move_extents.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * move_extents.c
 *
 * Copyright (C) 2011 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/fs.h>
#include <linux/types.h>
#include <linux/mount.h>
#include <linux/swap.h>

#include <cluster/masklog.h>

#include "ocfs2.h"
#include "ocfs2_ioctl.h"

#include "alloc.h"
#include "aops.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "journal.h"
#include "suballoc.h"
#include "uptodate.h"
#include "super.h"
#include "dir.h"
#include "buffer_head_io.h"
#include "sysfile.h"
#include "refcounttree.h"
#include "move_extents.h"

struct ocfs2_move_extents_context {
    struct inode *inode;
    struct file *file;
    int auto_defrag;
    int partial;
    int credits;
    u32 new_phys_cpos;
    u32 clusters_moved;
    u64 refcount_loc;
    struct ocfs2_move_extents *range;
    struct ocfs2_extent_tree et;
    struct ocfs2_alloc_context *meta_ac;
    struct ocfs2_alloc_context *data_ac;
    struct ocfs2_cached_dealloc_ctxt dealloc;
};

static int __ocfs2_move_extent(handle_t *handle,
                   struct ocfs2_move_extents_context *context,
                   u32 cpos, u32 len, u32 p_cpos, u32 new_p_cpos,
                   int ext_flags)
{
    int ret = 0, index;
    struct inode *inode = context->inode;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_extent_rec *rec, replace_rec;
    struct ocfs2_path *path = NULL;
    struct ocfs2_extent_list *el;
    u64 ino = ocfs2_metadata_cache_owner(context->et.et_ci);
    u64 old_blkno = ocfs2_clusters_to_blocks(inode->i_sb, p_cpos);

    ret = ocfs2_duplicate_clusters_by_page(handle, context->file, cpos,
                           p_cpos, new_p_cpos, len);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    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(inode->i_sb,
                                   new_p_cpos));

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

    ret = ocfs2_find_path(INODE_CACHE(inode), 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(inode->i_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;
    }

    rec = &el->l_recs[index];

    BUG_ON(ext_flags != rec->e_flags);
    /*
     * after moving/defraging to new location, the extent is not going
     * to be refcounted anymore.
     */
    replace_rec.e_flags = ext_flags & ~OCFS2_EXT_REFCOUNTED;

    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode),
                      context->et.et_root_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_split_extent(handle, &context->et, path, index,
                 &replace_rec, context->meta_ac,
                 &context->dealloc);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ocfs2_journal_dirty(handle, context->et.et_root_bh);

    context->new_phys_cpos = new_p_cpos;

    /*
     * need I to append truncate log for old clusters?
     */
    if (old_blkno) {
        if (ext_flags & OCFS2_EXT_REFCOUNTED)
            ret = ocfs2_decrease_refcount(inode, handle,
                    ocfs2_blocks_to_clusters(osb->sb,
                                 old_blkno),
                    len, context->meta_ac,
                    &context->dealloc, 1);
        else
            ret = ocfs2_truncate_log_append(osb, handle,
                            old_blkno, len);
    }

out:
    return ret;
}

/*
 * lock allocators, and reserving appropriate number of bits for
 * meta blocks and data clusters.
 *
 * in some cases, we don't need to reserve clusters, just let data_ac
 * be NULL.
 */
static int ocfs2_lock_allocators_move_extents(struct inode *inode,
                    struct ocfs2_extent_tree *et,
                    u32 clusters_to_move,
                    u32 extents_to_split,
                    struct ocfs2_alloc_context **meta_ac,
                    struct ocfs2_alloc_context **data_ac,
                    int extra_blocks,
                    int *credits)
{
    int ret, num_free_extents;
    unsigned int max_recs_needed = 2 * extents_to_split + clusters_to_move;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

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

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

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

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

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

    mlog(0, "reserve metadata_blocks: %d, data_clusters: %u, credits: %d\n",
         extra_blocks, clusters_to_move, *credits);
out:
    if (ret) {
        if (*meta_ac) {
            ocfs2_free_alloc_context(*meta_ac);
            *meta_ac = NULL;
        }
    }

    return ret;
}

/*
 * Using one journal handle to guarantee the data consistency in case
 * crash happens anywhere.
 *
 *  XXX: defrag can end up with finishing partial extent as requested,
 * due to not enough contiguous clusters can be found in allocator.
 */
static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
                   u32 cpos, u32 phys_cpos, u32 *len, int ext_flags)
{
    int ret, credits = 0, extra_blocks = 0, partial = context->partial;
    handle_t *handle;
    struct inode *inode = context->inode;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct inode *tl_inode = osb->osb_tl_inode;
    struct ocfs2_refcount_tree *ref_tree = NULL;
    u32 new_phys_cpos, new_len;
    u64 phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, phys_cpos);

    if ((ext_flags & OCFS2_EXT_REFCOUNTED) && *len) {

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

        BUG_ON(!context->refcount_loc);

        ret = ocfs2_lock_refcount_tree(osb, context->refcount_loc, 1,
                           &ref_tree, NULL);
        if (ret) {
            mlog_errno(ret);
            return ret;
        }

        ret = ocfs2_prepare_refcount_change_for_del(inode,
                            context->refcount_loc,
                            phys_blkno,
                            *len,
                            &credits,
                            &extra_blocks);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
                         &context->meta_ac,
                         &context->data_ac,
                         extra_blocks, &credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * should be using allocation reservation strategy there?
     *
     * if (context->data_ac)
     *  context->data_ac->ac_resv = &OCFS2_I(inode)->ip_la_data_resv;
     */

    mutex_lock(&tl_inode->i_mutex);

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

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

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

    /*
     * allowing partial extent moving is kind of 'pros and cons', it makes
     * whole defragmentation less likely to fail, on the contrary, the bad
     * thing is it may make the fs even more fragmented after moving, let
     * userspace make a good decision here.
     */
    if (new_len != *len) {
        mlog(0, "len_claimed: %u, len: %u\n", new_len, *len);
        if (!partial) {
            context->range->me_flags &= ~OCFS2_MOVE_EXT_FL_COMPLETE;
            ret = -ENOSPC;
            goto out_commit;
        }
    }

    mlog(0, "cpos: %u, phys_cpos: %u, new_phys_cpos: %u\n", cpos,
         phys_cpos, new_phys_cpos);

    ret = __ocfs2_move_extent(handle, context, cpos, new_len, phys_cpos,
                  new_phys_cpos, ext_flags);
    if (ret)
        mlog_errno(ret);

    if (partial && (new_len != *len))
        *len = new_len;

    /*
     * Here we should write the new page out first if we are
     * in write-back mode.
     */
    ret = ocfs2_cow_sync_writeback(inode->i_sb, context->inode, cpos, *len);
    if (ret)
        mlog_errno(ret);

out_commit:
    ocfs2_commit_trans(osb, handle);

out_unlock_mutex:
    mutex_unlock(&tl_inode->i_mutex);

    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;
    }

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

    return ret;
}

/*
 * find the victim alloc group, where #blkno fits.
 */
static int ocfs2_find_victim_alloc_group(struct inode *inode,
                     u64 vict_blkno,
                     int type, int slot,
                     int *vict_bit,
                     struct buffer_head **ret_bh)
{
    int ret, i, bits_per_unit = 0;
    u64 blkno;
    char namebuf[40];

    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct buffer_head *ac_bh = NULL, *gd_bh = NULL;
    struct ocfs2_chain_list *cl;
    struct ocfs2_chain_rec *rec;
    struct ocfs2_dinode *ac_dinode;
    struct ocfs2_group_desc *bg;

    ocfs2_sprintf_system_inode_name(namebuf, sizeof(namebuf), type, slot);
    ret = ocfs2_lookup_ino_from_name(osb->sys_root_inode, namebuf,
                     strlen(namebuf), &blkno);
    if (ret) {
        ret = -ENOENT;
        goto out;
    }

    ret = ocfs2_read_blocks_sync(osb, blkno, 1, &ac_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ac_dinode = (struct ocfs2_dinode *)ac_bh->b_data;
    cl = &(ac_dinode->id2.i_chain);
    rec = &(cl->cl_recs[0]);

    if (type == GLOBAL_BITMAP_SYSTEM_INODE)
        bits_per_unit = osb->s_clustersize_bits -
                    inode->i_sb->s_blocksize_bits;
    /*
     * 'vict_blkno' was out of the valid range.
     */
    if ((vict_blkno < le64_to_cpu(rec->c_blkno)) ||
        (vict_blkno >= (le32_to_cpu(ac_dinode->id1.bitmap1.i_total) <<
                bits_per_unit))) {
        ret = -EINVAL;
        goto out;
    }

    for (i = 0; i < le16_to_cpu(cl->cl_next_free_rec); i++) {

        rec = &(cl->cl_recs[i]);
        if (!rec)
            continue;

        bg = NULL;

        do {
            if (!bg)
                blkno = le64_to_cpu(rec->c_blkno);
            else
                blkno = le64_to_cpu(bg->bg_next_group);

            if (gd_bh) {
                brelse(gd_bh);
                gd_bh = NULL;
            }

            ret = ocfs2_read_blocks_sync(osb, blkno, 1, &gd_bh);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            bg = (struct ocfs2_group_desc *)gd_bh->b_data;

            if (vict_blkno < (le64_to_cpu(bg->bg_blkno) +
                        le16_to_cpu(bg->bg_bits))) {

                *ret_bh = gd_bh;
                *vict_bit = (vict_blkno - blkno) >>
                            bits_per_unit;
                mlog(0, "find the victim group: #%llu, "
                     "total_bits: %u, vict_bit: %u\n",
                     blkno, le16_to_cpu(bg->bg_bits),
                     *vict_bit);
                goto out;
            }

        } while (le64_to_cpu(bg->bg_next_group));
    }

    ret = -EINVAL;
out:
    brelse(ac_bh);

    /*
     * caller has to release the gd_bh properly.
     */
    return ret;
}

/*
 * XXX: helper to validate and adjust moving goal.
 */
static int ocfs2_validate_and_adjust_move_goal(struct inode *inode,
                           struct ocfs2_move_extents *range)
{
    int ret, goal_bit = 0;

    struct buffer_head *gd_bh = NULL;
    struct ocfs2_group_desc *bg = NULL;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    int c_to_b = 1 << (osb->s_clustersize_bits -
                    inode->i_sb->s_blocksize_bits);

    /*
     * make goal become cluster aligned.
     */
    range->me_goal = ocfs2_block_to_cluster_start(inode->i_sb,
                              range->me_goal);
    /*
     * moving goal is not allowd to start with a group desc blok(#0 blk)
     * let's compromise to the latter cluster.
     */
    if (range->me_goal == le64_to_cpu(bg->bg_blkno))
        range->me_goal += c_to_b;

    /*
     * validate goal sits within global_bitmap, and return the victim
     * group desc
     */
    ret = ocfs2_find_victim_alloc_group(inode, range->me_goal,
                        GLOBAL_BITMAP_SYSTEM_INODE,
                        OCFS2_INVALID_SLOT,
                        &goal_bit, &gd_bh);
    if (ret)
        goto out;

    bg = (struct ocfs2_group_desc *)gd_bh->b_data;

    /*
     * movement is not gonna cross two groups.
     */
    if ((le16_to_cpu(bg->bg_bits) - goal_bit) * osb->s_clustersize <
                                range->me_len) {
        ret = -EINVAL;
        goto out;
    }
    /*
     * more exact validations/adjustments will be performed later during
     * moving operation for each extent range.
     */
    mlog(0, "extents get ready to be moved to #%llu block\n",
         range->me_goal);

out:
    brelse(gd_bh);

    return ret;
}

static void ocfs2_probe_alloc_group(struct inode *inode, struct buffer_head *bh,
                    int *goal_bit, u32 move_len, u32 max_hop,
                    u32 *phys_cpos)
{
    int i, used, last_free_bits = 0, base_bit = *goal_bit;
    struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;
    u32 base_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
                         le64_to_cpu(gd->bg_blkno));

    for (i = base_bit; i < le16_to_cpu(gd->bg_bits); i++) {

        used = ocfs2_test_bit(i, (unsigned long *)gd->bg_bitmap);
        if (used) {
            /*
             * we even tried searching the free chunk by jumping
             * a 'max_hop' distance, but still failed.
             */
            if ((i - base_bit) > max_hop) {
                *phys_cpos = 0;
                break;
            }

            if (last_free_bits)
                last_free_bits = 0;

            continue;
        } else
            last_free_bits++;

        if (last_free_bits == move_len) {
            *goal_bit = i;
            *phys_cpos = base_cpos + i;
            break;
        }
    }

    mlog(0, "found phys_cpos: %u to fit the wanted moving.\n", *phys_cpos);
}

static int ocfs2_alloc_dinode_update_counts(struct inode *inode,
                       handle_t *handle,
                       struct buffer_head *di_bh,
                       u32 num_bits,
                       u16 chain)
{
    int ret;
    u32 tmp_used;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *) di_bh->b_data;
    struct ocfs2_chain_list *cl =
                (struct ocfs2_chain_list *) &di->id2.i_chain;

    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    }

    tmp_used = le32_to_cpu(di->id1.bitmap1.i_used);
    di->id1.bitmap1.i_used = cpu_to_le32(num_bits + tmp_used);
    le32_add_cpu(&cl->cl_recs[chain].c_free, -num_bits);
    ocfs2_journal_dirty(handle, di_bh);

out:
    return ret;
}

static inline int ocfs2_block_group_set_bits(handle_t *handle,
                         struct inode *alloc_inode,
                         struct ocfs2_group_desc *bg,
                         struct buffer_head *group_bh,
                         unsigned int bit_off,
                         unsigned int num_bits)
{
    int status;
    void *bitmap = bg->bg_bitmap;
    int journal_type = OCFS2_JOURNAL_ACCESS_WRITE;

    /* All callers get the descriptor via
     * ocfs2_read_group_descriptor().  Any corruption is a code bug. */
    BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(bg));
    BUG_ON(le16_to_cpu(bg->bg_free_bits_count) < num_bits);

    mlog(0, "block_group_set_bits: off = %u, num = %u\n", bit_off,
         num_bits);

    if (ocfs2_is_cluster_bitmap(alloc_inode))
        journal_type = OCFS2_JOURNAL_ACCESS_UNDO;

    status = ocfs2_journal_access_gd(handle,
                     INODE_CACHE(alloc_inode),
                     group_bh,
                     journal_type);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    le16_add_cpu(&bg->bg_free_bits_count, -num_bits);
    if (le16_to_cpu(bg->bg_free_bits_count) > le16_to_cpu(bg->bg_bits)) {
        ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit"
                " count %u but claims %u are freed. num_bits %d",
                (unsigned long long)le64_to_cpu(bg->bg_blkno),
                le16_to_cpu(bg->bg_bits),
                le16_to_cpu(bg->bg_free_bits_count), num_bits);
        return -EROFS;
    }
    while (num_bits--)
        ocfs2_set_bit(bit_off++, bitmap);

    ocfs2_journal_dirty(handle, group_bh);

bail:
    return status;
}

static int ocfs2_move_extent(struct ocfs2_move_extents_context *context,
                 u32 cpos, u32 phys_cpos, u32 *new_phys_cpos,
                 u32 len, int ext_flags)
{
    int ret, credits = 0, extra_blocks = 0, goal_bit = 0;
    handle_t *handle;
    struct inode *inode = context->inode;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct inode *tl_inode = osb->osb_tl_inode;
    struct inode *gb_inode = NULL;
    struct buffer_head *gb_bh = NULL;
    struct buffer_head *gd_bh = NULL;
    struct ocfs2_group_desc *gd;
    struct ocfs2_refcount_tree *ref_tree = NULL;
    u32 move_max_hop = ocfs2_blocks_to_clusters(inode->i_sb,
                            context->range->me_threshold);
    u64 phys_blkno, new_phys_blkno;

    phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, phys_cpos);

    if ((ext_flags & OCFS2_EXT_REFCOUNTED) && len) {

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

        BUG_ON(!context->refcount_loc);

        ret = ocfs2_lock_refcount_tree(osb, context->refcount_loc, 1,
                           &ref_tree, NULL);
        if (ret) {
            mlog_errno(ret);
            return ret;
        }

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

    ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
                         &context->meta_ac,
                         NULL, extra_blocks, &credits);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * need to count 2 extra credits for global_bitmap inode and
     * group descriptor.
     */
    credits += OCFS2_INODE_UPDATE_CREDITS + 1;

    /*
     * ocfs2_move_extent() didn't reserve any clusters in lock_allocators()
     * logic, while we still need to lock the global_bitmap.
     */
    gb_inode = ocfs2_get_system_file_inode(osb, GLOBAL_BITMAP_SYSTEM_INODE,
                           OCFS2_INVALID_SLOT);
    if (!gb_inode) {
        mlog(ML_ERROR, "unable to get global_bitmap inode\n");
        ret = -EIO;
        goto out;
    }

    mutex_lock(&gb_inode->i_mutex);

    ret = ocfs2_inode_lock(gb_inode, &gb_bh, 1);
    if (ret) {
        mlog_errno(ret);
        goto out_unlock_gb_mutex;
    }

    mutex_lock(&tl_inode->i_mutex);

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

    new_phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, *new_phys_cpos);
    ret = ocfs2_find_victim_alloc_group(inode, new_phys_blkno,
                        GLOBAL_BITMAP_SYSTEM_INODE,
                        OCFS2_INVALID_SLOT,
                        &goal_bit, &gd_bh);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    /*
     * probe the victim cluster group to find a proper
     * region to fit wanted movement, it even will perfrom
     * a best-effort attempt by compromising to a threshold
     * around the goal.
     */
    ocfs2_probe_alloc_group(inode, gd_bh, &goal_bit, len, move_max_hop,
                new_phys_cpos);
    if (!*new_phys_cpos) {
        ret = -ENOSPC;
        goto out_commit;
    }

    ret = __ocfs2_move_extent(handle, context, cpos, len, phys_cpos,
                  *new_phys_cpos, ext_flags);
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    gd = (struct ocfs2_group_desc *)gd_bh->b_data;
    ret = ocfs2_alloc_dinode_update_counts(gb_inode, handle, gb_bh, len,
                           le16_to_cpu(gd->bg_chain));
    if (ret) {
        mlog_errno(ret);
        goto out_commit;
    }

    ret = ocfs2_block_group_set_bits(handle, gb_inode, gd, gd_bh,
                     goal_bit, len);
    if (ret)
        mlog_errno(ret);

    /*
     * Here we should write the new page out first if we are
     * in write-back mode.
     */
    ret = ocfs2_cow_sync_writeback(inode->i_sb, context->inode, cpos, len);
    if (ret)
        mlog_errno(ret);

out_commit:
    ocfs2_commit_trans(osb, handle);
    brelse(gd_bh);

out_unlock_tl_inode:
    mutex_unlock(&tl_inode->i_mutex);

    ocfs2_inode_unlock(gb_inode, 1);
out_unlock_gb_mutex:
    mutex_unlock(&gb_inode->i_mutex);
    brelse(gb_bh);
    iput(gb_inode);

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

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

    return ret;
}

/*
 * Helper to calculate the defraging length in one run according to threshold.
 */
static void ocfs2_calc_extent_defrag_len(u32 *alloc_size, u32 *len_defraged,
                     u32 threshold, int *skip)
{
    if ((*alloc_size + *len_defraged) < threshold) {
        /*
         * proceed defragmentation until we meet the thresh
         */
        *len_defraged += *alloc_size;
    } else if (*len_defraged == 0) {
        /*
         * XXX: skip a large extent.
         */
        *skip = 1;
    } else {
        /*
         * split this extent to coalesce with former pieces as
         * to reach the threshold.
         *
         * we're done here with one cycle of defragmentation
         * in a size of 'thresh', resetting 'len_defraged'
         * forces a new defragmentation.
         */
        *alloc_size = threshold - *len_defraged;
        *len_defraged = 0;
    }
}

static int __ocfs2_move_extents_range(struct buffer_head *di_bh,
                struct ocfs2_move_extents_context *context)
{
    int ret = 0, flags, do_defrag, skip = 0;
    u32 cpos, phys_cpos, move_start, len_to_move, alloc_size;
    u32 len_defraged = 0, defrag_thresh = 0, new_phys_cpos = 0;

    struct inode *inode = context->inode;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
    struct ocfs2_move_extents *range = context->range;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if ((inode->i_size == 0) || (range->me_len == 0))
        return 0;

    if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL)
        return 0;

    context->refcount_loc = le64_to_cpu(di->i_refcount_loc);

    ocfs2_init_dinode_extent_tree(&context->et, INODE_CACHE(inode), di_bh);
    ocfs2_init_dealloc_ctxt(&context->dealloc);

    /*
     * TO-DO XXX:
     *
     * - xattr extents.
     */

    do_defrag = context->auto_defrag;

    /*
     * extents moving happens in unit of clusters, for the sake
     * of simplicity, we may ignore two clusters where 'byte_start'
     * and 'byte_start + len' were within.
     */
    move_start = ocfs2_clusters_for_bytes(osb->sb, range->me_start);
    len_to_move = (range->me_start + range->me_len) >>
                        osb->s_clustersize_bits;
    if (len_to_move >= move_start)
        len_to_move -= move_start;
    else
        len_to_move = 0;

    if (do_defrag) {
        defrag_thresh = range->me_threshold >> osb->s_clustersize_bits;
        if (defrag_thresh <= 1)
            goto done;
    } else
        new_phys_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
                             range->me_goal);

    mlog(0, "Inode: %llu, start: %llu, len: %llu, cstart: %u, clen: %u, "
         "thresh: %u\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         (unsigned long long)range->me_start,
         (unsigned long long)range->me_len,
         move_start, len_to_move, defrag_thresh);

    cpos = move_start;
    while (len_to_move) {
        ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &alloc_size,
                     &flags);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (alloc_size > len_to_move)
            alloc_size = len_to_move;

        /*
         * XXX: how to deal with a hole:
         *
         * - skip the hole of course
         * - force a new defragmentation
         */
        if (!phys_cpos) {
            if (do_defrag)
                len_defraged = 0;

            goto next;
        }

        if (do_defrag) {
            ocfs2_calc_extent_defrag_len(&alloc_size, &len_defraged,
                             defrag_thresh, &skip);
            /*
             * skip large extents
             */
            if (skip) {
                skip = 0;
                goto next;
            }

            mlog(0, "#Defrag: cpos: %u, phys_cpos: %u, "
                 "alloc_size: %u, len_defraged: %u\n",
                 cpos, phys_cpos, alloc_size, len_defraged);

            ret = ocfs2_defrag_extent(context, cpos, phys_cpos,
                          &alloc_size, flags);
        } else {
            ret = ocfs2_move_extent(context, cpos, phys_cpos,
                        &new_phys_cpos, alloc_size,
                        flags);

            new_phys_cpos += alloc_size;
        }

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

        context->clusters_moved += alloc_size;
next:
        cpos += alloc_size;
        len_to_move -= alloc_size;
    }

done:
    range->me_flags |= OCFS2_MOVE_EXT_FL_COMPLETE;

out:
    range->me_moved_len = ocfs2_clusters_to_bytes(osb->sb,
                              context->clusters_moved);
    range->me_new_offset = ocfs2_clusters_to_bytes(osb->sb,
                               context->new_phys_cpos);

    ocfs2_schedule_truncate_log_flush(osb, 1);
    ocfs2_run_deallocs(osb, &context->dealloc);

    return ret;
}

static int ocfs2_move_extents(struct ocfs2_move_extents_context *context)
{
    int status;
    handle_t *handle;
    struct inode *inode = context->inode;
    struct ocfs2_dinode *di;
    struct buffer_head *di_bh = NULL;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if (!inode)
        return -ENOENT;

    if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
        return -EROFS;

    mutex_lock(&inode->i_mutex);

    /*
     * This prevents concurrent writes from other nodes
     */
    status = ocfs2_rw_lock(inode, 1);
    if (status) {
        mlog_errno(status);
        goto out;
    }

    status = ocfs2_inode_lock(inode, &di_bh, 1);
    if (status) {
        mlog_errno(status);
        goto out_rw_unlock;
    }

    /*
     * rememer ip_xattr_sem also needs to be held if necessary
     */
    down_write(&OCFS2_I(inode)->ip_alloc_sem);

    status = __ocfs2_move_extents_range(di_bh, context);

    up_write(&OCFS2_I(inode)->ip_alloc_sem);
    if (status) {
        mlog_errno(status);
        goto out_inode_unlock;
    }

    /*
     * We update ctime for these changes
     */
    handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
    if (IS_ERR(handle)) {
        status = PTR_ERR(handle);
        mlog_errno(status);
        goto out_inode_unlock;
    }

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

    di = (struct ocfs2_dinode *)di_bh->b_data;
    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(osb, handle);

out_inode_unlock:
    brelse(di_bh);
    ocfs2_inode_unlock(inode, 1);
out_rw_unlock:
    ocfs2_rw_unlock(inode, 1);
out:
    mutex_unlock(&inode->i_mutex);

    return status;
}

int ocfs2_ioctl_move_extents(struct file *filp, void __user *argp)
{
    int status;

    struct inode *inode = filp->f_path.dentry->d_inode;
    struct ocfs2_move_extents range;
    struct ocfs2_move_extents_context *context = NULL;

    status = mnt_want_write_file(filp);
    if (status)
        return status;

    if ((!S_ISREG(inode->i_mode)) || !(filp->f_mode & FMODE_WRITE))
        goto out;

    if (inode->i_flags & (S_IMMUTABLE|S_APPEND)) {
        status = -EPERM;
        goto out;
    }

    context = kzalloc(sizeof(struct ocfs2_move_extents_context), GFP_NOFS);
    if (!context) {
        status = -ENOMEM;
        mlog_errno(status);
        goto out;
    }

    context->inode = inode;
    context->file = filp;

    if (argp) {
        if (copy_from_user(&range, argp, sizeof(range))) {
            status = -EFAULT;
            goto out;
        }
    } else {
        status = -EINVAL;
        goto out;
    }

    if (range.me_start > i_size_read(inode))
        goto out;

    if (range.me_start + range.me_len > i_size_read(inode))
            range.me_len = i_size_read(inode) - range.me_start;

    context->range = &range;

    if (range.me_flags & OCFS2_MOVE_EXT_FL_AUTO_DEFRAG) {
        context->auto_defrag = 1;
        /*
         * ok, the default theshold for the defragmentation
         * is 1M, since our maximum clustersize was 1M also.
         * any thought?
         */
        if (!range.me_threshold)
            range.me_threshold = 1024 * 1024;

        if (range.me_threshold > i_size_read(inode))
            range.me_threshold = i_size_read(inode);

        if (range.me_flags & OCFS2_MOVE_EXT_FL_PART_DEFRAG)
            context->partial = 1;
    } else {
        /*
         * first best-effort attempt to validate and adjust the goal
         * (physical address in block), while it can't guarantee later
         * operation can succeed all the time since global_bitmap may
         * change a bit over time.
         */

        status = ocfs2_validate_and_adjust_move_goal(inode, &range);
        if (status)
            goto out;
    }

    status = ocfs2_move_extents(context);
    if (status)
        mlog_errno(status);
out:
    /*
     * movement/defragmentation may end up being partially completed,
     * that's the reason why we need to return userspace the finished
     * length and new_offset even if failure happens somewhere.
     */
    if (argp) {
        if (copy_to_user(argp, &range, sizeof(range)))
            status = -EFAULT;
    }

    kfree(context);

    mnt_drop_write_file(filp);

    return status;
}