refcounttree.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * refcounttree.c
 *
 * Copyright (C) 2009 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 version 2 as published by the Free Software Foundation.
 *
 * 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.
 */

#include <linux/sort.h>
#include <cluster/masklog.h>
#include "ocfs2.h"
#include "inode.h"
#include "alloc.h"
#include "suballoc.h"
#include "journal.h"
#include "uptodate.h"
#include "super.h"
#include "buffer_head_io.h"
#include "blockcheck.h"
#include "refcounttree.h"
#include "sysfile.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "aops.h"
#include "xattr.h"
#include "namei.h"
#include "ocfs2_trace.h"

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/swap.h>
#include <linux/security.h>
#include <linux/fsnotify.h>
#include <linux/quotaops.h>
#include <linux/namei.h>
#include <linux/mount.h>

struct ocfs2_cow_context {
    struct inode *inode;
    struct file *file;
    u32 cow_start;
    u32 cow_len;
    struct ocfs2_extent_tree data_et;
    struct ocfs2_refcount_tree *ref_tree;
    struct buffer_head *ref_root_bh;
    struct ocfs2_alloc_context *meta_ac;
    struct ocfs2_alloc_context *data_ac;
    struct ocfs2_cached_dealloc_ctxt dealloc;
    void *cow_object;
    struct ocfs2_post_refcount *post_refcount;
    int extra_credits;
    int (*get_clusters)(struct ocfs2_cow_context *context,
                u32 v_cluster, u32 *p_cluster,
                u32 *num_clusters,
                unsigned int *extent_flags);
    int (*cow_duplicate_clusters)(handle_t *handle,
                      struct file *file,
                      u32 cpos, u32 old_cluster,
                      u32 new_cluster, u32 new_len);
};

static inline struct ocfs2_refcount_tree *
cache_info_to_refcount(struct ocfs2_caching_info *ci)
{
    return container_of(ci, struct ocfs2_refcount_tree, rf_ci);
}

static int ocfs2_validate_refcount_block(struct super_block *sb,
                     struct buffer_head *bh)
{
    int rc;
    struct ocfs2_refcount_block *rb =
        (struct ocfs2_refcount_block *)bh->b_data;

    trace_ocfs2_validate_refcount_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, &rb->rf_check);
    if (rc) {
        mlog(ML_ERROR, "Checksum failed for refcount block %llu\n",
             (unsigned long long)bh->b_blocknr);
        return rc;
    }


    if (!OCFS2_IS_VALID_REFCOUNT_BLOCK(rb)) {
        ocfs2_error(sb,
                "Refcount block #%llu has bad signature %.*s",
                (unsigned long long)bh->b_blocknr, 7,
                rb->rf_signature);
        return -EINVAL;
    }

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

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

    return 0;
}

static int ocfs2_read_refcount_block(struct ocfs2_caching_info *ci,
                     u64 rb_blkno,
                     struct buffer_head **bh)
{
    int rc;
    struct buffer_head *tmp = *bh;

    rc = ocfs2_read_block(ci, rb_blkno, &tmp,
                  ocfs2_validate_refcount_block);

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

    return rc;
}

static u64 ocfs2_refcount_cache_owner(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    return rf->rf_blkno;
}

static struct super_block *
ocfs2_refcount_cache_get_super(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    return rf->rf_sb;
}

static void ocfs2_refcount_cache_lock(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    spin_lock(&rf->rf_lock);
}

static void ocfs2_refcount_cache_unlock(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    spin_unlock(&rf->rf_lock);
}

static void ocfs2_refcount_cache_io_lock(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    mutex_lock(&rf->rf_io_mutex);
}

static void ocfs2_refcount_cache_io_unlock(struct ocfs2_caching_info *ci)
{
    struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

    mutex_unlock(&rf->rf_io_mutex);
}

static const struct ocfs2_caching_operations ocfs2_refcount_caching_ops = {
    .co_owner       = ocfs2_refcount_cache_owner,
    .co_get_super       = ocfs2_refcount_cache_get_super,
    .co_cache_lock      = ocfs2_refcount_cache_lock,
    .co_cache_unlock    = ocfs2_refcount_cache_unlock,
    .co_io_lock     = ocfs2_refcount_cache_io_lock,
    .co_io_unlock       = ocfs2_refcount_cache_io_unlock,
};

static struct ocfs2_refcount_tree *
ocfs2_find_refcount_tree(struct ocfs2_super *osb, u64 blkno)
{
    struct rb_node *n = osb->osb_rf_lock_tree.rb_node;
    struct ocfs2_refcount_tree *tree = NULL;

    while (n) {
        tree = rb_entry(n, struct ocfs2_refcount_tree, rf_node);

        if (blkno < tree->rf_blkno)
            n = n->rb_left;
        else if (blkno > tree->rf_blkno)
            n = n->rb_right;
        else
            return tree;
    }

    return NULL;
}

/* osb_lock is already locked. */
static void ocfs2_insert_refcount_tree(struct ocfs2_super *osb,
                       struct ocfs2_refcount_tree *new)
{
    u64 rf_blkno = new->rf_blkno;
    struct rb_node *parent = NULL;
    struct rb_node **p = &osb->osb_rf_lock_tree.rb_node;
    struct ocfs2_refcount_tree *tmp;

    while (*p) {
        parent = *p;

        tmp = rb_entry(parent, struct ocfs2_refcount_tree,
                   rf_node);

        if (rf_blkno < tmp->rf_blkno)
            p = &(*p)->rb_left;
        else if (rf_blkno > tmp->rf_blkno)
            p = &(*p)->rb_right;
        else {
            /* This should never happen! */
            mlog(ML_ERROR, "Duplicate refcount block %llu found!\n",
                 (unsigned long long)rf_blkno);
            BUG();
        }
    }

    rb_link_node(&new->rf_node, parent, p);
    rb_insert_color(&new->rf_node, &osb->osb_rf_lock_tree);
}

static void ocfs2_free_refcount_tree(struct ocfs2_refcount_tree *tree)
{
    ocfs2_metadata_cache_exit(&tree->rf_ci);
    ocfs2_simple_drop_lockres(OCFS2_SB(tree->rf_sb), &tree->rf_lockres);
    ocfs2_lock_res_free(&tree->rf_lockres);
    kfree(tree);
}

static inline void
ocfs2_erase_refcount_tree_from_list_no_lock(struct ocfs2_super *osb,
                    struct ocfs2_refcount_tree *tree)
{
    rb_erase(&tree->rf_node, &osb->osb_rf_lock_tree);
    if (osb->osb_ref_tree_lru && osb->osb_ref_tree_lru == tree)
        osb->osb_ref_tree_lru = NULL;
}

static void ocfs2_erase_refcount_tree_from_list(struct ocfs2_super *osb,
                    struct ocfs2_refcount_tree *tree)
{
    spin_lock(&osb->osb_lock);
    ocfs2_erase_refcount_tree_from_list_no_lock(osb, tree);
    spin_unlock(&osb->osb_lock);
}

static void ocfs2_kref_remove_refcount_tree(struct kref *kref)
{
    struct ocfs2_refcount_tree *tree =
        container_of(kref, struct ocfs2_refcount_tree, rf_getcnt);

    ocfs2_free_refcount_tree(tree);
}

static inline void
ocfs2_refcount_tree_get(struct ocfs2_refcount_tree *tree)
{
    kref_get(&tree->rf_getcnt);
}

static inline void
ocfs2_refcount_tree_put(struct ocfs2_refcount_tree *tree)
{
    kref_put(&tree->rf_getcnt, ocfs2_kref_remove_refcount_tree);
}

static inline void ocfs2_init_refcount_tree_ci(struct ocfs2_refcount_tree *new,
                           struct super_block *sb)
{
    ocfs2_metadata_cache_init(&new->rf_ci, &ocfs2_refcount_caching_ops);
    mutex_init(&new->rf_io_mutex);
    new->rf_sb = sb;
    spin_lock_init(&new->rf_lock);
}

static inline void ocfs2_init_refcount_tree_lock(struct ocfs2_super *osb,
                    struct ocfs2_refcount_tree *new,
                    u64 rf_blkno, u32 generation)
{
    init_rwsem(&new->rf_sem);
    ocfs2_refcount_lock_res_init(&new->rf_lockres, osb,
                     rf_blkno, generation);
}

static struct ocfs2_refcount_tree*
ocfs2_allocate_refcount_tree(struct ocfs2_super *osb, u64 rf_blkno)
{
    struct ocfs2_refcount_tree *new;

    new = kzalloc(sizeof(struct ocfs2_refcount_tree), GFP_NOFS);
    if (!new)
        return NULL;

    new->rf_blkno = rf_blkno;
    kref_init(&new->rf_getcnt);
    ocfs2_init_refcount_tree_ci(new, osb->sb);

    return new;
}

static int ocfs2_get_refcount_tree(struct ocfs2_super *osb, u64 rf_blkno,
                   struct ocfs2_refcount_tree **ret_tree)
{
    int ret = 0;
    struct ocfs2_refcount_tree *tree, *new = NULL;
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_block *ref_rb;

    spin_lock(&osb->osb_lock);
    if (osb->osb_ref_tree_lru &&
        osb->osb_ref_tree_lru->rf_blkno == rf_blkno)
        tree = osb->osb_ref_tree_lru;
    else
        tree = ocfs2_find_refcount_tree(osb, rf_blkno);
    if (tree)
        goto out;

    spin_unlock(&osb->osb_lock);

    new = ocfs2_allocate_refcount_tree(osb, rf_blkno);
    if (!new) {
        ret = -ENOMEM;
        mlog_errno(ret);
        return ret;
    }
    /*
     * We need the generation to create the refcount tree lock and since
     * it isn't changed during the tree modification, we are safe here to
     * read without protection.
     * We also have to purge the cache after we create the lock since the
     * refcount block may have the stale data. It can only be trusted when
     * we hold the refcount lock.
     */
    ret = ocfs2_read_refcount_block(&new->rf_ci, rf_blkno, &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        ocfs2_metadata_cache_exit(&new->rf_ci);
        kfree(new);
        return ret;
    }

    ref_rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    new->rf_generation = le32_to_cpu(ref_rb->rf_generation);
    ocfs2_init_refcount_tree_lock(osb, new, rf_blkno,
                      new->rf_generation);
    ocfs2_metadata_cache_purge(&new->rf_ci);

    spin_lock(&osb->osb_lock);
    tree = ocfs2_find_refcount_tree(osb, rf_blkno);
    if (tree)
        goto out;

    ocfs2_insert_refcount_tree(osb, new);

    tree = new;
    new = NULL;

out:
    *ret_tree = tree;

    osb->osb_ref_tree_lru = tree;

    spin_unlock(&osb->osb_lock);

    if (new)
        ocfs2_free_refcount_tree(new);

    brelse(ref_root_bh);
    return ret;
}

static int ocfs2_get_refcount_block(struct inode *inode, u64 *ref_blkno)
{
    int ret;
    struct buffer_head *di_bh = NULL;
    struct ocfs2_dinode *di;

    ret = ocfs2_read_inode_block(inode, &di_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    BUG_ON(!(OCFS2_I(inode)->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

    di = (struct ocfs2_dinode *)di_bh->b_data;
    *ref_blkno = le64_to_cpu(di->i_refcount_loc);
    brelse(di_bh);
out:
    return ret;
}

static int __ocfs2_lock_refcount_tree(struct ocfs2_super *osb,
                      struct ocfs2_refcount_tree *tree, int rw)
{
    int ret;

    ret = ocfs2_refcount_lock(tree, rw);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (rw)
        down_write(&tree->rf_sem);
    else
        down_read(&tree->rf_sem);

out:
    return ret;
}

/*
 * Lock the refcount tree pointed by ref_blkno and return the tree.
 * In most case, we lock the tree and read the refcount block.
 * So read it here if the caller really needs it.
 *
 * If the tree has been re-created by other node, it will free the
 * old one and re-create it.
 */
int ocfs2_lock_refcount_tree(struct ocfs2_super *osb,
                 u64 ref_blkno, int rw,
                 struct ocfs2_refcount_tree **ret_tree,
                 struct buffer_head **ref_bh)
{
    int ret, delete_tree = 0;
    struct ocfs2_refcount_tree *tree = NULL;
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_block *rb;

again:
    ret = ocfs2_get_refcount_tree(osb, ref_blkno, &tree);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    ocfs2_refcount_tree_get(tree);

    ret = __ocfs2_lock_refcount_tree(osb, tree, rw);
    if (ret) {
        mlog_errno(ret);
        ocfs2_refcount_tree_put(tree);
        goto out;
    }

    ret = ocfs2_read_refcount_block(&tree->rf_ci, tree->rf_blkno,
                    &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        ocfs2_unlock_refcount_tree(osb, tree, rw);
        ocfs2_refcount_tree_put(tree);
        goto out;
    }

    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    /*
     * If the refcount block has been freed and re-created, we may need
     * to recreate the refcount tree also.
     *
     * Here we just remove the tree from the rb-tree, and the last
     * kref holder will unlock and delete this refcount_tree.
     * Then we goto "again" and ocfs2_get_refcount_tree will create
     * the new refcount tree for us.
     */
    if (tree->rf_generation != le32_to_cpu(rb->rf_generation)) {
        if (!tree->rf_removed) {
            ocfs2_erase_refcount_tree_from_list(osb, tree);
            tree->rf_removed = 1;
            delete_tree = 1;
        }

        ocfs2_unlock_refcount_tree(osb, tree, rw);
        /*
         * We get an extra reference when we create the refcount
         * tree, so another put will destroy it.
         */
        if (delete_tree)
            ocfs2_refcount_tree_put(tree);
        brelse(ref_root_bh);
        ref_root_bh = NULL;
        goto again;
    }

    *ret_tree = tree;
    if (ref_bh) {
        *ref_bh = ref_root_bh;
        ref_root_bh = NULL;
    }
out:
    brelse(ref_root_bh);
    return ret;
}

void ocfs2_unlock_refcount_tree(struct ocfs2_super *osb,
                struct ocfs2_refcount_tree *tree, int rw)
{
    if (rw)
        up_write(&tree->rf_sem);
    else
        up_read(&tree->rf_sem);

    ocfs2_refcount_unlock(tree, rw);
    ocfs2_refcount_tree_put(tree);
}

void ocfs2_purge_refcount_trees(struct ocfs2_super *osb)
{
    struct rb_node *node;
    struct ocfs2_refcount_tree *tree;
    struct rb_root *root = &osb->osb_rf_lock_tree;

    while ((node = rb_last(root)) != NULL) {
        tree = rb_entry(node, struct ocfs2_refcount_tree, rf_node);

        trace_ocfs2_purge_refcount_trees(
                (unsigned long long) tree->rf_blkno);

        rb_erase(&tree->rf_node, root);
        ocfs2_free_refcount_tree(tree);
    }
}

/*
 * Create a refcount tree for an inode.
 * We take for granted that the inode is already locked.
 */
static int ocfs2_create_refcount_tree(struct inode *inode,
                      struct buffer_head *di_bh)
{
    int ret;
    handle_t *handle = NULL;
    struct ocfs2_alloc_context *meta_ac = NULL;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct buffer_head *new_bh = NULL;
    struct ocfs2_refcount_block *rb;
    struct ocfs2_refcount_tree *new_tree = NULL, *tree = NULL;
    u16 suballoc_bit_start;
    u32 num_got;
    u64 suballoc_loc, first_blkno;

    BUG_ON(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL);

    trace_ocfs2_create_refcount_tree(
        (unsigned long long)OCFS2_I(inode)->ip_blkno);

    ret = ocfs2_reserve_new_metadata_blocks(osb, 1, &meta_ac);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    handle = ocfs2_start_trans(osb, OCFS2_REFCOUNT_TREE_CREATE_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;
    }

    ret = ocfs2_claim_metadata(handle, meta_ac, 1, &suballoc_loc,
                   &suballoc_bit_start, &num_got,
                   &first_blkno);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    new_tree = ocfs2_allocate_refcount_tree(osb, first_blkno);
    if (!new_tree) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out_commit;
    }

    new_bh = sb_getblk(inode->i_sb, first_blkno);
    ocfs2_set_new_buffer_uptodate(&new_tree->rf_ci, new_bh);

    ret = ocfs2_journal_access_rb(handle, &new_tree->rf_ci, new_bh,
                      OCFS2_JOURNAL_ACCESS_CREATE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    /* Initialize ocfs2_refcount_block. */
    rb = (struct ocfs2_refcount_block *)new_bh->b_data;
    memset(rb, 0, inode->i_sb->s_blocksize);
    strcpy((void *)rb, OCFS2_REFCOUNT_BLOCK_SIGNATURE);
    rb->rf_suballoc_slot = cpu_to_le16(meta_ac->ac_alloc_slot);
    rb->rf_suballoc_loc = cpu_to_le64(suballoc_loc);
    rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
    rb->rf_fs_generation = cpu_to_le32(osb->fs_generation);
    rb->rf_blkno = cpu_to_le64(first_blkno);
    rb->rf_count = cpu_to_le32(1);
    rb->rf_records.rl_count =
            cpu_to_le16(ocfs2_refcount_recs_per_rb(osb->sb));
    spin_lock(&osb->osb_lock);
    rb->rf_generation = osb->s_next_generation++;
    spin_unlock(&osb->osb_lock);

    ocfs2_journal_dirty(handle, new_bh);

    spin_lock(&oi->ip_lock);
    oi->ip_dyn_features |= OCFS2_HAS_REFCOUNT_FL;
    di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
    di->i_refcount_loc = cpu_to_le64(first_blkno);
    spin_unlock(&oi->ip_lock);

    trace_ocfs2_create_refcount_tree_blkno((unsigned long long)first_blkno);

    ocfs2_journal_dirty(handle, di_bh);

    /*
     * We have to init the tree lock here since it will use
     * the generation number to create it.
     */
    new_tree->rf_generation = le32_to_cpu(rb->rf_generation);
    ocfs2_init_refcount_tree_lock(osb, new_tree, first_blkno,
                      new_tree->rf_generation);

    spin_lock(&osb->osb_lock);
    tree = ocfs2_find_refcount_tree(osb, first_blkno);

    /*
     * We've just created a new refcount tree in this block.  If
     * we found a refcount tree on the ocfs2_super, it must be
     * one we just deleted.  We free the old tree before
     * inserting the new tree.
     */
    BUG_ON(tree && tree->rf_generation == new_tree->rf_generation);
    if (tree)
        ocfs2_erase_refcount_tree_from_list_no_lock(osb, tree);
    ocfs2_insert_refcount_tree(osb, new_tree);
    spin_unlock(&osb->osb_lock);
    new_tree = NULL;
    if (tree)
        ocfs2_refcount_tree_put(tree);

out_commit:
    ocfs2_commit_trans(osb, handle);

out:
    if (new_tree) {
        ocfs2_metadata_cache_exit(&new_tree->rf_ci);
        kfree(new_tree);
    }

    brelse(new_bh);
    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);

    return ret;
}

static int ocfs2_set_refcount_tree(struct inode *inode,
                   struct buffer_head *di_bh,
                   u64 refcount_loc)
{
    int ret;
    handle_t *handle = NULL;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_block *rb;
    struct ocfs2_refcount_tree *ref_tree;

    BUG_ON(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL);

    ret = ocfs2_lock_refcount_tree(osb, refcount_loc, 1,
                       &ref_tree, &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    handle = ocfs2_start_trans(osb, OCFS2_REFCOUNT_TREE_SET_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;
    }

    ret = ocfs2_journal_access_rb(handle, &ref_tree->rf_ci, ref_root_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    le32_add_cpu(&rb->rf_count, 1);

    ocfs2_journal_dirty(handle, ref_root_bh);

    spin_lock(&oi->ip_lock);
    oi->ip_dyn_features |= OCFS2_HAS_REFCOUNT_FL;
    di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
    di->i_refcount_loc = cpu_to_le64(refcount_loc);
    spin_unlock(&oi->ip_lock);
    ocfs2_journal_dirty(handle, di_bh);

out_commit:
    ocfs2_commit_trans(osb, handle);
out:
    ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
    brelse(ref_root_bh);

    return ret;
}

int ocfs2_remove_refcount_tree(struct inode *inode, struct buffer_head *di_bh)
{
    int ret, delete_tree = 0;
    handle_t *handle = NULL;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_refcount_block *rb;
    struct inode *alloc_inode = NULL;
    struct buffer_head *alloc_bh = NULL;
    struct buffer_head *blk_bh = NULL;
    struct ocfs2_refcount_tree *ref_tree;
    int credits = OCFS2_REFCOUNT_TREE_REMOVE_CREDITS;
    u64 blk = 0, bg_blkno = 0, ref_blkno = le64_to_cpu(di->i_refcount_loc);
    u16 bit = 0;

    if (!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL))
        return 0;

    BUG_ON(!ref_blkno);
    ret = ocfs2_lock_refcount_tree(osb, ref_blkno, 1, &ref_tree, &blk_bh);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    rb = (struct ocfs2_refcount_block *)blk_bh->b_data;

    /*
     * If we are the last user, we need to free the block.
     * So lock the allocator ahead.
     */
    if (le32_to_cpu(rb->rf_count) == 1) {
        blk = le64_to_cpu(rb->rf_blkno);
        bit = le16_to_cpu(rb->rf_suballoc_bit);
        if (rb->rf_suballoc_loc)
            bg_blkno = le64_to_cpu(rb->rf_suballoc_loc);
        else
            bg_blkno = ocfs2_which_suballoc_group(blk, bit);

        alloc_inode = ocfs2_get_system_file_inode(osb,
                    EXTENT_ALLOC_SYSTEM_INODE,
                    le16_to_cpu(rb->rf_suballoc_slot));
        if (!alloc_inode) {
            ret = -ENOMEM;
            mlog_errno(ret);
            goto out;
        }
        mutex_lock(&alloc_inode->i_mutex);

        ret = ocfs2_inode_lock(alloc_inode, &alloc_bh, 1);
        if (ret) {
            mlog_errno(ret);
            goto out_mutex;
        }

        credits += OCFS2_SUBALLOC_FREE;
    }

    handle = ocfs2_start_trans(osb, credits);
    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;
    }

    ret = ocfs2_journal_access_rb(handle, &ref_tree->rf_ci, blk_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    spin_lock(&oi->ip_lock);
    oi->ip_dyn_features &= ~OCFS2_HAS_REFCOUNT_FL;
    di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
    di->i_refcount_loc = 0;
    spin_unlock(&oi->ip_lock);
    ocfs2_journal_dirty(handle, di_bh);

    le32_add_cpu(&rb->rf_count , -1);
    ocfs2_journal_dirty(handle, blk_bh);

    if (!rb->rf_count) {
        delete_tree = 1;
        ocfs2_erase_refcount_tree_from_list(osb, ref_tree);
        ret = ocfs2_free_suballoc_bits(handle, alloc_inode,
                           alloc_bh, bit, bg_blkno, 1);
        if (ret)
            mlog_errno(ret);
    }

out_commit:
    ocfs2_commit_trans(osb, handle);
out_unlock:
    if (alloc_inode) {
        ocfs2_inode_unlock(alloc_inode, 1);
        brelse(alloc_bh);
    }
out_mutex:
    if (alloc_inode) {
        mutex_unlock(&alloc_inode->i_mutex);
        iput(alloc_inode);
    }
out:
    ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
    if (delete_tree)
        ocfs2_refcount_tree_put(ref_tree);
    brelse(blk_bh);

    return ret;
}

static void ocfs2_find_refcount_rec_in_rl(struct ocfs2_caching_info *ci,
                      struct buffer_head *ref_leaf_bh,
                      u64 cpos, unsigned int len,
                      struct ocfs2_refcount_rec *ret_rec,
                      int *index)
{
    int i = 0;
    struct ocfs2_refcount_block *rb =
        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_rec *rec = NULL;

    for (; i < le16_to_cpu(rb->rf_records.rl_used); i++) {
        rec = &rb->rf_records.rl_recs[i];

        if (le64_to_cpu(rec->r_cpos) +
            le32_to_cpu(rec->r_clusters) <= cpos)
            continue;
        else if (le64_to_cpu(rec->r_cpos) > cpos)
            break;

        /* ok, cpos fail in this rec. Just return. */
        if (ret_rec)
            *ret_rec = *rec;
        goto out;
    }

    if (ret_rec) {
        /* We meet with a hole here, so fake the rec. */
        ret_rec->r_cpos = cpu_to_le64(cpos);
        ret_rec->r_refcount = 0;
        if (i < le16_to_cpu(rb->rf_records.rl_used) &&
            le64_to_cpu(rec->r_cpos) < cpos + len)
            ret_rec->r_clusters =
                cpu_to_le32(le64_to_cpu(rec->r_cpos) - cpos);
        else
            ret_rec->r_clusters = cpu_to_le32(len);
    }

out:
    *index = i;
}

/*
 * Try to remove refcount tree. The mechanism is:
 * 1) Check whether i_clusters == 0, if no, exit.
 * 2) check whether we have i_xattr_loc in dinode. if yes, exit.
 * 3) Check whether we have inline xattr stored outside, if yes, exit.
 * 4) Remove the tree.
 */
int ocfs2_try_remove_refcount_tree(struct inode *inode,
                   struct buffer_head *di_bh)
{
    int ret;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;

    down_write(&oi->ip_xattr_sem);
    down_write(&oi->ip_alloc_sem);

    if (oi->ip_clusters)
        goto out;

    if ((oi->ip_dyn_features & OCFS2_HAS_XATTR_FL) && di->i_xattr_loc)
        goto out;

    if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL &&
        ocfs2_has_inline_xattr_value_outside(inode, di))
        goto out;

    ret = ocfs2_remove_refcount_tree(inode, di_bh);
    if (ret)
        mlog_errno(ret);
out:
    up_write(&oi->ip_alloc_sem);
    up_write(&oi->ip_xattr_sem);
    return 0;
}

/*
 * Find the end range for a leaf refcount block indicated by
 * el->l_recs[index].e_blkno.
 */
static int ocfs2_get_refcount_cpos_end(struct ocfs2_caching_info *ci,
                       struct buffer_head *ref_root_bh,
                       struct ocfs2_extent_block *eb,
                       struct ocfs2_extent_list *el,
                       int index,  u32 *cpos_end)
{
    int ret, i, subtree_root;
    u32 cpos;
    u64 blkno;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct ocfs2_path *left_path = NULL, *right_path = NULL;
    struct ocfs2_extent_tree et;
    struct ocfs2_extent_list *tmp_el;

    if (index < le16_to_cpu(el->l_next_free_rec) - 1) {
        /*
         * We have a extent rec after index, so just use the e_cpos
         * of the next extent rec.
         */
        *cpos_end = le32_to_cpu(el->l_recs[index+1].e_cpos);
        return 0;
    }

    if (!eb || (eb && !eb->h_next_leaf_blk)) {
        /*
         * We are the last extent rec, so any high cpos should
         * be stored in this leaf refcount block.
         */
        *cpos_end = UINT_MAX;
        return 0;
    }

    /*
     * If the extent block isn't the last one, we have to find
     * the subtree root between this extent block and the next
     * leaf extent block and get the corresponding e_cpos from
     * the subroot. Otherwise we may corrupt the b-tree.
     */
    ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);

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

    cpos = le32_to_cpu(eb->h_list.l_recs[index].e_cpos);
    ret = ocfs2_find_path(ci, left_path, cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

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

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

    ret = ocfs2_find_path(ci, right_path, cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    subtree_root = ocfs2_find_subtree_root(&et, left_path,
                           right_path);

    tmp_el = left_path->p_node[subtree_root].el;
    blkno = left_path->p_node[subtree_root+1].bh->b_blocknr;
    for (i = 0; i < le16_to_cpu(tmp_el->l_next_free_rec); i++) {
        if (le64_to_cpu(tmp_el->l_recs[i].e_blkno) == blkno) {
            *cpos_end = le32_to_cpu(tmp_el->l_recs[i+1].e_cpos);
            break;
        }
    }

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

out:
    ocfs2_free_path(left_path);
    ocfs2_free_path(right_path);
    return ret;
}

/*
 * Given a cpos and len, try to find the refcount record which contains cpos.
 * 1. If cpos can be found in one refcount record, return the record.
 * 2. If cpos can't be found, return a fake record which start from cpos
 *    and end at a small value between cpos+len and start of the next record.
 *    This fake record has r_refcount = 0.
 */
static int ocfs2_get_refcount_rec(struct ocfs2_caching_info *ci,
                  struct buffer_head *ref_root_bh,
                  u64 cpos, unsigned int len,
                  struct ocfs2_refcount_rec *ret_rec,
                  int *index,
                  struct buffer_head **ret_bh)
{
    int ret = 0, i, found;
    u32 low_cpos, uninitialized_var(cpos_end);
    struct ocfs2_extent_list *el;
    struct ocfs2_extent_rec *rec = NULL;
    struct ocfs2_extent_block *eb = NULL;
    struct buffer_head *eb_bh = NULL, *ref_leaf_bh = NULL;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_root_bh->b_data;

    if (!(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL)) {
        ocfs2_find_refcount_rec_in_rl(ci, ref_root_bh, cpos, len,
                          ret_rec, index);
        *ret_bh = ref_root_bh;
        get_bh(ref_root_bh);
        return 0;
    }

    el = &rb->rf_list;
    low_cpos = cpos & OCFS2_32BIT_POS_MASK;

    if (el->l_tree_depth) {
        ret = ocfs2_find_leaf(ci, el, low_cpos, &eb_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

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

        if (el->l_tree_depth) {
            ocfs2_error(sb,
            "refcount tree %llu has non zero tree "
            "depth in leaf btree tree block %llu\n",
            (unsigned long long)ocfs2_metadata_cache_owner(ci),
            (unsigned long long)eb_bh->b_blocknr);
            ret = -EROFS;
            goto out;
        }
    }

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

        if (le32_to_cpu(rec->e_cpos) <= low_cpos) {
            found = 1;
            break;
        }
    }

    if (found) {
        ret = ocfs2_get_refcount_cpos_end(ci, ref_root_bh,
                          eb, el, i, &cpos_end);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (cpos_end < low_cpos + len)
            len = cpos_end - low_cpos;
    }

    ret = ocfs2_read_refcount_block(ci, le64_to_cpu(rec->e_blkno),
                    &ref_leaf_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_find_refcount_rec_in_rl(ci, ref_leaf_bh, cpos, len,
                      ret_rec, index);
    *ret_bh = ref_leaf_bh;
out:
    brelse(eb_bh);
    return ret;
}

enum ocfs2_ref_rec_contig {
    REF_CONTIG_NONE = 0,
    REF_CONTIG_LEFT,
    REF_CONTIG_RIGHT,
    REF_CONTIG_LEFTRIGHT,
};

static enum ocfs2_ref_rec_contig
    ocfs2_refcount_rec_adjacent(struct ocfs2_refcount_block *rb,
                    int index)
{
    if ((rb->rf_records.rl_recs[index].r_refcount ==
        rb->rf_records.rl_recs[index + 1].r_refcount) &&
        (le64_to_cpu(rb->rf_records.rl_recs[index].r_cpos) +
        le32_to_cpu(rb->rf_records.rl_recs[index].r_clusters) ==
        le64_to_cpu(rb->rf_records.rl_recs[index + 1].r_cpos)))
        return REF_CONTIG_RIGHT;

    return REF_CONTIG_NONE;
}

static enum ocfs2_ref_rec_contig
    ocfs2_refcount_rec_contig(struct ocfs2_refcount_block *rb,
                  int index)
{
    enum ocfs2_ref_rec_contig ret = REF_CONTIG_NONE;

    if (index < le16_to_cpu(rb->rf_records.rl_used) - 1)
        ret = ocfs2_refcount_rec_adjacent(rb, index);

    if (index > 0) {
        enum ocfs2_ref_rec_contig tmp;

        tmp = ocfs2_refcount_rec_adjacent(rb, index - 1);

        if (tmp == REF_CONTIG_RIGHT) {
            if (ret == REF_CONTIG_RIGHT)
                ret = REF_CONTIG_LEFTRIGHT;
            else
                ret = REF_CONTIG_LEFT;
        }
    }

    return ret;
}

static void ocfs2_rotate_refcount_rec_left(struct ocfs2_refcount_block *rb,
                       int index)
{
    BUG_ON(rb->rf_records.rl_recs[index].r_refcount !=
           rb->rf_records.rl_recs[index+1].r_refcount);

    le32_add_cpu(&rb->rf_records.rl_recs[index].r_clusters,
             le32_to_cpu(rb->rf_records.rl_recs[index+1].r_clusters));

    if (index < le16_to_cpu(rb->rf_records.rl_used) - 2)
        memmove(&rb->rf_records.rl_recs[index + 1],
            &rb->rf_records.rl_recs[index + 2],
            sizeof(struct ocfs2_refcount_rec) *
            (le16_to_cpu(rb->rf_records.rl_used) - index - 2));

    memset(&rb->rf_records.rl_recs[le16_to_cpu(rb->rf_records.rl_used) - 1],
           0, sizeof(struct ocfs2_refcount_rec));
    le16_add_cpu(&rb->rf_records.rl_used, -1);
}

/*
 * Merge the refcount rec if we are contiguous with the adjacent recs.
 */
static void ocfs2_refcount_rec_merge(struct ocfs2_refcount_block *rb,
                     int index)
{
    enum ocfs2_ref_rec_contig contig =
                ocfs2_refcount_rec_contig(rb, index);

    if (contig == REF_CONTIG_NONE)
        return;

    if (contig == REF_CONTIG_LEFT || contig == REF_CONTIG_LEFTRIGHT) {
        BUG_ON(index == 0);
        index--;
    }

    ocfs2_rotate_refcount_rec_left(rb, index);

    if (contig == REF_CONTIG_LEFTRIGHT)
        ocfs2_rotate_refcount_rec_left(rb, index);
}

/*
 * Change the refcount indexed by "index" in ref_bh.
 * If refcount reaches 0, remove it.
 */
static int ocfs2_change_refcount_rec(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_leaf_bh,
                     int index, int merge, int change)
{
    int ret;
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_list *rl = &rb->rf_records;
    struct ocfs2_refcount_rec *rec = &rl->rl_recs[index];

    ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_change_refcount_rec(
        (unsigned long long)ocfs2_metadata_cache_owner(ci),
        index, le32_to_cpu(rec->r_refcount), change);
    le32_add_cpu(&rec->r_refcount, change);

    if (!rec->r_refcount) {
        if (index != le16_to_cpu(rl->rl_used) - 1) {
            memmove(rec, rec + 1,
                (le16_to_cpu(rl->rl_used) - index - 1) *
                sizeof(struct ocfs2_refcount_rec));
            memset(&rl->rl_recs[le16_to_cpu(rl->rl_used) - 1],
                   0, sizeof(struct ocfs2_refcount_rec));
        }

        le16_add_cpu(&rl->rl_used, -1);
    } else if (merge)
        ocfs2_refcount_rec_merge(rb, index);

    ocfs2_journal_dirty(handle, ref_leaf_bh);
out:
    return ret;
}

static int ocfs2_expand_inline_ref_root(handle_t *handle,
                    struct ocfs2_caching_info *ci,
                    struct buffer_head *ref_root_bh,
                    struct buffer_head **ref_leaf_bh,
                    struct ocfs2_alloc_context *meta_ac)
{
    int ret;
    u16 suballoc_bit_start;
    u32 num_got;
    u64 suballoc_loc, blkno;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct buffer_head *new_bh = NULL;
    struct ocfs2_refcount_block *new_rb;
    struct ocfs2_refcount_block *root_rb =
            (struct ocfs2_refcount_block *)ref_root_bh->b_data;

    ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_claim_metadata(handle, meta_ac, 1, &suballoc_loc,
                   &suballoc_bit_start, &num_got,
                   &blkno);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    new_bh = sb_getblk(sb, blkno);
    if (new_bh == NULL) {
        ret = -EIO;
        mlog_errno(ret);
        goto out;
    }
    ocfs2_set_new_buffer_uptodate(ci, new_bh);

    ret = ocfs2_journal_access_rb(handle, ci, new_bh,
                      OCFS2_JOURNAL_ACCESS_CREATE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * Initialize ocfs2_refcount_block.
     * It should contain the same information as the old root.
     * so just memcpy it and change the corresponding field.
     */
    memcpy(new_bh->b_data, ref_root_bh->b_data, sb->s_blocksize);

    new_rb = (struct ocfs2_refcount_block *)new_bh->b_data;
    new_rb->rf_suballoc_slot = cpu_to_le16(meta_ac->ac_alloc_slot);
    new_rb->rf_suballoc_loc = cpu_to_le64(suballoc_loc);
    new_rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
    new_rb->rf_blkno = cpu_to_le64(blkno);
    new_rb->rf_cpos = cpu_to_le32(0);
    new_rb->rf_parent = cpu_to_le64(ref_root_bh->b_blocknr);
    new_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_LEAF_FL);
    ocfs2_journal_dirty(handle, new_bh);

    /* Now change the root. */
    memset(&root_rb->rf_list, 0, sb->s_blocksize -
           offsetof(struct ocfs2_refcount_block, rf_list));
    root_rb->rf_list.l_count = cpu_to_le16(ocfs2_extent_recs_per_rb(sb));
    root_rb->rf_clusters = cpu_to_le32(1);
    root_rb->rf_list.l_next_free_rec = cpu_to_le16(1);
    root_rb->rf_list.l_recs[0].e_blkno = cpu_to_le64(blkno);
    root_rb->rf_list.l_recs[0].e_leaf_clusters = cpu_to_le16(1);
    root_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_TREE_FL);

    ocfs2_journal_dirty(handle, ref_root_bh);

    trace_ocfs2_expand_inline_ref_root((unsigned long long)blkno,
        le16_to_cpu(new_rb->rf_records.rl_used));

    *ref_leaf_bh = new_bh;
    new_bh = NULL;
out:
    brelse(new_bh);
    return ret;
}

static int ocfs2_refcount_rec_no_intersect(struct ocfs2_refcount_rec *prev,
                       struct ocfs2_refcount_rec *next)
{
    if (ocfs2_get_ref_rec_low_cpos(prev) + le32_to_cpu(prev->r_clusters) <=
        ocfs2_get_ref_rec_low_cpos(next))
        return 1;

    return 0;
}

static int cmp_refcount_rec_by_low_cpos(const void *a, const void *b)
{
    const struct ocfs2_refcount_rec *l = a, *r = b;
    u32 l_cpos = ocfs2_get_ref_rec_low_cpos(l);
    u32 r_cpos = ocfs2_get_ref_rec_low_cpos(r);

    if (l_cpos > r_cpos)
        return 1;
    if (l_cpos < r_cpos)
        return -1;
    return 0;
}

static int cmp_refcount_rec_by_cpos(const void *a, const void *b)
{
    const struct ocfs2_refcount_rec *l = a, *r = b;
    u64 l_cpos = le64_to_cpu(l->r_cpos);
    u64 r_cpos = le64_to_cpu(r->r_cpos);

    if (l_cpos > r_cpos)
        return 1;
    if (l_cpos < r_cpos)
        return -1;
    return 0;
}

static void swap_refcount_rec(void *a, void *b, int size)
{
    struct ocfs2_refcount_rec *l = a, *r = b, tmp;

    tmp = *(struct ocfs2_refcount_rec *)l;
    *(struct ocfs2_refcount_rec *)l =
            *(struct ocfs2_refcount_rec *)r;
    *(struct ocfs2_refcount_rec *)r = tmp;
}

/*
 * The refcount cpos are ordered by their 64bit cpos,
 * But we will use the low 32 bit to be the e_cpos in the b-tree.
 * So we need to make sure that this pos isn't intersected with others.
 *
 * Note: The refcount block is already sorted by their low 32 bit cpos,
 *       So just try the middle pos first, and we will exit when we find
 *       the good position.
 */
static int ocfs2_find_refcount_split_pos(struct ocfs2_refcount_list *rl,
                     u32 *split_pos, int *split_index)
{
    int num_used = le16_to_cpu(rl->rl_used);
    int delta, middle = num_used / 2;

    for (delta = 0; delta < middle; delta++) {
        /* Let's check delta earlier than middle */
        if (ocfs2_refcount_rec_no_intersect(
                    &rl->rl_recs[middle - delta - 1],
                    &rl->rl_recs[middle - delta])) {
            *split_index = middle - delta;
            break;
        }

        /* For even counts, don't walk off the end */
        if ((middle + delta + 1) == num_used)
            continue;

        /* Now try delta past middle */
        if (ocfs2_refcount_rec_no_intersect(
                    &rl->rl_recs[middle + delta],
                    &rl->rl_recs[middle + delta + 1])) {
            *split_index = middle + delta + 1;
            break;
        }
    }

    if (delta >= middle)
        return -ENOSPC;

    *split_pos = ocfs2_get_ref_rec_low_cpos(&rl->rl_recs[*split_index]);
    return 0;
}

static int ocfs2_divide_leaf_refcount_block(struct buffer_head *ref_leaf_bh,
                        struct buffer_head *new_bh,
                        u32 *split_cpos)
{
    int split_index = 0, num_moved, ret;
    u32 cpos = 0;
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_list *rl = &rb->rf_records;
    struct ocfs2_refcount_block *new_rb =
            (struct ocfs2_refcount_block *)new_bh->b_data;
    struct ocfs2_refcount_list *new_rl = &new_rb->rf_records;

    trace_ocfs2_divide_leaf_refcount_block(
        (unsigned long long)ref_leaf_bh->b_blocknr,
        le16_to_cpu(rl->rl_count), le16_to_cpu(rl->rl_used));

    /*
     * XXX: Improvement later.
     * If we know all the high 32 bit cpos is the same, no need to sort.
     *
     * In order to make the whole process safe, we do:
     * 1. sort the entries by their low 32 bit cpos first so that we can
     *    find the split cpos easily.
     * 2. call ocfs2_insert_extent to insert the new refcount block.
     * 3. move the refcount rec to the new block.
     * 4. sort the entries by their 64 bit cpos.
     * 5. dirty the new_rb and rb.
     */
    sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
         sizeof(struct ocfs2_refcount_rec),
         cmp_refcount_rec_by_low_cpos, swap_refcount_rec);

    ret = ocfs2_find_refcount_split_pos(rl, &cpos, &split_index);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    new_rb->rf_cpos = cpu_to_le32(cpos);

    /* move refcount records starting from split_index to the new block. */
    num_moved = le16_to_cpu(rl->rl_used) - split_index;
    memcpy(new_rl->rl_recs, &rl->rl_recs[split_index],
           num_moved * sizeof(struct ocfs2_refcount_rec));

    /*ok, remove the entries we just moved over to the other block. */
    memset(&rl->rl_recs[split_index], 0,
           num_moved * sizeof(struct ocfs2_refcount_rec));

    /* change old and new rl_used accordingly. */
    le16_add_cpu(&rl->rl_used, -num_moved);
    new_rl->rl_used = cpu_to_le16(num_moved);

    sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
         sizeof(struct ocfs2_refcount_rec),
         cmp_refcount_rec_by_cpos, swap_refcount_rec);

    sort(&new_rl->rl_recs, le16_to_cpu(new_rl->rl_used),
         sizeof(struct ocfs2_refcount_rec),
         cmp_refcount_rec_by_cpos, swap_refcount_rec);

    *split_cpos = cpos;
    return 0;
}

static int ocfs2_new_leaf_refcount_block(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_root_bh,
                     struct buffer_head *ref_leaf_bh,
                     struct ocfs2_alloc_context *meta_ac)
{
    int ret;
    u16 suballoc_bit_start;
    u32 num_got, new_cpos;
    u64 suballoc_loc, blkno;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct ocfs2_refcount_block *root_rb =
            (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    struct buffer_head *new_bh = NULL;
    struct ocfs2_refcount_block *new_rb;
    struct ocfs2_extent_tree ref_et;

    BUG_ON(!(le32_to_cpu(root_rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL));

    ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_claim_metadata(handle, meta_ac, 1, &suballoc_loc,
                   &suballoc_bit_start, &num_got,
                   &blkno);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    new_bh = sb_getblk(sb, blkno);
    if (new_bh == NULL) {
        ret = -EIO;
        mlog_errno(ret);
        goto out;
    }
    ocfs2_set_new_buffer_uptodate(ci, new_bh);

    ret = ocfs2_journal_access_rb(handle, ci, new_bh,
                      OCFS2_JOURNAL_ACCESS_CREATE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /* Initialize ocfs2_refcount_block. */
    new_rb = (struct ocfs2_refcount_block *)new_bh->b_data;
    memset(new_rb, 0, sb->s_blocksize);
    strcpy((void *)new_rb, OCFS2_REFCOUNT_BLOCK_SIGNATURE);
    new_rb->rf_suballoc_slot = cpu_to_le16(meta_ac->ac_alloc_slot);
    new_rb->rf_suballoc_loc = cpu_to_le64(suballoc_loc);
    new_rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
    new_rb->rf_fs_generation = cpu_to_le32(OCFS2_SB(sb)->fs_generation);
    new_rb->rf_blkno = cpu_to_le64(blkno);
    new_rb->rf_parent = cpu_to_le64(ref_root_bh->b_blocknr);
    new_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_LEAF_FL);
    new_rb->rf_records.rl_count =
                cpu_to_le16(ocfs2_refcount_recs_per_rb(sb));
    new_rb->rf_generation = root_rb->rf_generation;

    ret = ocfs2_divide_leaf_refcount_block(ref_leaf_bh, new_bh, &new_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_journal_dirty(handle, ref_leaf_bh);
    ocfs2_journal_dirty(handle, new_bh);

    ocfs2_init_refcount_extent_tree(&ref_et, ci, ref_root_bh);

    trace_ocfs2_new_leaf_refcount_block(
            (unsigned long long)new_bh->b_blocknr, new_cpos);

    /* Insert the new leaf block with the specific offset cpos. */
    ret = ocfs2_insert_extent(handle, &ref_et, new_cpos, new_bh->b_blocknr,
                  1, 0, meta_ac);
    if (ret)
        mlog_errno(ret);

out:
    brelse(new_bh);
    return ret;
}

static int ocfs2_expand_refcount_tree(handle_t *handle,
                      struct ocfs2_caching_info *ci,
                      struct buffer_head *ref_root_bh,
                      struct buffer_head *ref_leaf_bh,
                      struct ocfs2_alloc_context *meta_ac)
{
    int ret;
    struct buffer_head *expand_bh = NULL;

    if (ref_root_bh == ref_leaf_bh) {
        /*
         * the old root bh hasn't been expanded to a b-tree,
         * so expand it first.
         */
        ret = ocfs2_expand_inline_ref_root(handle, ci, ref_root_bh,
                           &expand_bh, meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    } else {
        expand_bh = ref_leaf_bh;
        get_bh(expand_bh);
    }


    /* Now add a new refcount block into the tree.*/
    ret = ocfs2_new_leaf_refcount_block(handle, ci, ref_root_bh,
                        expand_bh, meta_ac);
    if (ret)
        mlog_errno(ret);
out:
    brelse(expand_bh);
    return ret;
}

/*
 * Adjust the extent rec in b-tree representing ref_leaf_bh.
 *
 * Only called when we have inserted a new refcount rec at index 0
 * which means ocfs2_extent_rec.e_cpos may need some change.
 */
static int ocfs2_adjust_refcount_rec(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_root_bh,
                     struct buffer_head *ref_leaf_bh,
                     struct ocfs2_refcount_rec *rec)
{
    int ret = 0, i;
    u32 new_cpos, old_cpos;
    struct ocfs2_path *path = NULL;
    struct ocfs2_extent_tree et;
    struct ocfs2_refcount_block *rb =
        (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    struct ocfs2_extent_list *el;

    if (!(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL))
        goto out;

    rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    old_cpos = le32_to_cpu(rb->rf_cpos);
    new_cpos = le64_to_cpu(rec->r_cpos) & OCFS2_32BIT_POS_MASK;
    if (old_cpos <= new_cpos)
        goto out;

    ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);

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

    ret = ocfs2_find_path(ci, path, old_cpos);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * 2 more credits, one for the leaf refcount block, one for
     * the extent block contains the extent rec.
     */
    ret = ocfs2_extend_trans(handle, 2);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_eb(handle, ci, path_leaf_bh(path),
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

    /* change the leaf extent block first. */
    el = path_leaf_el(path);

    for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++)
        if (le32_to_cpu(el->l_recs[i].e_cpos) == old_cpos)
            break;

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

    el->l_recs[i].e_cpos = cpu_to_le32(new_cpos);

    /* change the r_cpos in the leaf block. */
    rb->rf_cpos = cpu_to_le32(new_cpos);

    ocfs2_journal_dirty(handle, path_leaf_bh(path));
    ocfs2_journal_dirty(handle, ref_leaf_bh);

out:
    ocfs2_free_path(path);
    return ret;
}

static int ocfs2_insert_refcount_rec(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_root_bh,
                     struct buffer_head *ref_leaf_bh,
                     struct ocfs2_refcount_rec *rec,
                     int index, int merge,
                     struct ocfs2_alloc_context *meta_ac)
{
    int ret;
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_list *rf_list = &rb->rf_records;
    struct buffer_head *new_bh = NULL;

    BUG_ON(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL);

    if (rf_list->rl_used == rf_list->rl_count) {
        u64 cpos = le64_to_cpu(rec->r_cpos);
        u32 len = le32_to_cpu(rec->r_clusters);

        ret = ocfs2_expand_refcount_tree(handle, ci, ref_root_bh,
                         ref_leaf_bh, meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                         cpos, len, NULL, &index,
                         &new_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ref_leaf_bh = new_bh;
        rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        rf_list = &rb->rf_records;
    }

    ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (index < le16_to_cpu(rf_list->rl_used))
        memmove(&rf_list->rl_recs[index + 1],
            &rf_list->rl_recs[index],
            (le16_to_cpu(rf_list->rl_used) - index) *
             sizeof(struct ocfs2_refcount_rec));

    trace_ocfs2_insert_refcount_rec(
        (unsigned long long)ref_leaf_bh->b_blocknr, index,
        (unsigned long long)le64_to_cpu(rec->r_cpos),
        le32_to_cpu(rec->r_clusters), le32_to_cpu(rec->r_refcount));

    rf_list->rl_recs[index] = *rec;

    le16_add_cpu(&rf_list->rl_used, 1);

    if (merge)
        ocfs2_refcount_rec_merge(rb, index);

    ocfs2_journal_dirty(handle, ref_leaf_bh);

    if (index == 0) {
        ret = ocfs2_adjust_refcount_rec(handle, ci,
                        ref_root_bh,
                        ref_leaf_bh, rec);
        if (ret)
            mlog_errno(ret);
    }
out:
    brelse(new_bh);
    return ret;
}

/*
 * Split the refcount_rec indexed by "index" in ref_leaf_bh.
 * This is much simple than our b-tree code.
 * split_rec is the new refcount rec we want to insert.
 * If split_rec->r_refcount > 0, we are changing the refcount(in case we
 * increase refcount or decrease a refcount to non-zero).
 * If split_rec->r_refcount == 0, we are punching a hole in current refcount
 * rec( in case we decrease a refcount to zero).
 */
static int ocfs2_split_refcount_rec(handle_t *handle,
                    struct ocfs2_caching_info *ci,
                    struct buffer_head *ref_root_bh,
                    struct buffer_head *ref_leaf_bh,
                    struct ocfs2_refcount_rec *split_rec,
                    int index, int merge,
                    struct ocfs2_alloc_context *meta_ac,
                    struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret, recs_need;
    u32 len;
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_list *rf_list = &rb->rf_records;
    struct ocfs2_refcount_rec *orig_rec = &rf_list->rl_recs[index];
    struct ocfs2_refcount_rec *tail_rec = NULL;
    struct buffer_head *new_bh = NULL;

    BUG_ON(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL);

    trace_ocfs2_split_refcount_rec(le64_to_cpu(orig_rec->r_cpos),
        le32_to_cpu(orig_rec->r_clusters),
        le32_to_cpu(orig_rec->r_refcount),
        le64_to_cpu(split_rec->r_cpos),
        le32_to_cpu(split_rec->r_clusters),
        le32_to_cpu(split_rec->r_refcount));

    /*
     * If we just need to split the header or tail clusters,
     * no more recs are needed, just split is OK.
     * Otherwise we at least need one new recs.
     */
    if (!split_rec->r_refcount &&
        (split_rec->r_cpos == orig_rec->r_cpos ||
         le64_to_cpu(split_rec->r_cpos) +
         le32_to_cpu(split_rec->r_clusters) ==
         le64_to_cpu(orig_rec->r_cpos) + le32_to_cpu(orig_rec->r_clusters)))
        recs_need = 0;
    else
        recs_need = 1;

    /*
     * We need one more rec if we split in the middle and the new rec have
     * some refcount in it.
     */
    if (split_rec->r_refcount &&
        (split_rec->r_cpos != orig_rec->r_cpos &&
         le64_to_cpu(split_rec->r_cpos) +
         le32_to_cpu(split_rec->r_clusters) !=
         le64_to_cpu(orig_rec->r_cpos) + le32_to_cpu(orig_rec->r_clusters)))
        recs_need++;

    /* If the leaf block don't have enough record, expand it. */
    if (le16_to_cpu(rf_list->rl_used) + recs_need >
                     le16_to_cpu(rf_list->rl_count)) {
        struct ocfs2_refcount_rec tmp_rec;
        u64 cpos = le64_to_cpu(orig_rec->r_cpos);
        len = le32_to_cpu(orig_rec->r_clusters);
        ret = ocfs2_expand_refcount_tree(handle, ci, ref_root_bh,
                         ref_leaf_bh, meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        /*
         * We have to re-get it since now cpos may be moved to
         * another leaf block.
         */
        ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                         cpos, len, &tmp_rec, &index,
                         &new_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        ref_leaf_bh = new_bh;
        rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        rf_list = &rb->rf_records;
        orig_rec = &rf_list->rl_recs[index];
    }

    ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * We have calculated out how many new records we need and store
     * in recs_need, so spare enough space first by moving the records
     * after "index" to the end.
     */
    if (index != le16_to_cpu(rf_list->rl_used) - 1)
        memmove(&rf_list->rl_recs[index + 1 + recs_need],
            &rf_list->rl_recs[index + 1],
            (le16_to_cpu(rf_list->rl_used) - index - 1) *
             sizeof(struct ocfs2_refcount_rec));

    len = (le64_to_cpu(orig_rec->r_cpos) +
          le32_to_cpu(orig_rec->r_clusters)) -
          (le64_to_cpu(split_rec->r_cpos) +
          le32_to_cpu(split_rec->r_clusters));

    /*
     * If we have "len", the we will split in the tail and move it
     * to the end of the space we have just spared.
     */
    if (len) {
        tail_rec = &rf_list->rl_recs[index + recs_need];

        memcpy(tail_rec, orig_rec, sizeof(struct ocfs2_refcount_rec));
        le64_add_cpu(&tail_rec->r_cpos,
                 le32_to_cpu(tail_rec->r_clusters) - len);
        tail_rec->r_clusters = cpu_to_le32(len);
    }

    /*
     * If the split pos isn't the same as the original one, we need to
     * split in the head.
     *
     * Note: We have the chance that split_rec.r_refcount = 0,
     * recs_need = 0 and len > 0, which means we just cut the head from
     * the orig_rec and in that case we have done some modification in
     * orig_rec above, so the check for r_cpos is faked.
     */
    if (split_rec->r_cpos != orig_rec->r_cpos && tail_rec != orig_rec) {
        len = le64_to_cpu(split_rec->r_cpos) -
              le64_to_cpu(orig_rec->r_cpos);
        orig_rec->r_clusters = cpu_to_le32(len);
        index++;
    }

    le16_add_cpu(&rf_list->rl_used, recs_need);

    if (split_rec->r_refcount) {
        rf_list->rl_recs[index] = *split_rec;
        trace_ocfs2_split_refcount_rec_insert(
            (unsigned long long)ref_leaf_bh->b_blocknr, index,
            (unsigned long long)le64_to_cpu(split_rec->r_cpos),
            le32_to_cpu(split_rec->r_clusters),
            le32_to_cpu(split_rec->r_refcount));

        if (merge)
            ocfs2_refcount_rec_merge(rb, index);
    }

    ocfs2_journal_dirty(handle, ref_leaf_bh);

out:
    brelse(new_bh);
    return ret;
}

static int __ocfs2_increase_refcount(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_root_bh,
                     u64 cpos, u32 len, int merge,
                     struct ocfs2_alloc_context *meta_ac,
                     struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret = 0, index;
    struct buffer_head *ref_leaf_bh = NULL;
    struct ocfs2_refcount_rec rec;
    unsigned int set_len = 0;

    trace_ocfs2_increase_refcount_begin(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)cpos, len);

    while (len) {
        ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                         cpos, len, &rec, &index,
                         &ref_leaf_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        set_len = le32_to_cpu(rec.r_clusters);

        /*
         * Here we may meet with 3 situations:
         *
         * 1. If we find an already existing record, and the length
         *    is the same, cool, we just need to increase the r_refcount
         *    and it is OK.
         * 2. If we find a hole, just insert it with r_refcount = 1.
         * 3. If we are in the middle of one extent record, split
         *    it.
         */
        if (rec.r_refcount && le64_to_cpu(rec.r_cpos) == cpos &&
            set_len <= len) {
            trace_ocfs2_increase_refcount_change(
                (unsigned long long)cpos, set_len,
                le32_to_cpu(rec.r_refcount));
            ret = ocfs2_change_refcount_rec(handle, ci,
                            ref_leaf_bh, index,
                            merge, 1);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        } else if (!rec.r_refcount) {
            rec.r_refcount = cpu_to_le32(1);

            trace_ocfs2_increase_refcount_insert(
                 (unsigned long long)le64_to_cpu(rec.r_cpos),
                 set_len);
            ret = ocfs2_insert_refcount_rec(handle, ci, ref_root_bh,
                            ref_leaf_bh,
                            &rec, index,
                            merge, meta_ac);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        } else  {
            set_len = min((u64)(cpos + len),
                      le64_to_cpu(rec.r_cpos) + set_len) - cpos;
            rec.r_cpos = cpu_to_le64(cpos);
            rec.r_clusters = cpu_to_le32(set_len);
            le32_add_cpu(&rec.r_refcount, 1);

            trace_ocfs2_increase_refcount_split(
                 (unsigned long long)le64_to_cpu(rec.r_cpos),
                 set_len, le32_to_cpu(rec.r_refcount));
            ret = ocfs2_split_refcount_rec(handle, ci,
                               ref_root_bh, ref_leaf_bh,
                               &rec, index, merge,
                               meta_ac, dealloc);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }

        cpos += set_len;
        len -= set_len;
        brelse(ref_leaf_bh);
        ref_leaf_bh = NULL;
    }

out:
    brelse(ref_leaf_bh);
    return ret;
}

static int ocfs2_remove_refcount_extent(handle_t *handle,
                struct ocfs2_caching_info *ci,
                struct buffer_head *ref_root_bh,
                struct buffer_head *ref_leaf_bh,
                struct ocfs2_alloc_context *meta_ac,
                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_extent_tree et;

    BUG_ON(rb->rf_records.rl_used);

    trace_ocfs2_remove_refcount_extent(
        (unsigned long long)ocfs2_metadata_cache_owner(ci),
        (unsigned long long)ref_leaf_bh->b_blocknr,
        le32_to_cpu(rb->rf_cpos));

    ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);
    ret = ocfs2_remove_extent(handle, &et, le32_to_cpu(rb->rf_cpos),
                  1, meta_ac, dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_remove_from_cache(ci, ref_leaf_bh);

    /*
     * add the freed block to the dealloc so that it will be freed
     * when we run dealloc.
     */
    ret = ocfs2_cache_block_dealloc(dealloc, EXTENT_ALLOC_SYSTEM_INODE,
                    le16_to_cpu(rb->rf_suballoc_slot),
                    le64_to_cpu(rb->rf_suballoc_loc),
                    le64_to_cpu(rb->rf_blkno),
                    le16_to_cpu(rb->rf_suballoc_bit));
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;

    le32_add_cpu(&rb->rf_clusters, -1);

    /*
     * check whether we need to restore the root refcount block if
     * there is no leaf extent block at atll.
     */
    if (!rb->rf_list.l_next_free_rec) {
        BUG_ON(rb->rf_clusters);

        trace_ocfs2_restore_refcount_block(
             (unsigned long long)ref_root_bh->b_blocknr);

        rb->rf_flags = 0;
        rb->rf_parent = 0;
        rb->rf_cpos = 0;
        memset(&rb->rf_records, 0, sb->s_blocksize -
               offsetof(struct ocfs2_refcount_block, rf_records));
        rb->rf_records.rl_count =
                cpu_to_le16(ocfs2_refcount_recs_per_rb(sb));
    }

    ocfs2_journal_dirty(handle, ref_root_bh);

out:
    return ret;
}

int ocfs2_increase_refcount(handle_t *handle,
                struct ocfs2_caching_info *ci,
                struct buffer_head *ref_root_bh,
                u64 cpos, u32 len,
                struct ocfs2_alloc_context *meta_ac,
                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    return __ocfs2_increase_refcount(handle, ci, ref_root_bh,
                     cpos, len, 1,
                     meta_ac, dealloc);
}

static int ocfs2_decrease_refcount_rec(handle_t *handle,
                struct ocfs2_caching_info *ci,
                struct buffer_head *ref_root_bh,
                struct buffer_head *ref_leaf_bh,
                int index, u64 cpos, unsigned int len,
                struct ocfs2_alloc_context *meta_ac,
                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret;
    struct ocfs2_refcount_block *rb =
            (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
    struct ocfs2_refcount_rec *rec = &rb->rf_records.rl_recs[index];

    BUG_ON(cpos < le64_to_cpu(rec->r_cpos));
    BUG_ON(cpos + len >
           le64_to_cpu(rec->r_cpos) + le32_to_cpu(rec->r_clusters));

    trace_ocfs2_decrease_refcount_rec(
        (unsigned long long)ocfs2_metadata_cache_owner(ci),
        (unsigned long long)cpos, len);

    if (cpos == le64_to_cpu(rec->r_cpos) &&
        len == le32_to_cpu(rec->r_clusters))
        ret = ocfs2_change_refcount_rec(handle, ci,
                        ref_leaf_bh, index, 1, -1);
    else {
        struct ocfs2_refcount_rec split = *rec;
        split.r_cpos = cpu_to_le64(cpos);
        split.r_clusters = cpu_to_le32(len);

        le32_add_cpu(&split.r_refcount, -1);

        ret = ocfs2_split_refcount_rec(handle, ci,
                           ref_root_bh, ref_leaf_bh,
                           &split, index, 1,
                           meta_ac, dealloc);
    }

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

    /* Remove the leaf refcount block if it contains no refcount record. */
    if (!rb->rf_records.rl_used && ref_leaf_bh != ref_root_bh) {
        ret = ocfs2_remove_refcount_extent(handle, ci, ref_root_bh,
                           ref_leaf_bh, meta_ac,
                           dealloc);
        if (ret)
            mlog_errno(ret);
    }

out:
    return ret;
}

static int __ocfs2_decrease_refcount(handle_t *handle,
                     struct ocfs2_caching_info *ci,
                     struct buffer_head *ref_root_bh,
                     u64 cpos, u32 len,
                     struct ocfs2_alloc_context *meta_ac,
                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                     int delete)
{
    int ret = 0, index = 0;
    struct ocfs2_refcount_rec rec;
    unsigned int r_count = 0, r_len;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    struct buffer_head *ref_leaf_bh = NULL;

    trace_ocfs2_decrease_refcount(
        (unsigned long long)ocfs2_metadata_cache_owner(ci),
        (unsigned long long)cpos, len, delete);

    while (len) {
        ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                         cpos, len, &rec, &index,
                         &ref_leaf_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        r_count = le32_to_cpu(rec.r_refcount);
        BUG_ON(r_count == 0);
        if (!delete)
            BUG_ON(r_count > 1);

        r_len = min((u64)(cpos + len), le64_to_cpu(rec.r_cpos) +
                  le32_to_cpu(rec.r_clusters)) - cpos;

        ret = ocfs2_decrease_refcount_rec(handle, ci, ref_root_bh,
                          ref_leaf_bh, index,
                          cpos, r_len,
                          meta_ac, dealloc);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (le32_to_cpu(rec.r_refcount) == 1 && delete) {
            ret = ocfs2_cache_cluster_dealloc(dealloc,
                      ocfs2_clusters_to_blocks(sb, cpos),
                              r_len);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }

        cpos += r_len;
        len -= r_len;
        brelse(ref_leaf_bh);
        ref_leaf_bh = NULL;
    }

out:
    brelse(ref_leaf_bh);
    return ret;
}

/* Caller must hold refcount tree lock. */
int ocfs2_decrease_refcount(struct inode *inode,
                handle_t *handle, u32 cpos, u32 len,
                struct ocfs2_alloc_context *meta_ac,
                struct ocfs2_cached_dealloc_ctxt *dealloc,
                int delete)
{
    int ret;
    u64 ref_blkno;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_tree *tree;

    BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

    ret = ocfs2_get_refcount_block(inode, &ref_blkno);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_get_refcount_tree(OCFS2_SB(inode->i_sb), ref_blkno, &tree);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_read_refcount_block(&tree->rf_ci, tree->rf_blkno,
                    &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = __ocfs2_decrease_refcount(handle, &tree->rf_ci, ref_root_bh,
                    cpos, len, meta_ac, dealloc, delete);
    if (ret)
        mlog_errno(ret);
out:
    brelse(ref_root_bh);
    return ret;
}

/*
 * Mark the already-existing extent at cpos as refcounted for len clusters.
 * This adds the refcount 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.
 */
static int ocfs2_mark_extent_refcounted(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_refcounted(OCFS2_I(inode)->ip_blkno,
                       cpos, len, phys);

    if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
        ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                "tree, but the feature bit is not set in the "
                "super block.", inode->i_ino);
        ret = -EROFS;
        goto out;
    }

    ret = ocfs2_change_extent_flag(handle, et, cpos,
                       len, phys, meta_ac, dealloc,
                       OCFS2_EXT_REFCOUNTED, 0);
    if (ret)
        mlog_errno(ret);

out:
    return ret;
}

/*
 * Given some contiguous physical clusters, calculate what we need
 * for modifying their refcount.
 */
static int ocfs2_calc_refcount_meta_credits(struct super_block *sb,
                        struct ocfs2_caching_info *ci,
                        struct buffer_head *ref_root_bh,
                        u64 start_cpos,
                        u32 clusters,
                        int *meta_add,
                        int *credits)
{
    int ret = 0, index, ref_blocks = 0, recs_add = 0;
    u64 cpos = start_cpos;
    struct ocfs2_refcount_block *rb;
    struct ocfs2_refcount_rec rec;
    struct buffer_head *ref_leaf_bh = NULL, *prev_bh = NULL;
    u32 len;

    while (clusters) {
        ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                         cpos, clusters, &rec,
                         &index, &ref_leaf_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (ref_leaf_bh != prev_bh) {
            /*
             * Now we encounter a new leaf block, so calculate
             * whether we need to extend the old leaf.
             */
            if (prev_bh) {
                rb = (struct ocfs2_refcount_block *)
                            prev_bh->b_data;

                if (le16_to_cpu(rb->rf_records.rl_used) +
                    recs_add >
                    le16_to_cpu(rb->rf_records.rl_count))
                    ref_blocks++;
            }

            recs_add = 0;
            *credits += 1;
            brelse(prev_bh);
            prev_bh = ref_leaf_bh;
            get_bh(prev_bh);
        }

        rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;

        trace_ocfs2_calc_refcount_meta_credits_iterate(
                recs_add, (unsigned long long)cpos, clusters,
                (unsigned long long)le64_to_cpu(rec.r_cpos),
                le32_to_cpu(rec.r_clusters),
                le32_to_cpu(rec.r_refcount), index);

        len = min((u64)cpos + clusters, le64_to_cpu(rec.r_cpos) +
              le32_to_cpu(rec.r_clusters)) - cpos;
        /*
         * We record all the records which will be inserted to the
         * same refcount block, so that we can tell exactly whether
         * we need a new refcount block or not.
         *
         * If we will insert a new one, this is easy and only happens
         * during adding refcounted flag to the extent, so we don't
         * have a chance of spliting. We just need one record.
         *
         * If the refcount rec already exists, that would be a little
         * complicated. we may have to:
         * 1) split at the beginning if the start pos isn't aligned.
         *    we need 1 more record in this case.
         * 2) split int the end if the end pos isn't aligned.
         *    we need 1 more record in this case.
         * 3) split in the middle because of file system fragmentation.
         *    we need 2 more records in this case(we can't detect this
         *    beforehand, so always think of the worst case).
         */
        if (rec.r_refcount) {
            recs_add += 2;
            /* Check whether we need a split at the beginning. */
            if (cpos == start_cpos &&
                cpos != le64_to_cpu(rec.r_cpos))
                recs_add++;

            /* Check whether we need a split in the end. */
            if (cpos + clusters < le64_to_cpu(rec.r_cpos) +
                le32_to_cpu(rec.r_clusters))
                recs_add++;
        } else
            recs_add++;

        brelse(ref_leaf_bh);
        ref_leaf_bh = NULL;
        clusters -= len;
        cpos += len;
    }

    if (prev_bh) {
        rb = (struct ocfs2_refcount_block *)prev_bh->b_data;

        if (le16_to_cpu(rb->rf_records.rl_used) + recs_add >
            le16_to_cpu(rb->rf_records.rl_count))
            ref_blocks++;

        *credits += 1;
    }

    if (!ref_blocks)
        goto out;

    *meta_add += ref_blocks;
    *credits += ref_blocks;

    /*
     * So we may need ref_blocks to insert into the tree.
     * That also means we need to change the b-tree and add that number
     * of records since we never merge them.
     * We need one more block for expansion since the new created leaf
     * block is also full and needs split.
     */
    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    if (le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL) {
        struct ocfs2_extent_tree et;

        ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);
        *meta_add += ocfs2_extend_meta_needed(et.et_root_el);
        *credits += ocfs2_calc_extend_credits(sb,
                              et.et_root_el,
                              ref_blocks);
    } else {
        *credits += OCFS2_EXPAND_REFCOUNT_TREE_CREDITS;
        *meta_add += 1;
    }

out:

    trace_ocfs2_calc_refcount_meta_credits(
        (unsigned long long)start_cpos, clusters,
        *meta_add, *credits);
    brelse(ref_leaf_bh);
    brelse(prev_bh);
    return ret;
}

/*
 * For refcount tree, we will decrease some contiguous clusters
 * refcount count, so just go through it to see how many blocks
 * we gonna touch and whether we need to create new blocks.
 *
 * Normally the refcount blocks store these refcount should be
 * contiguous also, so that we can get the number easily.
 * We will at most add split 2 refcount records and 2 more
 * refcount blocks, so just check it in a rough way.
 *
 * Caller must hold refcount tree lock.
 */
int ocfs2_prepare_refcount_change_for_del(struct inode *inode,
                      u64 refcount_loc,
                      u64 phys_blkno,
                      u32 clusters,
                      int *credits,
                      int *ref_blocks)
{
    int ret;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_tree *tree;
    u64 start_cpos = ocfs2_blocks_to_clusters(inode->i_sb, phys_blkno);

    if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
        ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                "tree, but the feature bit is not set in the "
                "super block.", inode->i_ino);
        ret = -EROFS;
        goto out;
    }

    BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

    ret = ocfs2_get_refcount_tree(OCFS2_SB(inode->i_sb),
                      refcount_loc, &tree);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_read_refcount_block(&tree->rf_ci, refcount_loc,
                    &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_calc_refcount_meta_credits(inode->i_sb,
                           &tree->rf_ci,
                           ref_root_bh,
                           start_cpos, clusters,
                           ref_blocks, credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_prepare_refcount_change_for_del(*ref_blocks, *credits);

out:
    brelse(ref_root_bh);
    return ret;
}

#define MAX_CONTIG_BYTES    1048576

static inline unsigned int ocfs2_cow_contig_clusters(struct super_block *sb)
{
    return ocfs2_clusters_for_bytes(sb, MAX_CONTIG_BYTES);
}

static inline unsigned int ocfs2_cow_contig_mask(struct super_block *sb)
{
    return ~(ocfs2_cow_contig_clusters(sb) - 1);
}

/*
 * Given an extent that starts at 'start' and an I/O that starts at 'cpos',
 * find an offset (start + (n * contig_clusters)) that is closest to cpos
 * while still being less than or equal to it.
 *
 * The goal is to break the extent at a multiple of contig_clusters.
 */
static inline unsigned int ocfs2_cow_align_start(struct super_block *sb,
                         unsigned int start,
                         unsigned int cpos)
{
    BUG_ON(start > cpos);

    return start + ((cpos - start) & ocfs2_cow_contig_mask(sb));
}

/*
 * Given a cluster count of len, pad it out so that it is a multiple
 * of contig_clusters.
 */
static inline unsigned int ocfs2_cow_align_length(struct super_block *sb,
                          unsigned int len)
{
    unsigned int padded =
        (len + (ocfs2_cow_contig_clusters(sb) - 1)) &
        ocfs2_cow_contig_mask(sb);

    /* Did we wrap? */
    if (padded < len)
        padded = UINT_MAX;

    return padded;
}

/*
 * Calculate out the start and number of virtual clusters we need to to CoW.
 *
 * cpos is vitual start cluster position we want to do CoW in a
 * file and write_len is the cluster length.
 * max_cpos is the place where we want to stop CoW intentionally.
 *
 * Normal we will start CoW from the beginning of extent record cotaining cpos.
 * We try to break up extents on boundaries of MAX_CONTIG_BYTES so that we
 * get good I/O from the resulting extent tree.
 */
static int ocfs2_refcount_cal_cow_clusters(struct inode *inode,
                       struct ocfs2_extent_list *el,
                       u32 cpos,
                       u32 write_len,
                       u32 max_cpos,
                       u32 *cow_start,
                       u32 *cow_len)
{
    int ret = 0;
    int tree_height = le16_to_cpu(el->l_tree_depth), i;
    struct buffer_head *eb_bh = NULL;
    struct ocfs2_extent_block *eb = NULL;
    struct ocfs2_extent_rec *rec;
    unsigned int want_clusters, rec_end = 0;
    int contig_clusters = ocfs2_cow_contig_clusters(inode->i_sb);
    int leaf_clusters;

    BUG_ON(cpos + write_len > max_cpos);

    if (tree_height > 0) {
        ret = ocfs2_find_leaf(INODE_CACHE(inode), el, cpos, &eb_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

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

        if (el->l_tree_depth) {
            ocfs2_error(inode->i_sb,
                    "Inode %lu has non zero tree depth in "
                    "leaf block %llu\n", inode->i_ino,
                    (unsigned long long)eb_bh->b_blocknr);
            ret = -EROFS;
            goto out;
        }
    }

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

        if (ocfs2_is_empty_extent(rec)) {
            mlog_bug_on_msg(i != 0, "Inode %lu has empty record in "
                    "index %d\n", inode->i_ino, i);
            continue;
        }

        if (le32_to_cpu(rec->e_cpos) +
            le16_to_cpu(rec->e_leaf_clusters) <= cpos)
            continue;

        if (*cow_len == 0) {
            /*
             * We should find a refcounted record in the
             * first pass.
             */
            BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED));
            *cow_start = le32_to_cpu(rec->e_cpos);
        }

        /*
         * If we encounter a hole, a non-refcounted record or
         * pass the max_cpos, stop the search.
         */
        if ((!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) ||
            (*cow_len && rec_end != le32_to_cpu(rec->e_cpos)) ||
            (max_cpos <= le32_to_cpu(rec->e_cpos)))
            break;

        leaf_clusters = le16_to_cpu(rec->e_leaf_clusters);
        rec_end = le32_to_cpu(rec->e_cpos) + leaf_clusters;
        if (rec_end > max_cpos) {
            rec_end = max_cpos;
            leaf_clusters = rec_end - le32_to_cpu(rec->e_cpos);
        }

        /*
         * How many clusters do we actually need from
         * this extent?  First we see how many we actually
         * need to complete the write.  If that's smaller
         * than contig_clusters, we try for contig_clusters.
         */
        if (!*cow_len)
            want_clusters = write_len;
        else
            want_clusters = (cpos + write_len) -
                (*cow_start + *cow_len);
        if (want_clusters < contig_clusters)
            want_clusters = contig_clusters;

        /*
         * If the write does not cover the whole extent, we
         * need to calculate how we're going to split the extent.
         * We try to do it on contig_clusters boundaries.
         *
         * Any extent smaller than contig_clusters will be
         * CoWed in its entirety.
         */
        if (leaf_clusters <= contig_clusters)
            *cow_len += leaf_clusters;
        else if (*cow_len || (*cow_start == cpos)) {
            /*
             * This extent needs to be CoW'd from its
             * beginning, so all we have to do is compute
             * how many clusters to grab.  We align
             * want_clusters to the edge of contig_clusters
             * to get better I/O.
             */
            want_clusters = ocfs2_cow_align_length(inode->i_sb,
                                   want_clusters);

            if (leaf_clusters < want_clusters)
                *cow_len += leaf_clusters;
            else
                *cow_len += want_clusters;
        } else if ((*cow_start + contig_clusters) >=
               (cpos + write_len)) {
            /*
             * Breaking off contig_clusters at the front
             * of the extent will cover our write.  That's
             * easy.
             */
            *cow_len = contig_clusters;
        } else if ((rec_end - cpos) <= contig_clusters) {
            /*
             * Breaking off contig_clusters at the tail of
             * this extent will cover cpos.
             */
            *cow_start = rec_end - contig_clusters;
            *cow_len = contig_clusters;
        } else if ((rec_end - cpos) <= want_clusters) {
            /*
             * While we can't fit the entire write in this
             * extent, we know that the write goes from cpos
             * to the end of the extent.  Break that off.
             * We try to break it at some multiple of
             * contig_clusters from the front of the extent.
             * Failing that (ie, cpos is within
             * contig_clusters of the front), we'll CoW the
             * entire extent.
             */
            *cow_start = ocfs2_cow_align_start(inode->i_sb,
                               *cow_start, cpos);
            *cow_len = rec_end - *cow_start;
        } else {
            /*
             * Ok, the entire write lives in the middle of
             * this extent.  Let's try to slice the extent up
             * nicely.  Optimally, our CoW region starts at
             * m*contig_clusters from the beginning of the
             * extent and goes for n*contig_clusters,
             * covering the entire write.
             */
            *cow_start = ocfs2_cow_align_start(inode->i_sb,
                               *cow_start, cpos);

            want_clusters = (cpos + write_len) - *cow_start;
            want_clusters = ocfs2_cow_align_length(inode->i_sb,
                                   want_clusters);
            if (*cow_start + want_clusters <= rec_end)
                *cow_len = want_clusters;
            else
                *cow_len = rec_end - *cow_start;
        }

        /* Have we covered our entire write yet? */
        if ((*cow_start + *cow_len) >= (cpos + write_len))
            break;

        /*
         * If we reach the end of the extent block and don't get enough
         * clusters, continue with the next extent block if possible.
         */
        if (i + 1 == le16_to_cpu(el->l_next_free_rec) &&
            eb && eb->h_next_leaf_blk) {
            brelse(eb_bh);
            eb_bh = NULL;

            ret = ocfs2_read_extent_block(INODE_CACHE(inode),
                           le64_to_cpu(eb->h_next_leaf_blk),
                           &eb_bh);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            eb = (struct ocfs2_extent_block *) eb_bh->b_data;
            el = &eb->h_list;
            i = -1;
        }
    }

out:
    brelse(eb_bh);
    return ret;
}

/*
 * Prepare meta_ac, data_ac and calculate credits when we want to add some
 * num_clusters in data_tree "et" and change the refcount for the old
 * clusters(starting form p_cluster) in the refcount tree.
 *
 * Note:
 * 1. since we may split the old tree, so we at most will need num_clusters + 2
 *    more new leaf records.
 * 2. In some case, we may not need to reserve new clusters(e.g, reflink), so
 *    just give data_ac = NULL.
 */
static int ocfs2_lock_refcount_allocators(struct super_block *sb,
                    u32 p_cluster, u32 num_clusters,
                    struct ocfs2_extent_tree *et,
                    struct ocfs2_caching_info *ref_ci,
                    struct buffer_head *ref_root_bh,
                    struct ocfs2_alloc_context **meta_ac,
                    struct ocfs2_alloc_context **data_ac,
                    int *credits)
{
    int ret = 0, meta_add = 0;
    int num_free_extents = ocfs2_num_free_extents(OCFS2_SB(sb), et);

    if (num_free_extents < 0) {
        ret = num_free_extents;
        mlog_errno(ret);
        goto out;
    }

    if (num_free_extents < num_clusters + 2)
        meta_add =
            ocfs2_extend_meta_needed(et->et_root_el);

    *credits += ocfs2_calc_extend_credits(sb, et->et_root_el,
                          num_clusters + 2);

    ret = ocfs2_calc_refcount_meta_credits(sb, ref_ci, ref_root_bh,
                           p_cluster, num_clusters,
                           &meta_add, credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_lock_refcount_allocators(meta_add, *credits);
    ret = ocfs2_reserve_new_metadata_blocks(OCFS2_SB(sb), meta_add,
                        meta_ac);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (data_ac) {
        ret = ocfs2_reserve_clusters(OCFS2_SB(sb), num_clusters,
                         data_ac);
        if (ret)
            mlog_errno(ret);
    }

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

    return ret;
}

static int ocfs2_clear_cow_buffer(handle_t *handle, struct buffer_head *bh)
{
    BUG_ON(buffer_dirty(bh));

    clear_buffer_mapped(bh);

    return 0;
}

int ocfs2_duplicate_clusters_by_page(handle_t *handle,
                     struct file *file,
                     u32 cpos, u32 old_cluster,
                     u32 new_cluster, u32 new_len)
{
    int ret = 0, partial;
    struct inode *inode = file->f_path.dentry->d_inode;
    struct ocfs2_caching_info *ci = INODE_CACHE(inode);
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
    u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
    struct page *page;
    pgoff_t page_index;
    unsigned int from, to, readahead_pages;
    loff_t offset, end, map_end;
    struct address_space *mapping = inode->i_mapping;

    trace_ocfs2_duplicate_clusters_by_page(cpos, old_cluster,
                           new_cluster, new_len);

    readahead_pages =
        (ocfs2_cow_contig_clusters(sb) <<
         OCFS2_SB(sb)->s_clustersize_bits) >> PAGE_CACHE_SHIFT;
    offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits;
    end = offset + (new_len << OCFS2_SB(sb)->s_clustersize_bits);
    /*
     * We only duplicate pages until we reach the page contains i_size - 1.
     * So trim 'end' to i_size.
     */
    if (end > i_size_read(inode))
        end = i_size_read(inode);

    while (offset < end) {
        page_index = offset >> PAGE_CACHE_SHIFT;
        map_end = ((loff_t)page_index + 1) << PAGE_CACHE_SHIFT;
        if (map_end > end)
            map_end = end;

        /* from, to is the offset within the page. */
        from = offset & (PAGE_CACHE_SIZE - 1);
        to = PAGE_CACHE_SIZE;
        if (map_end & (PAGE_CACHE_SIZE - 1))
            to = map_end & (PAGE_CACHE_SIZE - 1);

        page = find_or_create_page(mapping, page_index, GFP_NOFS);

        /*
         * In case PAGE_CACHE_SIZE <= CLUSTER_SIZE, This page
         * can't be dirtied before we CoW it out.
         */
        if (PAGE_CACHE_SIZE <= OCFS2_SB(sb)->s_clustersize)
            BUG_ON(PageDirty(page));

        if (PageReadahead(page)) {
            page_cache_async_readahead(mapping,
                           &file->f_ra, file,
                           page, page_index,
                           readahead_pages);
        }

        if (!PageUptodate(page)) {
            ret = block_read_full_page(page, ocfs2_get_block);
            if (ret) {
                mlog_errno(ret);
                goto unlock;
            }
            lock_page(page);
        }

        if (page_has_buffers(page)) {
            ret = walk_page_buffers(handle, page_buffers(page),
                        from, to, &partial,
                        ocfs2_clear_cow_buffer);
            if (ret) {
                mlog_errno(ret);
                goto unlock;
            }
        }

        ocfs2_map_and_dirty_page(inode, handle, from, to,
                     page, 0, &new_block);
        mark_page_accessed(page);
unlock:
        unlock_page(page);
        page_cache_release(page);
        page = NULL;
        offset = map_end;
        if (ret)
            break;
    }

    return ret;
}

int ocfs2_duplicate_clusters_by_jbd(handle_t *handle,
                    struct file *file,
                    u32 cpos, u32 old_cluster,
                    u32 new_cluster, u32 new_len)
{
    int ret = 0;
    struct inode *inode = file->f_path.dentry->d_inode;
    struct super_block *sb = inode->i_sb;
    struct ocfs2_caching_info *ci = INODE_CACHE(inode);
    int i, blocks = ocfs2_clusters_to_blocks(sb, new_len);
    u64 old_block = ocfs2_clusters_to_blocks(sb, old_cluster);
    u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
    struct ocfs2_super *osb = OCFS2_SB(sb);
    struct buffer_head *old_bh = NULL;
    struct buffer_head *new_bh = NULL;

    trace_ocfs2_duplicate_clusters_by_page(cpos, old_cluster,
                           new_cluster, new_len);

    for (i = 0; i < blocks; i++, old_block++, new_block++) {
        new_bh = sb_getblk(osb->sb, new_block);
        if (new_bh == NULL) {
            ret = -EIO;
            mlog_errno(ret);
            break;
        }

        ocfs2_set_new_buffer_uptodate(ci, new_bh);

        ret = ocfs2_read_block(ci, old_block, &old_bh, NULL);
        if (ret) {
            mlog_errno(ret);
            break;
        }

        ret = ocfs2_journal_access(handle, ci, new_bh,
                       OCFS2_JOURNAL_ACCESS_CREATE);
        if (ret) {
            mlog_errno(ret);
            break;
        }

        memcpy(new_bh->b_data, old_bh->b_data, sb->s_blocksize);
        ocfs2_journal_dirty(handle, new_bh);

        brelse(new_bh);
        brelse(old_bh);
        new_bh = NULL;
        old_bh = NULL;
    }

    brelse(new_bh);
    brelse(old_bh);
    return ret;
}

static int ocfs2_clear_ext_refcount(handle_t *handle,
                    struct ocfs2_extent_tree *et,
                    u32 cpos, u32 p_cluster, u32 len,
                    unsigned int ext_flags,
                    struct ocfs2_alloc_context *meta_ac,
                    struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret, index;
    struct ocfs2_extent_rec replace_rec;
    struct ocfs2_path *path = NULL;
    struct ocfs2_extent_list *el;
    struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
    u64 ino = ocfs2_metadata_cache_owner(et->et_ci);

    trace_ocfs2_clear_ext_refcount((unsigned long long)ino,
                       cpos, len, p_cluster, ext_flags);

    memset(&replace_rec, 0, sizeof(replace_rec));
    replace_rec.e_cpos = cpu_to_le32(cpos);
    replace_rec.e_leaf_clusters = cpu_to_le16(len);
    replace_rec.e_blkno = cpu_to_le64(ocfs2_clusters_to_blocks(sb,
                                   p_cluster));
    replace_rec.e_flags = ext_flags;
    replace_rec.e_flags &= ~OCFS2_EXT_REFCOUNTED;

    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(sb,
                "Inode %llu has an extent at cpos %u which can no "
                "longer be found.\n",
                (unsigned long long)ino, cpos);
        ret = -EROFS;
        goto out;
    }

    ret = ocfs2_split_extent(handle, et, path, index,
                 &replace_rec, meta_ac, dealloc);
    if (ret)
        mlog_errno(ret);

out:
    ocfs2_free_path(path);
    return ret;
}

static int ocfs2_replace_clusters(handle_t *handle,
                  struct ocfs2_cow_context *context,
                  u32 cpos, u32 old,
                  u32 new, u32 len,
                  unsigned int ext_flags)
{
    int ret;
    struct ocfs2_caching_info *ci = context->data_et.et_ci;
    u64 ino = ocfs2_metadata_cache_owner(ci);

    trace_ocfs2_replace_clusters((unsigned long long)ino,
                     cpos, old, new, len, ext_flags);

    /*If the old clusters is unwritten, no need to duplicate. */
    if (!(ext_flags & OCFS2_EXT_UNWRITTEN)) {
        ret = context->cow_duplicate_clusters(handle, context->file,
                              cpos, old, new, len);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    ret = ocfs2_clear_ext_refcount(handle, &context->data_et,
                       cpos, new, len, ext_flags,
                       context->meta_ac, &context->dealloc);
    if (ret)
        mlog_errno(ret);
out:
    return ret;
}

int ocfs2_cow_sync_writeback(struct super_block *sb,
                 struct inode *inode,
                 u32 cpos, u32 num_clusters)
{
    int ret = 0;
    loff_t offset, end, map_end;
    pgoff_t page_index;
    struct page *page;

    if (ocfs2_should_order_data(inode))
        return 0;

    offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits;
    end = offset + (num_clusters << OCFS2_SB(sb)->s_clustersize_bits);

    ret = filemap_fdatawrite_range(inode->i_mapping,
                       offset, end - 1);
    if (ret < 0) {
        mlog_errno(ret);
        return ret;
    }

    while (offset < end) {
        page_index = offset >> PAGE_CACHE_SHIFT;
        map_end = ((loff_t)page_index + 1) << PAGE_CACHE_SHIFT;
        if (map_end > end)
            map_end = end;

        page = find_or_create_page(inode->i_mapping,
                       page_index, GFP_NOFS);
        BUG_ON(!page);

        wait_on_page_writeback(page);
        if (PageError(page)) {
            ret = -EIO;
            mlog_errno(ret);
        } else
            mark_page_accessed(page);

        unlock_page(page);
        page_cache_release(page);
        page = NULL;
        offset = map_end;
        if (ret)
            break;
    }

    return ret;
}

static int ocfs2_di_get_clusters(struct ocfs2_cow_context *context,
                 u32 v_cluster, u32 *p_cluster,
                 u32 *num_clusters,
                 unsigned int *extent_flags)
{
    return ocfs2_get_clusters(context->inode, v_cluster, p_cluster,
                  num_clusters, extent_flags);
}

static int ocfs2_make_clusters_writable(struct super_block *sb,
                    struct ocfs2_cow_context *context,
                    u32 cpos, u32 p_cluster,
                    u32 num_clusters, unsigned int e_flags)
{
    int ret, delete, index, credits =  0;
    u32 new_bit, new_len, orig_num_clusters;
    unsigned int set_len;
    struct ocfs2_super *osb = OCFS2_SB(sb);
    handle_t *handle;
    struct buffer_head *ref_leaf_bh = NULL;
    struct ocfs2_caching_info *ref_ci = &context->ref_tree->rf_ci;
    struct ocfs2_refcount_rec rec;

    trace_ocfs2_make_clusters_writable(cpos, p_cluster,
                       num_clusters, e_flags);

    ret = ocfs2_lock_refcount_allocators(sb, p_cluster, num_clusters,
                         &context->data_et,
                         ref_ci,
                         context->ref_root_bh,
                         &context->meta_ac,
                         &context->data_ac, &credits);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    if (context->post_refcount)
        credits += context->post_refcount->credits;

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

    orig_num_clusters = num_clusters;

    while (num_clusters) {
        ret = ocfs2_get_refcount_rec(ref_ci, context->ref_root_bh,
                         p_cluster, num_clusters,
                         &rec, &index, &ref_leaf_bh);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        BUG_ON(!rec.r_refcount);
        set_len = min((u64)p_cluster + num_clusters,
                  le64_to_cpu(rec.r_cpos) +
                  le32_to_cpu(rec.r_clusters)) - p_cluster;

        /*
         * There are many different situation here.
         * 1. If refcount == 1, remove the flag and don't COW.
         * 2. If refcount > 1, allocate clusters.
         *    Here we may not allocate r_len once at a time, so continue
         *    until we reach num_clusters.
         */
        if (le32_to_cpu(rec.r_refcount) == 1) {
            delete = 0;
            ret = ocfs2_clear_ext_refcount(handle,
                               &context->data_et,
                               cpos, p_cluster,
                               set_len, e_flags,
                               context->meta_ac,
                               &context->dealloc);
            if (ret) {
                mlog_errno(ret);
                goto out_commit;
            }
        } else {
            delete = 1;

            ret = __ocfs2_claim_clusters(handle,
                             context->data_ac,
                             1, set_len,
                             &new_bit, &new_len);
            if (ret) {
                mlog_errno(ret);
                goto out_commit;
            }

            ret = ocfs2_replace_clusters(handle, context,
                             cpos, p_cluster, new_bit,
                             new_len, e_flags);
            if (ret) {
                mlog_errno(ret);
                goto out_commit;
            }
            set_len = new_len;
        }

        ret = __ocfs2_decrease_refcount(handle, ref_ci,
                        context->ref_root_bh,
                        p_cluster, set_len,
                        context->meta_ac,
                        &context->dealloc, delete);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }

        cpos += set_len;
        p_cluster += set_len;
        num_clusters -= set_len;
        brelse(ref_leaf_bh);
        ref_leaf_bh = NULL;
    }

    /* handle any post_cow action. */
    if (context->post_refcount && context->post_refcount->func) {
        ret = context->post_refcount->func(context->inode, handle,
                        context->post_refcount->para);
        if (ret) {
            mlog_errno(ret);
            goto out_commit;
        }
    }

    /*
     * Here we should write the new page out first if we are
     * in write-back mode.
     */
    if (context->get_clusters == ocfs2_di_get_clusters) {
        ret = ocfs2_cow_sync_writeback(sb, context->inode, cpos,
                           orig_num_clusters);
        if (ret)
            mlog_errno(ret);
    }

out_commit:
    ocfs2_commit_trans(osb, handle);

out:
    if (context->data_ac) {
        ocfs2_free_alloc_context(context->data_ac);
        context->data_ac = NULL;
    }
    if (context->meta_ac) {
        ocfs2_free_alloc_context(context->meta_ac);
        context->meta_ac = NULL;
    }
    brelse(ref_leaf_bh);

    return ret;
}

static int ocfs2_replace_cow(struct ocfs2_cow_context *context)
{
    int ret = 0;
    struct inode *inode = context->inode;
    u32 cow_start = context->cow_start, cow_len = context->cow_len;
    u32 p_cluster, num_clusters;
    unsigned int ext_flags;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
        ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                "tree, but the feature bit is not set in the "
                "super block.", inode->i_ino);
        return -EROFS;
    }

    ocfs2_init_dealloc_ctxt(&context->dealloc);

    while (cow_len) {
        ret = context->get_clusters(context, cow_start, &p_cluster,
                        &num_clusters, &ext_flags);
        if (ret) {
            mlog_errno(ret);
            break;
        }

        BUG_ON(!(ext_flags & OCFS2_EXT_REFCOUNTED));

        if (cow_len < num_clusters)
            num_clusters = cow_len;

        ret = ocfs2_make_clusters_writable(inode->i_sb, context,
                           cow_start, p_cluster,
                           num_clusters, ext_flags);
        if (ret) {
            mlog_errno(ret);
            break;
        }

        cow_len -= num_clusters;
        cow_start += num_clusters;
    }

    if (ocfs2_dealloc_has_cluster(&context->dealloc)) {
        ocfs2_schedule_truncate_log_flush(osb, 1);
        ocfs2_run_deallocs(osb, &context->dealloc);
    }

    return ret;
}

static void ocfs2_readahead_for_cow(struct inode *inode,
                    struct file *file,
                    u32 start, u32 len)
{
    struct address_space *mapping;
    pgoff_t index;
    unsigned long num_pages;
    int cs_bits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;

    if (!file)
        return;

    mapping = file->f_mapping;
    num_pages = (len << cs_bits) >> PAGE_CACHE_SHIFT;
    if (!num_pages)
        num_pages = 1;

    index = ((loff_t)start << cs_bits) >> PAGE_CACHE_SHIFT;
    page_cache_sync_readahead(mapping, &file->f_ra, file,
                  index, num_pages);
}

/*
 * Starting at cpos, try to CoW write_len clusters.  Don't CoW
 * past max_cpos.  This will stop when it runs into a hole or an
 * unrefcounted extent.
 */
static int ocfs2_refcount_cow_hunk(struct inode *inode,
                   struct file *file,
                   struct buffer_head *di_bh,
                   u32 cpos, u32 write_len, u32 max_cpos)
{
    int ret;
    u32 cow_start = 0, cow_len = 0;
    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 buffer_head *ref_root_bh = NULL;
    struct ocfs2_refcount_tree *ref_tree;
    struct ocfs2_cow_context *context = NULL;

    BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

    ret = ocfs2_refcount_cal_cow_clusters(inode, &di->id2.i_list,
                          cpos, write_len, max_cpos,
                          &cow_start, &cow_len);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_refcount_cow_hunk(OCFS2_I(inode)->ip_blkno,
                      cpos, write_len, max_cpos,
                      cow_start, cow_len);

    BUG_ON(cow_len == 0);

    ocfs2_readahead_for_cow(inode, file, cow_start, cow_len);

    context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
    if (!context) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_lock_refcount_tree(osb, le64_to_cpu(di->i_refcount_loc),
                       1, &ref_tree, &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    context->inode = inode;
    context->cow_start = cow_start;
    context->cow_len = cow_len;
    context->ref_tree = ref_tree;
    context->ref_root_bh = ref_root_bh;
    context->cow_duplicate_clusters = ocfs2_duplicate_clusters_by_page;
    context->get_clusters = ocfs2_di_get_clusters;
    context->file = file;

    ocfs2_init_dinode_extent_tree(&context->data_et,
                      INODE_CACHE(inode), di_bh);

    ret = ocfs2_replace_cow(context);
    if (ret)
        mlog_errno(ret);

    /*
     * truncate the extent map here since no matter whether we meet with
     * any error during the action, we shouldn't trust cached extent map
     * any more.
     */
    ocfs2_extent_map_trunc(inode, cow_start);

    ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
    brelse(ref_root_bh);
out:
    kfree(context);
    return ret;
}

/*
 * CoW any and all clusters between cpos and cpos+write_len.
 * Don't CoW past max_cpos.  If this returns successfully, all
 * clusters between cpos and cpos+write_len are safe to modify.
 */
int ocfs2_refcount_cow(struct inode *inode,
               struct file *file,
               struct buffer_head *di_bh,
               u32 cpos, u32 write_len, u32 max_cpos)
{
    int ret = 0;
    u32 p_cluster, num_clusters;
    unsigned int ext_flags;

    while (write_len) {
        ret = ocfs2_get_clusters(inode, cpos, &p_cluster,
                     &num_clusters, &ext_flags);
        if (ret) {
            mlog_errno(ret);
            break;
        }

        if (write_len < num_clusters)
            num_clusters = write_len;

        if (ext_flags & OCFS2_EXT_REFCOUNTED) {
            ret = ocfs2_refcount_cow_hunk(inode, file, di_bh, cpos,
                              num_clusters, max_cpos);
            if (ret) {
                mlog_errno(ret);
                break;
            }
        }

        write_len -= num_clusters;
        cpos += num_clusters;
    }

    return ret;
}

static int ocfs2_xattr_value_get_clusters(struct ocfs2_cow_context *context,
                      u32 v_cluster, u32 *p_cluster,
                      u32 *num_clusters,
                      unsigned int *extent_flags)
{
    struct inode *inode = context->inode;
    struct ocfs2_xattr_value_root *xv = context->cow_object;

    return ocfs2_xattr_get_clusters(inode, v_cluster, p_cluster,
                    num_clusters, &xv->xr_list,
                    extent_flags);
}

/*
 * Given a xattr value root, calculate the most meta/credits we need for
 * refcount tree change if we truncate it to 0.
 */
int ocfs2_refcounted_xattr_delete_need(struct inode *inode,
                       struct ocfs2_caching_info *ref_ci,
                       struct buffer_head *ref_root_bh,
                       struct ocfs2_xattr_value_root *xv,
                       int *meta_add, int *credits)
{
    int ret = 0, index, ref_blocks = 0;
    u32 p_cluster, num_clusters;
    u32 cpos = 0, clusters = le32_to_cpu(xv->xr_clusters);
    struct ocfs2_refcount_block *rb;
    struct ocfs2_refcount_rec rec;
    struct buffer_head *ref_leaf_bh = NULL;

    while (cpos < clusters) {
        ret = ocfs2_xattr_get_clusters(inode, cpos, &p_cluster,
                           &num_clusters, &xv->xr_list,
                           NULL);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        cpos += num_clusters;

        while (num_clusters) {
            ret = ocfs2_get_refcount_rec(ref_ci, ref_root_bh,
                             p_cluster, num_clusters,
                             &rec, &index,
                             &ref_leaf_bh);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            BUG_ON(!rec.r_refcount);

            rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;

            /*
             * We really don't know whether the other clusters is in
             * this refcount block or not, so just take the worst
             * case that all the clusters are in this block and each
             * one will split a refcount rec, so totally we need
             * clusters * 2 new refcount rec.
             */
            if (le16_to_cpu(rb->rf_records.rl_used) + clusters * 2 >
                le16_to_cpu(rb->rf_records.rl_count))
                ref_blocks++;

            *credits += 1;
            brelse(ref_leaf_bh);
            ref_leaf_bh = NULL;

            if (num_clusters <= le32_to_cpu(rec.r_clusters))
                break;
            else
                num_clusters -= le32_to_cpu(rec.r_clusters);
            p_cluster += num_clusters;
        }
    }

    *meta_add += ref_blocks;
    if (!ref_blocks)
        goto out;

    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
    if (le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL)
        *credits += OCFS2_EXPAND_REFCOUNT_TREE_CREDITS;
    else {
        struct ocfs2_extent_tree et;

        ocfs2_init_refcount_extent_tree(&et, ref_ci, ref_root_bh);
        *credits += ocfs2_calc_extend_credits(inode->i_sb,
                              et.et_root_el,
                              ref_blocks);
    }

out:
    brelse(ref_leaf_bh);
    return ret;
}

/*
 * Do CoW for xattr.
 */
int ocfs2_refcount_cow_xattr(struct inode *inode,
                 struct ocfs2_dinode *di,
                 struct ocfs2_xattr_value_buf *vb,
                 struct ocfs2_refcount_tree *ref_tree,
                 struct buffer_head *ref_root_bh,
                 u32 cpos, u32 write_len,
                 struct ocfs2_post_refcount *post)
{
    int ret;
    struct ocfs2_xattr_value_root *xv = vb->vb_xv;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_cow_context *context = NULL;
    u32 cow_start, cow_len;

    BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

    ret = ocfs2_refcount_cal_cow_clusters(inode, &xv->xr_list,
                          cpos, write_len, UINT_MAX,
                          &cow_start, &cow_len);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    BUG_ON(cow_len == 0);

    context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
    if (!context) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }

    context->inode = inode;
    context->cow_start = cow_start;
    context->cow_len = cow_len;
    context->ref_tree = ref_tree;
    context->ref_root_bh = ref_root_bh;
    context->cow_object = xv;

    context->cow_duplicate_clusters = ocfs2_duplicate_clusters_by_jbd;
    /* We need the extra credits for duplicate_clusters by jbd. */
    context->extra_credits =
        ocfs2_clusters_to_blocks(inode->i_sb, 1) * cow_len;
    context->get_clusters = ocfs2_xattr_value_get_clusters;
    context->post_refcount = post;

    ocfs2_init_xattr_value_extent_tree(&context->data_et,
                       INODE_CACHE(inode), vb);

    ret = ocfs2_replace_cow(context);
    if (ret)
        mlog_errno(ret);

out:
    kfree(context);
    return ret;
}

/*
 * Insert a new extent into refcount tree and mark a extent rec
 * as refcounted in the dinode tree.
 */
int ocfs2_add_refcount_flag(struct inode *inode,
                struct ocfs2_extent_tree *data_et,
                struct ocfs2_caching_info *ref_ci,
                struct buffer_head *ref_root_bh,
                u32 cpos, u32 p_cluster, u32 num_clusters,
                struct ocfs2_cached_dealloc_ctxt *dealloc,
                struct ocfs2_post_refcount *post)
{
    int ret;
    handle_t *handle;
    int credits = 1, ref_blocks = 0;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_alloc_context *meta_ac = NULL;

    ret = ocfs2_calc_refcount_meta_credits(inode->i_sb,
                           ref_ci, ref_root_bh,
                           p_cluster, num_clusters,
                           &ref_blocks, &credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    trace_ocfs2_add_refcount_flag(ref_blocks, credits);

    if (ref_blocks) {
        ret = ocfs2_reserve_new_metadata_blocks(OCFS2_SB(inode->i_sb),
                            ref_blocks, &meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    if (post)
        credits += post->credits;

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

    ret = ocfs2_mark_extent_refcounted(inode, data_et, handle,
                       cpos, num_clusters, p_cluster,
                       meta_ac, dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    ret = __ocfs2_increase_refcount(handle, ref_ci, ref_root_bh,
                    p_cluster, num_clusters, 0,
                    meta_ac, dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    if (post && post->func) {
        ret = post->func(inode, handle, post->para);
        if (ret)
            mlog_errno(ret);
    }

out_commit:
    ocfs2_commit_trans(osb, handle);
out:
    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);
    return ret;
}

static int ocfs2_change_ctime(struct inode *inode,
                  struct buffer_head *di_bh)
{
    int ret;
    handle_t *handle;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;

    handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb),
                   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;
    }

    inode->i_ctime = CURRENT_TIME;
    di->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
    di->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);

    ocfs2_journal_dirty(handle, di_bh);

out_commit:
    ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
out:
    return ret;
}

static int ocfs2_attach_refcount_tree(struct inode *inode,
                      struct buffer_head *di_bh)
{
    int ret, data_changed = 0;
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_refcount_tree *ref_tree;
    unsigned int ext_flags;
    loff_t size;
    u32 cpos, num_clusters, clusters, p_cluster;
    struct ocfs2_cached_dealloc_ctxt dealloc;
    struct ocfs2_extent_tree di_et;

    ocfs2_init_dealloc_ctxt(&dealloc);

    if (!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL)) {
        ret = ocfs2_create_refcount_tree(inode, di_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    BUG_ON(!di->i_refcount_loc);
    ret = ocfs2_lock_refcount_tree(osb,
                       le64_to_cpu(di->i_refcount_loc), 1,
                       &ref_tree, &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
        goto attach_xattr;

    ocfs2_init_dinode_extent_tree(&di_et, INODE_CACHE(inode), di_bh);

    size = i_size_read(inode);
    clusters = ocfs2_clusters_for_bytes(inode->i_sb, size);

    cpos = 0;
    while (cpos < clusters) {
        ret = ocfs2_get_clusters(inode, cpos, &p_cluster,
                     &num_clusters, &ext_flags);

        if (p_cluster && !(ext_flags & OCFS2_EXT_REFCOUNTED)) {
            ret = ocfs2_add_refcount_flag(inode, &di_et,
                              &ref_tree->rf_ci,
                              ref_root_bh, cpos,
                              p_cluster, num_clusters,
                              &dealloc, NULL);
            if (ret) {
                mlog_errno(ret);
                goto unlock;
            }

            data_changed = 1;
        }
        cpos += num_clusters;
    }

attach_xattr:
    if (oi->ip_dyn_features & OCFS2_HAS_XATTR_FL) {
        ret = ocfs2_xattr_attach_refcount_tree(inode, di_bh,
                               &ref_tree->rf_ci,
                               ref_root_bh,
                               &dealloc);
        if (ret) {
            mlog_errno(ret);
            goto unlock;
        }
    }

    if (data_changed) {
        ret = ocfs2_change_ctime(inode, di_bh);
        if (ret)
            mlog_errno(ret);
    }

unlock:
    ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
    brelse(ref_root_bh);

    if (!ret && ocfs2_dealloc_has_cluster(&dealloc)) {
        ocfs2_schedule_truncate_log_flush(osb, 1);
        ocfs2_run_deallocs(osb, &dealloc);
    }
out:
    /*
     * Empty the extent map so that we may get the right extent
     * record from the disk.
     */
    ocfs2_extent_map_trunc(inode, 0);

    return ret;
}

static int ocfs2_add_refcounted_extent(struct inode *inode,
                   struct ocfs2_extent_tree *et,
                   struct ocfs2_caching_info *ref_ci,
                   struct buffer_head *ref_root_bh,
                   u32 cpos, u32 p_cluster, u32 num_clusters,
                   unsigned int ext_flags,
                   struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret;
    handle_t *handle;
    int credits = 0;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_alloc_context *meta_ac = NULL;

    ret = ocfs2_lock_refcount_allocators(inode->i_sb,
                         p_cluster, num_clusters,
                         et, ref_ci,
                         ref_root_bh, &meta_ac,
                         NULL, &credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

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

    ret = ocfs2_insert_extent(handle, et, cpos,
            ocfs2_clusters_to_blocks(inode->i_sb, p_cluster),
            num_clusters, ext_flags, meta_ac);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    ret = ocfs2_increase_refcount(handle, ref_ci, ref_root_bh,
                      p_cluster, num_clusters,
                      meta_ac, dealloc);
    if (ret)
        mlog_errno(ret);

out_commit:
    ocfs2_commit_trans(osb, handle);
out:
    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);
    return ret;
}

static int ocfs2_duplicate_inline_data(struct inode *s_inode,
                       struct buffer_head *s_bh,
                       struct inode *t_inode,
                       struct buffer_head *t_bh)
{
    int ret;
    handle_t *handle;
    struct ocfs2_super *osb = OCFS2_SB(s_inode->i_sb);
    struct ocfs2_dinode *s_di = (struct ocfs2_dinode *)s_bh->b_data;
    struct ocfs2_dinode *t_di = (struct ocfs2_dinode *)t_bh->b_data;

    BUG_ON(!(OCFS2_I(s_inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL));

    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(t_inode), t_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    t_di->id2.i_data.id_count = s_di->id2.i_data.id_count;
    memcpy(t_di->id2.i_data.id_data, s_di->id2.i_data.id_data,
           le16_to_cpu(s_di->id2.i_data.id_count));
    spin_lock(&OCFS2_I(t_inode)->ip_lock);
    OCFS2_I(t_inode)->ip_dyn_features |= OCFS2_INLINE_DATA_FL;
    t_di->i_dyn_features = cpu_to_le16(OCFS2_I(t_inode)->ip_dyn_features);
    spin_unlock(&OCFS2_I(t_inode)->ip_lock);

    ocfs2_journal_dirty(handle, t_bh);

out_commit:
    ocfs2_commit_trans(osb, handle);
out:
    return ret;
}

static int ocfs2_duplicate_extent_list(struct inode *s_inode,
                struct inode *t_inode,
                struct buffer_head *t_bh,
                struct ocfs2_caching_info *ref_ci,
                struct buffer_head *ref_root_bh,
                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
    int ret = 0;
    u32 p_cluster, num_clusters, clusters, cpos;
    loff_t size;
    unsigned int ext_flags;
    struct ocfs2_extent_tree et;

    ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(t_inode), t_bh);

    size = i_size_read(s_inode);
    clusters = ocfs2_clusters_for_bytes(s_inode->i_sb, size);

    cpos = 0;
    while (cpos < clusters) {
        ret = ocfs2_get_clusters(s_inode, cpos, &p_cluster,
                     &num_clusters, &ext_flags);

        if (p_cluster) {
            ret = ocfs2_add_refcounted_extent(t_inode, &et,
                              ref_ci, ref_root_bh,
                              cpos, p_cluster,
                              num_clusters,
                              ext_flags,
                              dealloc);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }
        }

        cpos += num_clusters;
    }

out:
    return ret;
}

/*
 * change the new file's attributes to the src.
 *
 * reflink creates a snapshot of a file, that means the attributes
 * must be identical except for three exceptions - nlink, ino, and ctime.
 */
static int ocfs2_complete_reflink(struct inode *s_inode,
                  struct buffer_head *s_bh,
                  struct inode *t_inode,
                  struct buffer_head *t_bh,
                  bool preserve)
{
    int ret;
    handle_t *handle;
    struct ocfs2_dinode *s_di = (struct ocfs2_dinode *)s_bh->b_data;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)t_bh->b_data;
    loff_t size = i_size_read(s_inode);

    handle = ocfs2_start_trans(OCFS2_SB(t_inode->i_sb),
                   OCFS2_INODE_UPDATE_CREDITS);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        return ret;
    }

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

    spin_lock(&OCFS2_I(t_inode)->ip_lock);
    OCFS2_I(t_inode)->ip_clusters = OCFS2_I(s_inode)->ip_clusters;
    OCFS2_I(t_inode)->ip_attr = OCFS2_I(s_inode)->ip_attr;
    OCFS2_I(t_inode)->ip_dyn_features = OCFS2_I(s_inode)->ip_dyn_features;
    spin_unlock(&OCFS2_I(t_inode)->ip_lock);
    i_size_write(t_inode, size);
    t_inode->i_blocks = s_inode->i_blocks;

    di->i_xattr_inline_size = s_di->i_xattr_inline_size;
    di->i_clusters = s_di->i_clusters;
    di->i_size = s_di->i_size;
    di->i_dyn_features = s_di->i_dyn_features;
    di->i_attr = s_di->i_attr;

    if (preserve) {
        t_inode->i_uid = s_inode->i_uid;
        t_inode->i_gid = s_inode->i_gid;
        t_inode->i_mode = s_inode->i_mode;
        di->i_uid = s_di->i_uid;
        di->i_gid = s_di->i_gid;
        di->i_mode = s_di->i_mode;

        /*
         * update time.
         * we want mtime to appear identical to the source and
         * update ctime.
         */
        t_inode->i_ctime = CURRENT_TIME;

        di->i_ctime = cpu_to_le64(t_inode->i_ctime.tv_sec);
        di->i_ctime_nsec = cpu_to_le32(t_inode->i_ctime.tv_nsec);

        t_inode->i_mtime = s_inode->i_mtime;
        di->i_mtime = s_di->i_mtime;
        di->i_mtime_nsec = s_di->i_mtime_nsec;
    }

    ocfs2_journal_dirty(handle, t_bh);

out_commit:
    ocfs2_commit_trans(OCFS2_SB(t_inode->i_sb), handle);
    return ret;
}

static int ocfs2_create_reflink_node(struct inode *s_inode,
                     struct buffer_head *s_bh,
                     struct inode *t_inode,
                     struct buffer_head *t_bh,
                     bool preserve)
{
    int ret;
    struct buffer_head *ref_root_bh = NULL;
    struct ocfs2_cached_dealloc_ctxt dealloc;
    struct ocfs2_super *osb = OCFS2_SB(s_inode->i_sb);
    struct ocfs2_refcount_block *rb;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)s_bh->b_data;
    struct ocfs2_refcount_tree *ref_tree;

    ocfs2_init_dealloc_ctxt(&dealloc);

    ret = ocfs2_set_refcount_tree(t_inode, t_bh,
                      le64_to_cpu(di->i_refcount_loc));
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (OCFS2_I(s_inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
        ret = ocfs2_duplicate_inline_data(s_inode, s_bh,
                          t_inode, t_bh);
        if (ret)
            mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_lock_refcount_tree(osb, le64_to_cpu(di->i_refcount_loc),
                       1, &ref_tree, &ref_root_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }
    rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;

    ret = ocfs2_duplicate_extent_list(s_inode, t_inode, t_bh,
                      &ref_tree->rf_ci, ref_root_bh,
                      &dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out_unlock_refcount;
    }

out_unlock_refcount:
    ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
    brelse(ref_root_bh);
out:
    if (ocfs2_dealloc_has_cluster(&dealloc)) {
        ocfs2_schedule_truncate_log_flush(osb, 1);
        ocfs2_run_deallocs(osb, &dealloc);
    }

    return ret;
}

static int __ocfs2_reflink(struct dentry *old_dentry,
               struct buffer_head *old_bh,
               struct inode *new_inode,
               bool preserve)
{
    int ret;
    struct inode *inode = old_dentry->d_inode;
    struct buffer_head *new_bh = NULL;

    if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_SYSTEM_FILE) {
        ret = -EINVAL;
        mlog_errno(ret);
        goto out;
    }

    ret = filemap_fdatawrite(inode->i_mapping);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_attach_refcount_tree(inode, old_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    mutex_lock_nested(&new_inode->i_mutex, I_MUTEX_CHILD);
    ret = ocfs2_inode_lock_nested(new_inode, &new_bh, 1,
                      OI_LS_REFLINK_TARGET);
    if (ret) {
        mlog_errno(ret);
        goto out_unlock;
    }

    ret = ocfs2_create_reflink_node(inode, old_bh,
                    new_inode, new_bh, preserve);
    if (ret) {
        mlog_errno(ret);
        goto inode_unlock;
    }

    if (OCFS2_I(inode)->ip_dyn_features & OCFS2_HAS_XATTR_FL) {
        ret = ocfs2_reflink_xattrs(inode, old_bh,
                       new_inode, new_bh,
                       preserve);
        if (ret) {
            mlog_errno(ret);
            goto inode_unlock;
        }
    }

    ret = ocfs2_complete_reflink(inode, old_bh,
                     new_inode, new_bh, preserve);
    if (ret)
        mlog_errno(ret);

inode_unlock:
    ocfs2_inode_unlock(new_inode, 1);
    brelse(new_bh);
out_unlock:
    mutex_unlock(&new_inode->i_mutex);
out:
    if (!ret) {
        ret = filemap_fdatawait(inode->i_mapping);
        if (ret)
            mlog_errno(ret);
    }
    return ret;
}

static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
             struct dentry *new_dentry, bool preserve)
{
    int error;
    struct inode *inode = old_dentry->d_inode;
    struct buffer_head *old_bh = NULL;
    struct inode *new_orphan_inode = NULL;

    if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
        return -EOPNOTSUPP;

    error = ocfs2_create_inode_in_orphan(dir, inode->i_mode,
                         &new_orphan_inode);
    if (error) {
        mlog_errno(error);
        goto out;
    }

    error = ocfs2_inode_lock(inode, &old_bh, 1);
    if (error) {
        mlog_errno(error);
        goto out;
    }

    down_write(&OCFS2_I(inode)->ip_xattr_sem);
    down_write(&OCFS2_I(inode)->ip_alloc_sem);
    error = __ocfs2_reflink(old_dentry, old_bh,
                new_orphan_inode, preserve);
    up_write(&OCFS2_I(inode)->ip_alloc_sem);
    up_write(&OCFS2_I(inode)->ip_xattr_sem);

    ocfs2_inode_unlock(inode, 1);
    brelse(old_bh);

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

    /* If the security isn't preserved, we need to re-initialize them. */
    if (!preserve) {
        error = ocfs2_init_security_and_acl(dir, new_orphan_inode,
                            &new_dentry->d_name);
        if (error)
            mlog_errno(error);
    }
out:
    if (!error) {
        error = ocfs2_mv_orphaned_inode_to_new(dir, new_orphan_inode,
                               new_dentry);
        if (error)
            mlog_errno(error);
    }

    if (new_orphan_inode) {
        /*
         * We need to open_unlock the inode no matter whether we
         * succeed or not, so that other nodes can delete it later.
         */
        ocfs2_open_unlock(new_orphan_inode);
        if (error)
            iput(new_orphan_inode);
    }

    return error;
}

/*
 * Below here are the bits used by OCFS2_IOC_REFLINK() to fake
 * sys_reflink().  This will go away when vfs_reflink() exists in
 * fs/namei.c.
 */

/* copied from may_create in VFS. */
static inline int ocfs2_may_create(struct inode *dir, struct dentry *child)
{
    if (child->d_inode)
        return -EEXIST;
    if (IS_DEADDIR(dir))
        return -ENOENT;
    return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}

static int ocfs2_vfs_reflink(struct dentry *old_dentry, struct inode *dir,
                 struct dentry *new_dentry, bool preserve)
{
    struct inode *inode = old_dentry->d_inode;
    int error;

    if (!inode)
        return -ENOENT;

    error = ocfs2_may_create(dir, new_dentry);
    if (error)
        return error;

    if (dir->i_sb != inode->i_sb)
        return -EXDEV;

    /*
     * A reflink to an append-only or immutable file cannot be created.
     */
    if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
        return -EPERM;

    /* Only regular files can be reflinked. */
    if (!S_ISREG(inode->i_mode))
        return -EPERM;

    /*
     * If the caller wants to preserve ownership, they require the
     * rights to do so.
     */
    if (preserve) {
        if ((current_fsuid() != inode->i_uid) && !capable(CAP_CHOWN))
            return -EPERM;
        if (!in_group_p(inode->i_gid) && !capable(CAP_CHOWN))
            return -EPERM;
    }

    /*
     * If the caller is modifying any aspect of the attributes, they
     * are not creating a snapshot.  They need read permission on the
     * file.
     */
    if (!preserve) {
        error = inode_permission(inode, MAY_READ);
        if (error)
            return error;
    }

    mutex_lock(&inode->i_mutex);
    dquot_initialize(dir);
    error = ocfs2_reflink(old_dentry, dir, new_dentry, preserve);
    mutex_unlock(&inode->i_mutex);
    if (!error)
        fsnotify_create(dir, new_dentry);
    return error;
}
/*
 * Most codes are copied from sys_linkat.
 */
int ocfs2_reflink_ioctl(struct inode *inode,
            const char __user *oldname,
            const char __user *newname,
            bool preserve)
{
    struct dentry *new_dentry;
    struct path old_path, new_path;
    int error;

    if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
        return -EOPNOTSUPP;

    error = user_path_at(AT_FDCWD, oldname, 0, &old_path);
    if (error) {
        mlog_errno(error);
        return error;
    }

    new_dentry = user_path_create(AT_FDCWD, newname, &new_path, 0);
    error = PTR_ERR(new_dentry);
    if (IS_ERR(new_dentry)) {
        mlog_errno(error);
        goto out;
    }

    error = -EXDEV;
    if (old_path.mnt != new_path.mnt) {
        mlog_errno(error);
        goto out_dput;
    }

    error = ocfs2_vfs_reflink(old_path.dentry,
                  new_path.dentry->d_inode,
                  new_dentry, preserve);
out_dput:
    done_path_create(&new_path, new_dentry);
out:
    path_put(&old_path);

    return error;
}