb->h_list;
    } else
        rightmost_el = path_leaf_el(path);

    credits = path->p_tree_depth +
          ocfs2_extend_meta_needed(et->et_root_el);
    ret = ocfs2_extend_trans(handle, credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (le16_to_cpu(rightmost_el->l_next_free_rec) ==
        le16_to_cpu(rightmost_el->l_count)) {
        ret = ocfs2_grow_tree(handle, et, &depth, &last_eb_bh,
                      meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    memset(&insert, 0, sizeof(struct ocfs2_insert_type));
    insert.ins_appending = APPEND_NONE;
    insert.ins_contig = CONTIG_NONE;
    insert.ins_split = SPLIT_RIGHT;
    insert.ins_tree_depth = depth;

    ret = ocfs2_do_insert_extent(handle, et, &split_rec, &insert);
    if (ret)
        mlog_errno(ret);

out:
    brelse(last_eb_bh);
    return ret;
}

static int ocfs2_truncate_rec(handle_t *handle,
                  struct ocfs2_extent_tree *et,
                  struct ocfs2_path *path, int index,
                  struct ocfs2_cached_dealloc_ctxt *dealloc,
                  u32 cpos, u32 len)
{
    int ret;
    u32 left_cpos, rec_range, trunc_range;
    int wants_rotate = 0, is_rightmost_tree_rec = 0;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
    struct ocfs2_path *left_path = NULL;
    struct ocfs2_extent_list *el = path_leaf_el(path);
    struct ocfs2_extent_rec *rec;
    struct ocfs2_extent_block *eb;

    if (ocfs2_is_empty_extent(&el->l_recs[0]) && index > 0) {
        ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        index--;
    }

    if (index == (le16_to_cpu(el->l_next_free_rec) - 1) &&
        path->p_tree_depth) {
        /*
         * Check whether this is the rightmost tree record. If
         * we remove all of this record or part of its right
         * edge then an update of the record lengths above it
         * will be required.
         */
        eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
        if (eb->h_next_leaf_blk == 0)
            is_rightmost_tree_rec = 1;
    }

    rec = &el->l_recs[index];
    if (index == 0 && path->p_tree_depth &&
        le32_to_cpu(rec->e_cpos) == cpos) {
        /*
         * Changing the leftmost offset (via partial or whole
         * record truncate) of an interior (or rightmost) path
         * means we have to update the subtree that is formed
         * by this leaf and the one to it's left.
         *
         * There are two cases we can skip:
         *   1) Path is the leftmost one in our btree.
         *   2) The leaf is rightmost and will be empty after
         *      we remove the extent record - the rotate code
         *      knows how to update the newly formed edge.
         */

        ret = ocfs2_find_cpos_for_left_leaf(sb, path, &left_cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (left_cpos && le16_to_cpu(el->l_next_free_rec) > 1) {
            left_path = ocfs2_new_path_from_path(path);
            if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
            }

            ret = ocfs2_find_path(et->et_ci, left_path,
                          left_cpos);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }
    }

    ret = ocfs2_extend_rotate_transaction(handle, 0,
                          handle->h_buffer_credits,
                          path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_path(et->et_ci, handle, path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_path(et->et_ci, handle, left_path);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
    trunc_range = cpos + len;

    if (le32_to_cpu(rec->e_cpos) == cpos && rec_range == trunc_range) {
        int next_free;

        memset(rec, 0, sizeof(*rec));
        ocfs2_cleanup_merge(el, index);
        wants_rotate = 1;

        next_free = le16_to_cpu(el->l_next_free_rec);
        if (is_rightmost_tree_rec && next_free > 1) {
            /*
             * We skip the edge update if this path will
             * be deleted by the rotate code.
             */
            rec = &el->l_recs[next_free - 1];
            ocfs2_adjust_rightmost_records(handle, et, path,
                               rec);
        }
    } else if (le32_to_cpu(rec->e_cpos) == cpos) {
        /* Remove leftmost portion of the record. */
        le32_add_cpu(&rec->e_cpos, len);
        le64_add_cpu(&rec->e_blkno, ocfs2_clusters_to_blocks(sb, len));
        le16_add_cpu(&rec->e_leaf_clusters, -len);
    } else if (rec_range == trunc_range) {
        /* Remove rightmost portion of the record */
        le16_add_cpu(&rec->e_leaf_clusters, -len);
        if (is_rightmost_tree_rec)
            ocfs2_adjust_rightmost_records(handle, et, path, rec);
    } else {
        /* Caller should have trapped this. */
        mlog(ML_ERROR, "Owner %llu: Invalid record truncate: (%u, %u) "
             "(%u, %u)\n",
             (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
             le32_to_cpu(rec->e_cpos),
             le16_to_cpu(rec->e_leaf_clusters), cpos, len);
        BUG();
    }

    if (left_path) {
        int subtree_index;

        subtree_index = ocfs2_find_subtree_root(et, left_path, path);
        ocfs2_complete_edge_insert(handle, left_path, path,
                       subtree_index);
    }

    ocfs2_journal_dirty(handle, path_leaf_bh(path));

    ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

out:
    ocfs2_free_path(left_path);
    return ret;
}

int ocfs2_remove_extent(handle_t *handle,
            struct ocfs2_extent_tree *et,
            u32 cpos, u32 len,
            struct ocfs2_alloc_context *meta_ac,
            struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret, index;
    u32 rec_range, trunc_range;
    struct ocfs2_extent_rec *rec;
    struct ocfs2_extent_list *el;
    struct ocfs2_path *path = NULL;

    /*
     * XXX: Why are we truncating to 0 instead of wherever this
     * affects us?
     */
    ocfs2_et_extent_map_truncate(et, 0);

    path = ocfs2_new_path_from_et(et);
    if (!path) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_find_path(et->et_ci, path, cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    el = path_leaf_el(path);
    index = ocfs2_search_extent_list(el, cpos);
    if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                "Owner %llu has an extent at cpos %u which can no "
                "longer be found.\n",
                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                cpos);
        ret = -EROFS;
        goto out;
    }

    /*
     * We have 3 cases of extent removal:
     *   1) Range covers the entire extent rec
     *   2) Range begins or ends on one edge of the extent rec
     *   3) Range is in the middle of the extent rec (no shared edges)
     *
     * For case 1 we remove the extent rec and left rotate to
     * fill the hole.
     *
     * For case 2 we just shrink the existing extent rec, with a
     * tree update if the shrinking edge is also the edge of an
     * extent block.
     *
     * For case 3 we do a right split to turn the extent rec into
     * something case 2 can handle.
     */
    rec = &el->l_recs[index];
    rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
    trunc_range = cpos + len;

    BUG_ON(cpos < le32_to_cpu(rec->e_cpos) || trunc_range > rec_range);

    trace_ocfs2_remove_extent(
        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
        cpos, len, index, le32_to_cpu(rec->e_cpos),
        ocfs2_rec_clusters(el, rec));

    if (le32_to_cpu(rec->e_cpos) == cpos || rec_range == trunc_range) {
        ret = ocfs2_truncate_rec(handle, et, path, index, dealloc,
                     cpos, len);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    } else {
        ret = ocfs2_split_tree(handle, et, path, index,
                       trunc_range, meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * The split could have manipulated the tree enough to
         * move the record location, so we have to look for it again.
         */
        ocfs2_reinit_path(path, 1);

        ret = ocfs2_find_path(et->et_ci, path, cpos);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        el = path_leaf_el(path);
        index = ocfs2_search_extent_list(el, cpos);
        if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu: split at cpos %u lost record.",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                    cpos);
            ret = -EROFS;
            goto out;
        }

        /*
         * Double check our values here. If anything is fishy,
         * it's easier to catch it at the top level.
         */
        rec = &el->l_recs[index];
        rec_range = le32_to_cpu(rec->e_cpos) +
            ocfs2_rec_clusters(el, rec);
        if (rec_range != trunc_range) {
            ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                    "Owner %llu: error after split at cpos %u"
                    "trunc len %u, existing record is (%u,%u)",
                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                    cpos, len, le32_to_cpu(rec->e_cpos),
                    ocfs2_rec_clusters(el, rec));
            ret = -EROFS;
            goto out;
        }

        ret = ocfs2_truncate_rec(handle, et, path, index, dealloc,
                     cpos, len);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

out:
    ocfs2_free_path(path);
    return ret;
}

/*
 * ocfs2_reserve_blocks_for_rec_trunc() would look basically the
 * same as ocfs2_lock_alloctors(), except for it accepts a blocks
 * number to reserve some extra blocks, and it only handles meta
 * data allocations.
 *
 * Currently, only ocfs2_remove_btree_range() uses it for truncating
 * and punching holes.
 */
static int ocfs2_reserve_blocks_for_rec_trunc(struct inode *inode,
                          struct ocfs2_extent_tree *et,
                          u32 extents_to_split,
                          struct ocfs2_alloc_context **ac,
                          int extra_blocks)
{
    int ret = 0, num_free_extents;
    unsigned int max_recs_needed = 2 * extents_to_split;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    *ac = NULL;

    num_free_extents = ocfs2_num_free_extents(osb, et);
    if (num_free_extents < 0) {
        ret = num_free_extents;
        mlog_errno(ret);
        goto out;
    }

    if (!num_free_extents ||
        (ocfs2_sparse_alloc(osb) && num_free_extents < max_recs_needed))
        extra_blocks += ocfs2_extend_meta_needed(et->et_root_el);

    if (extra_blocks) {
        ret = ocfs2_reserve_new_metadata_blocks(osb, extra_blocks, ac);
        if (ret < 0) {
            if (ret != -ENOSPC)
                mlog_errno(ret);
            goto out;
        }
    }

out:
    if (ret) {
        if (*ac) {
            ocfs2_free_alloc_context(*ac);
            *ac = NULL;
        }
    }

    return ret;
}

int ocfs2_remove_btree_range(struct inode *inode,
                 struct ocfs2_extent_tree *et,
                 u32 cpos, u32 phys_cpos, u32 len, int flags,
                 struct ocfs2_cached_dealloc_ctxt *dealloc,
                 u64 refcount_loc)
{
    int ret, credits = 0, extra_blocks = 0;
    u64 phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, phys_cpos);
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct inode *tl_inode = osb->osb_tl_inode;
    handle_t *handle;
    struct ocfs2_alloc_context *meta_ac = NULL;
    struct ocfs2_refcount_tree *ref_tree = NULL;

    if ((flags & OCFS2_EXT_REFCOUNTED) && len) {
        BUG_ON(!(OCFS2_I(inode)->ip_dyn_features &
             OCFS2_HAS_REFCOUNT_FL));

        ret = ocfs2_lock_refcount_tree(osb, refcount_loc, 1,
                           &ref_tree, NULL);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_prepare_refcount_change_for_del(inode,
                                refcount_loc,
                                phys_blkno,
                                len,
                                &credits,
                                &extra_blocks);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

    ret = ocfs2_reserve_blocks_for_rec_trunc(inode, et, 1, &meta_ac,
                         extra_blocks);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    mutex_lock(&tl_inode->i_mutex);

    if (ocfs2_truncate_log_needs_flush(osb)) {
        ret = __ocfs2_flush_truncate_log(osb);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

    handle = ocfs2_start_trans(osb,
            ocfs2_remove_extent_credits(osb->sb) + credits);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_et_root_journal_access(handle, et,
                       OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    dquot_free_space_nodirty(inode,
                  ocfs2_clusters_to_bytes(inode->i_sb, len));

    ret = ocfs2_remove_extent(handle, et, cpos, len, meta_ac, dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    ocfs2_et_update_clusters(et, -len);

    ocfs2_journal_dirty(handle, et->et_root_bh);

    if (phys_blkno) {
        if (flags & OCFS2_EXT_REFCOUNTED)
            ret = ocfs2_decrease_refcount(inode, handle,
                    ocfs2_blocks_to_clusters(osb->sb,
                                 phys_blkno),
                    len, meta_ac,
                    dealloc, 1);
        else
            ret = ocfs2_truncate_log_append(osb, handle,
                            phys_blkno, len);
        if (ret)
            mlog_errno(ret);

    }

out_commit:
    ocfs2_commit_trans(osb, handle);
out:
    mutex_unlock(&tl_inode->i_mutex);

    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);

    if (ref_tree)
        ocfs2_unlock_refcount_tree(osb, ref_tree, 1);

    return ret;
}

int ocfs2_truncate_log_needs_flush(struct ocfs2_super *osb)
{
    struct buffer_head *tl_bh = osb->osb_tl_bh;
    struct ocfs2_dinode *di;
    struct ocfs2_truncate_log *tl;

    di = (struct ocfs2_dinode *) tl_bh->b_data;
    tl = &di->id2.i_dealloc;

    mlog_bug_on_msg(le16_to_cpu(tl->tl_used) > le16_to_cpu(tl->tl_count),
            "slot %d, invalid truncate log parameters: used = "
            "%u, count = %u\n", osb->slot_num,
            le16_to_cpu(tl->tl_used), le16_to_cpu(tl->tl_count));
    return le16_to_cpu(tl->tl_used) == le16_to_cpu(tl->tl_count);
}

static int ocfs2_truncate_log_can_coalesce(struct ocfs2_truncate_log *tl,
                       unsigned int new_start)
{
    unsigned int tail_index;
    unsigned int current_tail;

    /* No records, nothing to coalesce */
    if (!le16_to_cpu(tl->tl_used))
        return 0;

    tail_index = le16_to_cpu(tl->tl_used) - 1;
    current_tail = le32_to_cpu(tl->tl_recs[tail_index].t_start);
    current_tail += le32_to_cpu(tl->tl_recs[tail_index].t_clusters);

    return current_tail == new_start;
}

int ocfs2_truncate_log_append(struct ocfs2_super *osb,
                  handle_t *handle,
                  u64 start_blk,
                  unsigned int num_clusters)
{
    int status, index;
    unsigned int start_cluster, tl_count;
    struct inode *tl_inode = osb->osb_tl_inode;
    struct buffer_head *tl_bh = osb->osb_tl_bh;
    struct ocfs2_dinode *di;
    struct ocfs2_truncate_log *tl;

    BUG_ON(mutex_trylock(&tl_inode->i_mutex));

    start_cluster = ocfs2_blocks_to_clusters(osb->sb, start_blk);

    di = (struct ocfs2_dinode *) tl_bh->b_data;

    /* tl_bh is loaded from ocfs2_truncate_log_init().  It's validated
     * by the underlying call to ocfs2_read_inode_block(), so any
     * corruption is a code bug */
    BUG_ON(!OCFS2_IS_VALID_DINODE(di));

    tl = &di->id2.i_dealloc;
    tl_count = le16_to_cpu(tl->tl_count);
    mlog_bug_on_msg(tl_count > ocfs2_truncate_recs_per_inode(osb->sb) ||
            tl_count == 0,
            "Truncate record count on #%llu invalid "
            "wanted %u, actual %u\n",
            (unsigned long long)OCFS2_I(tl_inode)->ip_blkno,
            ocfs2_truncate_recs_per_inode(osb->sb),
            le16_to_cpu(tl->tl_count));

    /* Caller should have known to flush before calling us. */
    index = le16_to_cpu(tl->tl_used);
    if (index >= tl_count) {
        status = -ENOSPC;
        mlog_errno(status);
        goto bail;
    }

    status = ocfs2_journal_access_di(handle, INODE_CACHE(tl_inode), tl_bh,
                     OCFS2_JOURNAL_ACCESS_WRITE);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    trace_ocfs2_truncate_log_append(
        (unsigned long long)OCFS2_I(tl_inode)->ip_blkno, index,
        start_cluster, num_clusters);
    if (ocfs2_truncate_log_can_coalesce(tl, start_cluster)) {
        /*
         * Move index back to the record we are coalescing with.
         * ocfs2_truncate_log_can_coalesce() guarantees nonzero
         */
        index--;

        num_clusters += le32_to_cpu(tl->tl_recs[index].t_clusters);
        trace_ocfs2_truncate_log_append(
            (unsigned long long)OCFS2_I(tl_inode)->ip_blkno,
            index, le32_to_cpu(tl->tl_recs[index].t_start),
            num_clusters);
    } else {
        tl->tl_recs[index].t_start = cpu_to_le32(start_cluster);
        tl->tl_used = cpu_to_le16(index + 1);
    }
    tl->tl_recs[index].t_clusters = cpu_to_le32(num_clusters);

    ocfs2_journal_dirty(handle, tl_bh);

    osb->truncated_clusters += num_clusters;
bail:
    return status;
}

static int ocfs2_replay_truncate_records(struct ocfs2_super *osb,
                     handle_t *handle,
                     struct inode *data_alloc_inode,
                     struct buffer_head *data_alloc_bh)
{
    int status = 0;
    int i;
    unsigned int num_clusters;
    u64 start_blk;
    struct ocfs2_truncate_rec rec;
    struct ocfs2_dinode *di;
    struct ocfs2_truncate_log *tl;
    struct inode *tl_inode = osb->osb_tl_inode;
    struct buffer_head *tl_bh = osb->osb_tl_bh;

    di = (struct ocfs2_dinode *) tl_bh->b_data;
    tl = &di->id2.i_dealloc;
    i = le16_to_cpu(tl->tl_used) - 1;
    while (i >= 0) {
        /* Caller has given us at least enough credits to
         * update the truncate log dinode */
        status = ocfs2_journal_access_di(handle, INODE_CACHE(tl_inode), tl_bh,
                         OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }

        tl->tl_used = cpu_to_le16(i);

        ocfs2_journal_dirty(handle, tl_bh);

        /* TODO: Perhaps we can calculate the bulk of the
         * credits up front rather than extending like
         * this. */
        status = ocfs2_extend_trans(handle,
                        OCFS2_TRUNCATE_LOG_FLUSH_ONE_REC);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }

        rec = tl->tl_recs[i];
        start_blk = ocfs2_clusters_to_blocks(data_alloc_inode->i_sb,
                            le32_to_cpu(rec.t_start));
        num_clusters = le32_to_cpu(rec.t_clusters);

        /* if start_blk is not set, we ignore the record as
         * invalid. */
        if (start_blk) {
            trace_ocfs2_replay_truncate_records(
                (unsigned long long)OCFS2_I(tl_inode)->ip_blkno,
                i, le32_to_cpu(rec.t_start), num_clusters);

            status = ocfs2_free_clusters(handle, data_alloc_inode,
                             data_alloc_bh, start_blk,
                             num_clusters);
            if (status < 0) {
                mlog_errno(status);
                goto bail;
            }
        }
        i--;
    }

    osb->truncated_clusters = 0;

bail:
    return status;
}

/* Expects you to already be holding tl_inode->i_mutex */
int __ocfs2_flush_truncate_log(struct ocfs2_super *osb)
{
    int status;
    unsigned int num_to_flush;
    handle_t *handle;
    struct inode *tl_inode = osb->osb_tl_inode;
    struct inode *data_alloc_inode = NULL;
    struct buffer_head *tl_bh = osb->osb_tl_bh;
    struct buffer_head *data_alloc_bh = NULL;
    struct ocfs2_dinode *di;
    struct ocfs2_truncate_log *tl;

    BUG_ON(mutex_trylock(&tl_inode->i_mutex));

    di = (struct ocfs2_dinode *) tl_bh->b_data;

    /* tl_bh is loaded from ocfs2_truncate_log_init().  It's validated
     * by the underlying call to ocfs2_read_inode_block(), so any
     * corruption is a code bug */
    BUG_ON(!OCFS2_IS_VALID_DINODE(di));

    tl = &di->id2.i_dealloc;
    num_to_flush = le16_to_cpu(tl->tl_used);
    trace_ocfs2_flush_truncate_log(
        (unsigned long long)OCFS2_I(tl_inode)->ip_blkno,
        num_to_flush);
    if (!num_to_flush) {
        status = 0;
        goto out;
    }

    data_alloc_inode = ocfs2_get_system_file_inode(osb,
                               GLOBAL_BITMAP_SYSTEM_INODE,
                               OCFS2_INVALID_SLOT);
    if (!data_alloc_inode) {
        status = -EINVAL;
        mlog(ML_ERROR, "Could not get bitmap inode!\n");
        goto out;
    }

    mutex_lock(&data_alloc_inode->i_mutex);

    status = ocfs2_inode_lock(data_alloc_inode, &data_alloc_bh, 1);
    if (status < 0) {
        mlog_errno(status);
        goto out_mutex;
    }

    handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
    if (IS_ERR(handle)) {
        status = PTR_ERR(handle);
        mlog_errno(status);
        goto out_unlock;
    }

    status = ocfs2_replay_truncate_records(osb, handle, data_alloc_inode,
                           data_alloc_bh);
    if (status < 0)
        mlog_errno(status);

    ocfs2_commit_trans(osb, handle);

out_unlock:
    brelse(data_alloc_bh);
    ocfs2_inode_unlock(data_alloc_inode, 1);

out_mutex:
    mutex_unlock(&data_alloc_inode->i_mutex);
    iput(data_alloc_inode);

out:
    return status;
}

int ocfs2_flush_truncate_log(struct ocfs2_super *osb)
{
    int status;
    struct inode *tl_inode = osb->osb_tl_inode;

    mutex_lock(&tl_inode->i_mutex);
    status = __ocfs2_flush_truncate_log(osb);
    mutex_unlock(&tl_inode->i_mutex);

    return status;
}

static void ocfs2_truncate_log_worker(struct work_struct *work)
{
    int status;
    struct ocfs2_super *osb =
        container_of(work, struct ocfs2_super,
                 osb_truncate_log_wq.work);

    status = ocfs2_flush_truncate_log(osb);
    if (status < 0)
        mlog_errno(status);
    else
        ocfs2_init_steal_slots(osb);
}

#define OCFS2_TRUNCATE_LOG_FLUSH_INTERVAL (2 * HZ)
void ocfs2_schedule_truncate_log_flush(struct ocfs2_super *osb,
                       int cancel)
{
    if (osb->osb_tl_inode) {
        /* We want to push off log flushes while truncates are
         * still running. */
        if (cancel)
            cancel_delayed_work(&osb->osb_truncate_log_wq);

        queue_delayed_work(ocfs2_wq, &osb->osb_truncate_log_wq,
                   OCFS2_TRUNCATE_LOG_FLUSH_INTERVAL);
    }
}

static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
                       int slot_num,
                       struct inode **tl_inode,
                       struct buffer_head **tl_bh)
{
    int status;
    struct inode *inode = NULL;
    struct buffer_head *bh = NULL;

    inode = ocfs2_get_system_file_inode(osb,
                       TRUNCATE_LOG_SYSTEM_INODE,
                       slot_num);
    if (!inode) {
        status = -EINVAL;
        mlog(ML_ERROR, "Could not get load truncate log inode!\n");
        goto bail;
    }

    status = ocfs2_read_inode_block(inode, &bh);
    if (status < 0) {
        iput(inode);
        mlog_errno(status);
        goto bail;
    }

    *tl_inode = inode;
    *tl_bh    = bh;
bail:
    return status;
}

/* called during the 1st stage of node recovery. we stamp a clean
 * truncate log and pass back a copy for processing later. if the
 * truncate log does not require processing, a *tl_copy is set to
 * NULL. */
int ocfs2_begin_truncate_log_recovery(struct ocfs2_super *osb,
                      int slot_num,
                      struct ocfs2_dinode **tl_copy)
{
    int status;
    struct inode *tl_inode = NULL;
    struct buffer_head *tl_bh = NULL;
    struct ocfs2_dinode *di;
    struct ocfs2_truncate_log *tl;

    *tl_copy = NULL;

    trace_ocfs2_begin_truncate_log_recovery(slot_num);

    status = ocfs2_get_truncate_log_info(osb, slot_num, &tl_inode, &tl_bh);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    di = (struct ocfs2_dinode *) tl_bh->b_data;

    /* tl_bh is loaded from ocfs2_get_truncate_log_info().  It's
     * validated by the underlying call to ocfs2_read_inode_block(),
     * so any corruption is a code bug */
    BUG_ON(!OCFS2_IS_VALID_DINODE(di));

    tl = &di->id2.i_dealloc;
    if (le16_to_cpu(tl->tl_used)) {
        trace_ocfs2_truncate_log_recovery_num(le16_to_cpu(tl->tl_used));

        *tl_copy = kmalloc(tl_bh->b_size, GFP_KERNEL);
        if (!(*tl_copy)) {
            status = -ENOMEM;
            mlog_errno(status);
            goto bail;
        }

        /* Assuming the write-out below goes well, this copy
         * will be passed back to recovery for processing. */
        memcpy(*tl_copy, tl_bh->b_data, tl_bh->b_size);

        /* All we need to do to clear the truncate log is set
         * tl_used. */
        tl->tl_used = 0;

        ocfs2_compute_meta_ecc(osb->sb, tl_bh->b_data, &di->i_check);
        status = ocfs2_write_block(osb, tl_bh, INODE_CACHE(tl_inode));
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }
    }

bail:
    if (tl_inode)
        iput(tl_inode);
    brelse(tl_bh);

    if (status < 0 && (*tl_copy)) {
        kfree(*tl_copy);
        *tl_copy = NULL;
        mlog_errno(status);
    }

    return status;
}

int ocfs2_complete_truncate_log_recovery(struct ocfs2_super *osb,
                     struct ocfs2_dinode *tl_copy)
{
    int status = 0;
    int i;
    unsigned int clusters, num_recs, start_cluster;
    u64 start_blk;
    handle_t *handle;
    struct inode *tl_inode = osb->osb_tl_inode;
    struct ocfs2_truncate_log *tl;

    if (OCFS2_I(tl_inode)->ip_blkno == le64_to_cpu(tl_copy->i_blkno)) {
        mlog(ML_ERROR, "Asked to recover my own truncate log!\n");
        return -EINVAL;
    }

    tl = &tl_copy->id2.i_dealloc;
    num_recs = le16_to_cpu(tl->tl_used);
    trace_ocfs2_complete_truncate_log_recovery(
        (unsigned long long)le64_to_cpu(tl_copy->i_blkno),
        num_recs);

    mutex_lock(&tl_inode->i_mutex);
    for(i = 0; i < num_recs; i++) {
        if (ocfs2_truncate_log_needs_flush(osb)) {
            status = __ocfs2_flush_truncate_log(osb);
            if (status < 0) {
                mlog_errno(status);
                goto bail_up;
            }
        }

        handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
        if (IS_ERR(handle)) {
            status = PTR_ERR(handle);
            mlog_errno(status);
            goto bail_up;
        }

        clusters = le32_to_cpu(tl->tl_recs[i].t_clusters);
        start_cluster = le32_to_cpu(tl->tl_recs[i].t_start);
        start_blk = ocfs2_clusters_to_blocks(osb->sb, start_cluster);

        status = ocfs2_truncate_log_append(osb, handle,
                           start_blk, clusters);
        ocfs2_commit_trans(osb, handle);
        if (status < 0) {
            mlog_errno(status);
            goto bail_up;
        }
    }

bail_up:
    mutex_unlock(&tl_inode->i_mutex);

    return status;
}

void ocfs2_truncate_log_shutdown(struct ocfs2_super *osb)
{
    int status;
    struct inode *tl_inode = osb->osb_tl_inode;

    if (tl_inode) {
        cancel_delayed_work(&osb->osb_truncate_log_wq);
        flush_workqueue(ocfs2_wq);

        status = ocfs2_flush_truncate_log(osb);
        if (status < 0)
            mlog_errno(status);

        brelse(osb->osb_tl_bh);
        iput(osb->osb_tl_inode);
    }
}

int ocfs2_truncate_log_init(struct ocfs2_super *osb)
{
    int status;
    struct inode *tl_inode = NULL;
    struct buffer_head *tl_bh = NULL;

    status = ocfs2_get_truncate_log_info(osb,
                         osb->slot_num,
                         &tl_inode,
                         &tl_bh);
    if (status < 0)
        mlog_errno(status);

    /* ocfs2_truncate_log_shutdown keys on the existence of
     * osb->osb_tl_inode so we don't set any of the osb variables
     * until we're sure all is well. */
    INIT_DELAYED_WORK(&osb->osb_truncate_log_wq,
              ocfs2_truncate_log_worker);
    osb->osb_tl_bh    = tl_bh;
    osb->osb_tl_inode = tl_inode;

    return status;
}

/*
 * Delayed de-allocation of suballocator blocks.
 *
 * Some sets of block de-allocations might involve multiple suballocator inodes.
 *
 * The locking for this can get extremely complicated, especially when
 * the suballocator inodes to delete from aren't known until deep
 * within an unrelated codepath.
 *
 * ocfs2_extent_block structures are a good example of this - an inode
 * btree could have been grown by any number of nodes each allocating
 * out of their own suballoc inode.
 *
 * These structures allow the delay of block de-allocation until a
 * later time, when locking of multiple cluster inodes won't cause
 * deadlock.
 */

/*
 * Describe a single bit freed from a suballocator.  For the block
 * suballocators, it represents one block.  For the global cluster
 * allocator, it represents some clusters and free_bit indicates
 * clusters number.
 */
struct ocfs2_cached_block_free {
    struct ocfs2_cached_block_free      *free_next;
    u64                 free_bg;
    u64                 free_blk;
    unsigned int                free_bit;
};

struct ocfs2_per_slot_free_list {
    struct ocfs2_per_slot_free_list     *f_next_suballocator;
    int                 f_inode_type;
    int                 f_slot;
    struct ocfs2_cached_block_free      *f_first;
};

static int ocfs2_free_cached_blocks(struct ocfs2_super *osb,
                    int sysfile_type,
                    int slot,
                    struct ocfs2_cached_block_free *head)
{
    int ret;
    u64 bg_blkno;
    handle_t *handle;
    struct inode *inode;
    struct buffer_head *di_bh = NULL;
    struct ocfs2_cached_block_free *tmp;

    inode = ocfs2_get_system_file_inode(osb, sysfile_type, slot);
    if (!inode) {
        ret = -EINVAL;
        mlog_errno(ret);
        goto out;
    }

    mutex_lock(&inode->i_mutex);

    ret = ocfs2_inode_lock(inode, &di_bh, 1);
    if (ret) {
        mlog_errno(ret);
        goto out_mutex;
    }

    handle = ocfs2_start_trans(osb, OCFS2_SUBALLOC_FREE);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out_unlock;
    }

    while (head) {
        if (head->free_bg)
            bg_blkno = head->free_bg;
        else
            bg_blkno = ocfs2_which_suballoc_group(head->free_blk,
                                  head->free_bit);
        trace_ocfs2_free_cached_blocks(
             (unsigned long long)head->free_blk, head->free_bit);

        ret = ocfs2_free_suballoc_bits(handle, inode, di_bh,
                           head->free_bit, bg_blkno, 1);
        if (ret) {
            mlog_errno(ret);
            goto out_journal;
        }

        ret = ocfs2_extend_trans(handle, OCFS2_SUBALLOC_FREE);
        if (ret) {
            mlog_errno(ret);
            goto out_journal;
        }

        tmp = head;
        head = head->free_next;
        kfree(tmp);
    }

out_journal:
    ocfs2_commit_trans(osb, handle);

out_unlock:
    ocfs2_inode_unlock(inode, 1);
    brelse(di_bh);
out_mutex:
    mutex_unlock(&inode->i_mutex);
    iput(inode);
out:
    while(head) {
        /* Premature exit may have left some dangling items. */
        tmp = head;
        head = head->free_next;
        kfree(tmp);
    }

    return ret;
}

int ocfs2_cache_cluster_dealloc(struct ocfs2_cached_dealloc_ctxt *ctxt,
                u64 blkno, unsigned int bit)
{
    int ret = 0;
    struct ocfs2_cached_block_free *item;

    item = kzalloc(sizeof(*item), GFP_NOFS);
    if (item == NULL) {
        ret = -ENOMEM;
        mlog_errno(ret);
        return ret;
    }

    trace_ocfs2_cache_cluster_dealloc((unsigned long long)blkno, bit);

    item->free_blk = blkno;
    item->free_bit = bit;
    item->free_next = ctxt->c_global_allocator;

    ctxt->c_global_allocator = item;
    return ret;
}

static int ocfs2_free_cached_clusters(struct ocfs2_super *osb,
                      struct ocfs2_cached_block_free *head)
{
    struct ocfs2_cached_block_free *tmp;
    struct inode *tl_inode = osb->osb_tl_inode;
    handle_t *handle;
    int ret = 0;

    mutex_lock(&tl_inode->i_mutex);

    while (head) {
        if (ocfs2_truncate_log_needs_flush(osb)) {
            ret = __ocfs2_flush_truncate_log(osb);
            if (ret < 0) {
                mlog_errno(ret);
                break;
            }
        }

        handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
        if (IS_ERR(handle)) {
            ret = PTR_ERR(handle);
            mlog_errno(ret);
            break;
        }

        ret = ocfs2_truncate_log_append(osb, handle, head->free_blk,
                        head->free_bit);

        ocfs2_commit_trans(osb, handle);
        tmp = head;
        head = head->free_next;
        kfree(tmp);

        if (ret < 0) {
            mlog_errno(ret);
            break;
        }
    }

    mutex_unlock(&tl_inode->i_mutex);

    while (head) {
        /* Premature exit may have left some dangling items. */
        tmp = head;
        head = head->free_next;
        kfree(tmp);
    }

    return ret;
}

int ocfs2_run_deallocs(struct ocfs2_super *osb,
               struct ocfs2_cached_dealloc_ctxt *ctxt)
{
    int ret = 0, ret2;
    struct ocfs2_per_slot_free_list *fl;

    if (!ctxt)
        return 0;

    while (ctxt->c_first_suballocator) {
        fl = ctxt->c_first_suballocator;

        if (fl->f_first) {
            trace_ocfs2_run_deallocs(fl->f_inode_type,
                         fl->f_slot);
            ret2 = ocfs2_free_cached_blocks(osb,
                            fl->f_inode_type,
                            fl->f_slot,
                            fl->f_first);
            if (ret2)
                mlog_errno(ret2);
            if (!ret)
                ret = ret2;
        }

        ctxt->c_first_suballocator = fl->f_next_suballocator;
        kfree(fl);
    }

    if (ctxt->c_global_allocator) {
        ret2 = ocfs2_free_cached_clusters(osb,
                          ctxt->c_global_allocator);
        if (ret2)
            mlog_errno(ret2);
        if (!ret)
            ret = ret2;

        ctxt->c_global_allocator = NULL;
    }

    return ret;
}

static struct ocfs2_per_slot_free_list *
ocfs2_find_per_slot_free_list(int type,
                  int slot,
                  struct ocfs2_cached_dealloc_ctxt *ctxt)
{
    struct ocfs2_per_slot_free_list *fl = ctxt->c_first_suballocator;

    while (fl) {
        if (fl->f_inode_type == type && fl->f_slot == slot)
            return fl;

        fl = fl->f_next_suballocator;
    }

    fl = kmalloc(sizeof(*fl), GFP_NOFS);
    if (fl) {
        fl->f_inode_type = type;
        fl->f_slot = slot;
        fl->f_first = NULL;
        fl->f_next_suballocator = ctxt->c_first_suballocator;

        ctxt->c_first_suballocator = fl;
    }
    return fl;
}

int ocfs2_cache_block_dealloc(struct ocfs2_cached_dealloc_ctxt *ctxt,
                  int type, int slot, u64 suballoc,
                  u64 blkno, unsigned int bit)
{
    int ret;
    struct ocfs2_per_slot_free_list *fl;
    struct ocfs2_cached_block_free *item;

    fl = ocfs2_find_per_slot_free_list(type, slot, ctxt);
    if (fl == NULL) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    item = kzalloc(sizeof(*item), GFP_NOFS);
    if (item == NULL) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_cache_block_dealloc(type, slot,
                    (unsigned long long)suballoc,
                    (unsigned long long)blkno, bit);

    item->free_bg = suballoc;
    item->free_blk = blkno;
    item->free_bit = bit;
    item->free_next = fl->f_first;

    fl->f_first = item;

    ret = 0;
out:
    return ret;
}

static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
                     struct ocfs2_extent_block *eb)
{
    return ocfs2_cache_block_dealloc(ctxt, EXTENT_ALLOC_SYSTEM_INODE,
                     le16_to_cpu(eb->h_suballoc_slot),
                     le64_to_cpu(eb->h_suballoc_loc),
                     le64_to_cpu(eb->h_blkno),
                     le16_to_cpu(eb->h_suballoc_bit));
}

static int ocfs2_zero_func(handle_t *handle, struct buffer_head *bh)
{
    set_buffer_uptodate(bh);
    mark_buffer_dirty(bh);
    return 0;
}

void ocfs2_map_and_dirty_page(struct inode *inode, handle_t *handle,
                  unsigned int from, unsigned int to,
                  struct page *page, int zero, u64 *phys)
{
    int ret, partial = 0;

    ret = ocfs2_map_page_blocks(page, phys, inode, from, to, 0);
    if (ret)
        mlog_errno(ret);

    if (zero)
        zero_user_segment(page, from, to);

    /*
     * Need to set the buffers we zero'd into uptodate
     * here if they aren't - ocfs2_map_page_blocks()
     * might've skipped some
     */
    ret = walk_page_buffers(handle, page_buffers(page),
                from, to, &partial,
                ocfs2_zero_func);
    if (ret < 0)
        mlog_errno(ret);
    else if (ocfs2_should_order_data(inode)) {
        ret = ocfs2_jbd2_file_inode(handle, inode);
        if (ret < 0)
            mlog_errno(ret);
    }

    if (!partial)
        SetPageUptodate(page);

    flush_dcache_page(page);
}

static void ocfs2_zero_cluster_pages(struct inode *inode, loff_t start,
                     loff_t end, struct page **pages,
                     int numpages, u64 phys, handle_t *handle)
{
    int i;
    struct page *page;
    unsigned int from, to = PAGE_CACHE_SIZE;
    struct super_block *sb = inode->i_sb;

    BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(sb)));

    if (numpages == 0)
        goto out;

    to = PAGE_CACHE_SIZE;
    for(i = 0; i < numpages; i++) {
        page = pages[i];

        from = start & (PAGE_CACHE_SIZE - 1);
        if ((end >> PAGE_CACHE_SHIFT) == page->index)
            to = end & (PAGE_CACHE_SIZE - 1);

        BUG_ON(from > PAGE_CACHE_SIZE);
        BUG_ON(to > PAGE_CACHE_SIZE);

        ocfs2_map_and_dirty_page(inode, handle, from, to, page, 1,
                     &phys);

        start = (page->index + 1) << PAGE_CACHE_SHIFT;
    }
out:
    if (pages)
        ocfs2_unlock_and_free_pages(pages, numpages);
}

int ocfs2_grab_pages(struct inode *inode, loff_t start, loff_t end,
             struct page **pages, int *num)
{
    int numpages, ret = 0;
    struct address_space *mapping = inode->i_mapping;
    unsigned long index;
    loff_t last_page_bytes;

    BUG_ON(start > end);

    numpages = 0;
    last_page_bytes = PAGE_ALIGN(end);
    index = start >> PAGE_CACHE_SHIFT;
    do {
        pages[numpages] = find_or_create_page(mapping, index, GFP_NOFS);
        if (!pages[numpages]) {
            ret = -ENOMEM;
            mlog_errno(ret);
            goto out;
        }

        numpages++;
        index++;
    } while (index < (last_page_bytes >> PAGE_CACHE_SHIFT));

out:
    if (ret != 0) {
        if (pages)
            ocfs2_unlock_and_free_pages(pages, numpages);
        numpages = 0;
    }

    *num = numpages;

    return ret;
}

static int ocfs2_grab_eof_pages(struct inode *inode, loff_t start, loff_t end,
                struct page **pages, int *num)
{
    struct super_block *sb = inode->i_sb;

    BUG_ON(start >> OCFS2_SB(sb)->s_clustersize_bits !=
           (end - 1) >> OCFS2_SB(sb)->s_clustersize_bits);

    return ocfs2_grab_pages(inode, start, end, pages, num);
}

/*
 * Zero the area past i_size but still within an allocated
 * cluster. This avoids exposing nonzero data on subsequent file
 * extends.
 *
 * We need to call this before i_size is updated on the inode because
 * otherwise block_write_full_page() will skip writeout of pages past
 * i_size. The new_i_size parameter is passed for this reason.
 */
int ocfs2_zero_range_for_truncate(struct inode *inode, handle_t *handle,
                  u64 range_start, u64 range_end)
{
    int ret = 0, numpages;
    struct page **pages = NULL;
    u64 phys;
    unsigned int ext_flags;
    struct super_block *sb = inode->i_sb;

    /*
     * File systems which don't support sparse files zero on every
     * extend.
     */
    if (!ocfs2_sparse_alloc(OCFS2_SB(sb)))
        return 0;

    pages = kcalloc(ocfs2_pages_per_cluster(sb),
            sizeof(struct page *), GFP_NOFS);
    if (pages == NULL) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    if (range_start == range_end)
        goto out;

    ret = ocfs2_extent_map_get_blocks(inode,
                      range_start >> sb->s_blocksize_bits,
                      &phys, NULL, &ext_flags);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * Tail is a hole, or is marked unwritten. In either case, we
     * can count on read and write to return/push zero's.
     */
    if (phys == 0 || ext_flags & OCFS2_EXT_UNWRITTEN)
        goto out;

    ret = ocfs2_grab_eof_pages(inode, range_start, range_end, pages,
                   &numpages);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_zero_cluster_pages(inode, range_start, range_end, pages,
                 numpages, phys, handle);

    /*
     * Initiate writeout of the pages we zero'd here. We don't
     * wait on them - the truncate_inode_pages() call later will
     * do that for us.
     */
    ret = filemap_fdatawrite_range(inode->i_mapping, range_start,
                       range_end - 1);
    if (ret)
        mlog_errno(ret);

out:
    if (pages)
        kfree(pages);

    return ret;
}

static void ocfs2_zero_dinode_id2_with_xattr(struct inode *inode,
                         struct ocfs2_dinode *di)
{
    unsigned int blocksize = 1 << inode->i_sb->s_blocksize_bits;
    unsigned int xattrsize = le16_to_cpu(di->i_xattr_inline_size);

    if (le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_XATTR_FL)
        memset(&di->id2, 0, blocksize -
                    offsetof(struct ocfs2_dinode, id2) -
                    xattrsize);
    else
        memset(&di->id2, 0, blocksize -
                    offsetof(struct ocfs2_dinode, id2));
}

void ocfs2_dinode_new_extent_list(struct inode *inode,
                  struct ocfs2_dinode *di)
{
    ocfs2_zero_dinode_id2_with_xattr(inode, di);
    di->id2.i_list.l_tree_depth = 0;
    di->id2.i_list.l_next_free_rec = 0;
    di->id2.i_list.l_count = cpu_to_le16(
        ocfs2_extent_recs_per_inode_with_xattr(inode->i_sb, di));
}

void ocfs2_set_inode_data_inline(struct inode *inode, struct ocfs2_dinode *di)
{
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_inline_data *idata = &di->id2.i_data;

    spin_lock(&oi->ip_lock);
    oi->ip_dyn_features |= OCFS2_INLINE_DATA_FL;
    di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
    spin_unlock(&oi->ip_lock);

    /*
     * We clear the entire i_data structure here so that all
     * fields can be properly initialized.
     */
    ocfs2_zero_dinode_id2_with_xattr(inode, di);

    idata->id_count = cpu_to_le16(
            ocfs2_max_inline_data_with_xattr(inode->i_sb, di));
}

int ocfs2_convert_inline_data_to_extents(struct inode *inode,
                     struct buffer_head *di_bh)
{
    int ret, i, has_data, num_pages = 0;
    handle_t *handle;
    u64 uninitialized_var(block);
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_alloc_context *data_ac = NULL;
    struct page **pages = NULL;
    loff_t end = osb->s_clustersize;
    struct ocfs2_extent_tree et;
    int did_quota = 0;

    has_data = i_size_read(inode) ? 1 : 0;

    if (has_data) {
        pages = kcalloc(ocfs2_pages_per_cluster(osb->sb),
                sizeof(struct page *), GFP_NOFS);
        if (pages == NULL) {
            ret = -ENOMEM;
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_reserve_clusters(osb, 1, &data_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    handle = ocfs2_start_trans(osb,
                   ocfs2_inline_to_extents_credits(osb->sb));
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out_unlock;
    }

    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    if (has_data) {
        u32 bit_off, num;
        unsigned int page_end;
        u64 phys;

        ret = dquot_alloc_space_nodirty(inode,
                       ocfs2_clusters_to_bytes(osb->sb, 1));
        if (ret)
            goto out_commit;
        did_quota = 1;

        data_ac->ac_resv = &OCFS2_I(inode)->ip_la_data_resv;

        ret = ocfs2_claim_clusters(handle, data_ac, 1, &bit_off,
                       &num);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        /*
         * Save two copies, one for insert, and one that can
         * be changed by ocfs2_map_and_dirty_page() below.
         */
        block = phys = ocfs2_clusters_to_blocks(inode->i_sb, bit_off);

        /*
         * Non sparse file systems zero on extend, so no need
         * to do that now.
         */
        if (!ocfs2_sparse_alloc(osb) &&
            PAGE_CACHE_SIZE < osb->s_clustersize)
            end = PAGE_CACHE_SIZE;

        ret = ocfs2_grab_eof_pages(inode, 0, end, pages, &num_pages);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        /*
         * This should populate the 1st page for us and mark
         * it up to date.
         */
        ret = ocfs2_read_inline_data(inode, pages[0], di_bh);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        page_end = PAGE_CACHE_SIZE;
        if (PAGE_CACHE_SIZE > osb->s_clustersize)
            page_end = osb->s_clustersize;

        for (i = 0; i < num_pages; i++)
            ocfs2_map_and_dirty_page(inode, handle, 0, page_end,
                         pages[i], i > 0, &phys);
    }

    spin_lock(&oi->ip_lock);
    oi->ip_dyn_features &= ~OCFS2_INLINE_DATA_FL;
    di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
    spin_unlock(&oi->ip_lock);

    ocfs2_dinode_new_extent_list(inode, di);

    ocfs2_journal_dirty(handle, di_bh);

    if (has_data) {
        /*
         * An error at this point should be extremely rare. If
         * this proves to be false, we could always re-build
         * the in-inode data from our pages.
         */
        ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
        ret = ocfs2_insert_extent(handle, &et, 0, block, 1, 0, NULL);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        inode->i_blocks = ocfs2_inode_sector_count(inode);
    }

out_commit:
    if (ret < 0 && did_quota)
        dquot_free_space_nodirty(inode,
                      ocfs2_clusters_to_bytes(osb->sb, 1));

    ocfs2_commit_trans(osb, handle);

out_unlock:
    if (data_ac)
        ocfs2_free_alloc_context(data_ac);

out:
    if (pages) {
        ocfs2_unlock_and_free_pages(pages, num_pages);
        kfree(pages);
    }

    return ret;
}

/*
 * It is expected, that by the time you call this function,
 * inode->i_size and fe->i_size have been adjusted.
 *
 * WARNING: This will kfree the truncate context
 */
int ocfs2_commit_truncate(struct ocfs2_super *osb,
              struct inode *inode,
              struct buffer_head *di_bh)
{
    int status = 0, i, flags = 0;
    u32 new_highest_cpos, range, trunc_cpos, trunc_len, phys_cpos, coff;
    u64 blkno = 0;
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec;
    struct ocfs2_path *path = NULL;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_extent_list *root_el = &(di->id2.i_list);
    u64 refcount_loc = le64_to_cpu(di->i_refcount_loc);
    struct ocfs2_extent_tree et;
    struct ocfs2_cached_dealloc_ctxt dealloc;

    ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
    ocfs2_init_dealloc_ctxt(&dealloc);

    new_highest_cpos = ocfs2_clusters_for_bytes(osb->sb,
                             i_size_read(inode));

    path = ocfs2_new_path(di_bh, &di->id2.i_list,
                  ocfs2_journal_access_di);
    if (!path) {
        status = -ENOMEM;
        mlog_errno(status);
        goto bail;
    }

    ocfs2_extent_map_trunc(inode, new_highest_cpos);

start:
    /*
     * Check that we still have allocation to delete.
     */
    if (OCFS2_I(inode)->ip_clusters == 0) {
        status = 0;
        goto bail;
    }

    /*
     * Truncate always works against the rightmost tree branch.
     */
    status = ocfs2_find_path(INODE_CACHE(inode), path, UINT_MAX);
    if (status) {
        mlog_errno(status);
        goto bail;
    }

    trace_ocfs2_commit_truncate(
        (unsigned long long)OCFS2_I(inode)->ip_blkno,
        new_highest_cpos,
        OCFS2_I(inode)->ip_clusters,
        path->p_tree_depth);

    /*
     * By now, el will point to the extent list on the bottom most
     * portion of this tree. Only the tail record is considered in
     * each pass.
     *
     * We handle the following cases, in order:
     * - empty extent: delete the remaining branch
     * - remove the entire record
     * - remove a partial record
     * - no record needs to be removed (truncate has completed)
     */
    el = path_leaf_el(path);
    if (le16_to_cpu(el->l_next_free_rec) == 0) {
        ocfs2_error(inode->i_sb,
                "Inode %llu has empty extent block at %llu\n",
                (unsigned long long)OCFS2_I(inode)->ip_blkno,
                (unsigned long long)path_leaf_bh(path)->b_blocknr);
        status = -EROFS;
        goto bail;
    }

    i = le16_to_cpu(el->l_next_free_rec) - 1;
    rec = &el->l_recs[i];
    flags = rec->e_flags;
    range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);

    if (i == 0 && ocfs2_is_empty_extent(rec)) {
        /*
         * Lower levels depend on this never happening, but it's best
         * to check it up here before changing the tree.
        */
        if (root_el->l_tree_depth && rec->e_int_clusters == 0) {
            ocfs2_error(inode->i_sb, "Inode %lu has an empty "
                    "extent record, depth %u\n", inode->i_ino,
                    le16_to_cpu(root_el->l_tree_depth));
            status = -EROFS;
            goto bail;
        }
        trunc_cpos = le32_to_cpu(rec->e_cpos);
        trunc_len = 0;
        blkno = 0;
    } else if (le32_to_cpu(rec->e_cpos) >= new_highest_cpos) {
        /*
         * Truncate entire record.
         */
        trunc_cpos = le32_to_cpu(rec->e_cpos);
        trunc_len = ocfs2_rec_clusters(el, rec);
        blkno = le64_to_cpu(rec->e_blkno);
    } else if (range > new_highest_cpos) {
        /*
         * Partial truncate. it also should be
         * the last truncate we're doing.
         */
        trunc_cpos = new_highest_cpos;
        trunc_len = range - new_highest_cpos;
        coff = new_highest_cpos - le32_to_cpu(rec->e_cpos);
        blkno = le64_to_cpu(rec->e_blkno) +
                ocfs2_clusters_to_blocks(inode->i_sb, coff);
    } else {
        /*
         * Truncate completed, leave happily.
         */
        status = 0;
        goto bail;
    }

    phys_cpos = ocfs2_blocks_to_clusters(inode->i_sb, blkno);

    status = ocfs2_remove_btree_range(inode, &et, trunc_cpos,
                      phys_cpos, trunc_len, flags, &dealloc,
                      refcount_loc);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    ocfs2_reinit_path(path, 1);

    /*
     * The check above will catch the case where we've truncated
     * away all allocation.
     */
    goto start;

bail:

    ocfs2_schedule_truncate_log_flush(osb, 1);

    ocfs2_run_deallocs(osb, &dealloc);

    ocfs2_free_path(path);

    return status;
}

/*
 * 'start' is inclusive, 'end' is not.
 */
int ocfs2_truncate_inline(struct inode *inode, struct buffer_head *di_bh,
              unsigned int start, unsigned int end, int trunc)
{
    int ret;
    unsigned int numbytes;
    handle_t *handle;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_inline_data *idata = &di->id2.i_data;

    if (end > i_size_read(inode))
        end = i_size_read(inode);

    BUG_ON(start >= end);

    if (!(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) ||
        !(le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) ||
        !ocfs2_supports_inline_data(osb)) {
        ocfs2_error(inode->i_sb,
                "Inline data flags for inode %llu don't agree! "
                "Disk: 0x%x, Memory: 0x%x, Superblock: 0x%x\n",
                (unsigned long long)OCFS2_I(inode)->ip_blkno,
                le16_to_cpu(di->i_dyn_features),
                OCFS2_I(inode)->ip_dyn_features,
                osb->s_feature_incompat);
        ret = -EROFS;
        goto out;
    }

    handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    numbytes = end - start;
    memset(idata->id_data + start, 0, numbytes);

    /*
     * No need to worry about the data page here - it's been
     * truncated already and inline data doesn't need it for
     * pushing zero's to disk, so we'll let readpage pick it up
     * later.
     */
    if (trunc) {
        i_size_write(inode, start);
        di->i_size = cpu_to_le64(start);
    }

    inode->i_blocks = ocfs2_inode_sector_count(inode);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME;

    di->i_ctime = di->i_mtime = cpu_to_le64(inode->i_ctime.tv_sec);
    di->i_ctime_nsec = di->i_mtime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);

    ocfs2_journal_dirty(handle, di_bh);

out_commit:
    ocfs2_commit_trans(osb, handle);

out:
    return ret;
}

static int ocfs2_trim_extent(struct super_block *sb,
                 struct ocfs2_group_desc *gd,
                 u32 start, u32 count)
{
    u64 discard, bcount;

    bcount = ocfs2_clusters_to_blocks(sb, count);
    discard = le64_to_cpu(gd->bg_blkno) +
            ocfs2_clusters_to_blocks(sb, start);

    trace_ocfs2_trim_extent(sb, (unsigned long long)discard, bcount);

    return sb_issue_discard(sb, discard, bcount, GFP_NOFS, 0);
}

static int ocfs2_trim_group(struct super_block *sb,
                struct ocfs2_group_desc *gd,
                u32 start, u32 max, u32 minbits)
{
    int ret = 0, count = 0, next;
    void *bitmap = gd->bg_bitmap;

    if (le16_to_cpu(gd->bg_free_bits_count) < minbits)
        return 0;

    trace_ocfs2_trim_group((unsigned long long)le64_to_cpu(gd->bg_blkno),
                   start, max, minbits);

    while (start < max) {
        start = ocfs2_find_next_zero_bit(bitmap, max, start);
        if (start >= max)
            break;
        next = ocfs2_find_next_bit(bitmap, max, start);

        if ((next - start) >= minbits) {
            ret = ocfs2_trim_extent(sb, gd,
                        start, next - start);
            if (ret < 0) {
                mlog_errno(ret);
                break;
            }
            count += next - start;
        }
        start = next + 1;

        if (fatal_signal_pending(current)) {
            count = -ERESTARTSYS;
            break;
        }

        if ((le16_to_cpu(gd->bg_free_bits_count) - count) < minbits)
            break;
    }

    if (ret < 0)
        count = ret;

    return count;
}

int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
{
    struct ocfs2_super *osb = OCFS2_SB(sb);
    u64 start, len, trimmed, first_group, last_group, group;
    int ret, cnt;
    u32 first_bit, last_bit, minlen;
    struct buffer_head *main_bm_bh = NULL;
    struct inode *main_bm_inode = NULL;
    struct buffer_head *gd_bh = NULL;
    struct ocfs2_dinode *main_bm;
    struct ocfs2_group_desc *gd = NULL;

    start = range->start >> osb->s_clustersize_bits;
    len = range->len >> osb->s_clustersize_bits;
    minlen = range->minlen >> osb->s_clustersize_bits;
    trimmed = 0;

    if (!len) {
        range->len = 0;
        return 0;
    }

    if (minlen >= osb->bitmap_cpg)
        return -EINVAL;

    main_bm_inode = ocfs2_get_system_file_inode(osb,
                            GLOBAL_BITMAP_SYSTEM_INODE,
                            OCFS2_INVALID_SLOT);
    if (!main_bm_inode) {
        ret = -EIO;
        mlog_errno(ret);
        goto out;
    }

    mutex_lock(&main_bm_inode->i_mutex);

    ret = ocfs2_inode_lock(main_bm_inode, &main_bm_bh, 0);
    if (ret < 0) {
        mlog_errno(ret);
        goto out_mutex;
    }
    main_bm = (struct ocfs2_dinode *)main_bm_bh->b_data;

    if (start >= le32_to_cpu(main_bm->i_clusters)) {
        ret = -EINVAL;
        goto out_unlock;
    }

    if (start + len > le32_to_cpu(main_bm->i_clusters))
        len = le32_to_cpu(main_bm->i_clusters) - start;

    trace_ocfs2_trim_fs(start, len, minlen);

    /* Determine first and last group to examine based on start and len */
    first_group = ocfs2_which_cluster_group(main_bm_inode, start);
    if (first_group == osb->first_cluster_group_blkno)
        first_bit = start;
    else
        first_bit = start - ocfs2_blocks_to_clusters(sb, first_group);
    last_group = ocfs2_which_cluster_group(main_bm_inode, start + len - 1);
    last_bit = osb->bitmap_cpg;

    for (group = first_group; group <= last_group;) {
        if (first_bit + len >= osb->bitmap_cpg)
            last_bit = osb->bitmap_cpg;
        else
            last_bit = first_bit + len;

        ret = ocfs2_read_group_descriptor(main_bm_inode,
                          main_bm, group,
                          &gd_bh);
        if (ret < 0) {
            mlog_errno(ret);
            break;
        }

        gd = (struct ocfs2_group_desc *)gd_bh->b_data;
        cnt = ocfs2_trim_group(sb, gd, first_bit, last_bit, minlen);
        brelse(gd_bh);
        gd_bh = NULL;
        if (cnt < 0) {
            ret = cnt;
            mlog_errno(ret);
            break;
        }

        trimmed += cnt;
        len -= osb->bitmap_cpg - first_bit;
        first_bit = 0;
        if (group == osb->first_cluster_group_blkno)
            group = ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
        else
            group += ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
    }
    range->len = trimmed * sb->s_blocksize;
out_unlock:
    ocfs2_inode_unlock(main_bm_inode, 0);
    brelse(main_bm_bh);
out_mutex:
    mutex_unlock(&main_bm_inode->i_mutex);
    iput(main_bm_inode);
out:
    return ret;
}