// SPDX-License-Identifier: GPL-2.0-only
/*
 * move_extents.c
 *
 * Copyright (C) 2011 Oracle.  All rights reserved.
 */
#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 "localalloc.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, inode, 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) {
                ret = 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);
                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);
        }

        ocfs2_update_inode_fsync_trans(handle, inode, 0);
out:
        ocfs2_free_path(path);
        return ret;
}

/*
 * lock allocator, and reserve appropriate number of bits for
 * meta blocks.
 */
static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
                                        struct ocfs2_extent_tree *et,
                                        u32 clusters_to_move,
                                        u32 extents_to_split,
                                        struct ocfs2_alloc_context **meta_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(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;
        }


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

        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);
        int need_free = 0;

        if ((ext_flags & OCFS2_EXT_REFCOUNTED) && *len) {
                BUG_ON(!ocfs2_is_refcount_inode(inode));
                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_meta_allocator_move_extents(inode, &context->et,
                                                *len, 1,
                                                &context->meta_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;
         */

        inode_lock(tl_inode);

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

        /*
         * Make sure ocfs2_reserve_cluster is called after
         * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
         *
         * If ocfs2_reserve_cluster is called
         * before __ocfs2_flush_truncate_log, dead lock on global bitmap
         * may happen.
         *
         */
        ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac);
        if (ret) {
                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;
                        need_free = 1;
                        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:
        if (need_free && context->data_ac) {
                struct ocfs2_alloc_context *data_ac = context->data_ac;

                if (context->data_ac->ac_which == OCFS2_AC_USE_LOCAL)
                        ocfs2_free_local_alloc_bits(osb, handle, data_ac,
                                        new_phys_cpos, new_len);
                else
                        ocfs2_free_clusters(handle,
                                        data_ac->ac_inode,
                                        data_ac->ac_bh,
                                        ocfs2_clusters_to_blocks(osb->sb, new_phys_cpos),
                                        new_len);
        }

        ocfs2_commit_trans(osb, handle);

out_unlock_mutex:
        inode_unlock(tl_inode);

        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 >= ((u64)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;
        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);
        /*
         * 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;

        /*
         * 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;

        /*
         * 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_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_is_refcount_inode(inode));
                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_meta_allocator_move_extents(inode, &context->et,
                                                len, 1,
                                                &context->meta_ac,
                                                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;
        }

        inode_lock(gb_inode);

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

        inode_lock(tl_inode);

        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) {
                ocfs2_rollback_alloc_dinode_counts(gb_inode, gb_bh, len,
                                               le16_to_cpu(gd->bg_chain));
                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:
        inode_unlock(tl_inode);

        ocfs2_inode_unlock(gb_inode, 1);
out_unlock_gb_mutex:
        inode_unlock(gb_inode);
        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 ((i_size_read(inode) == 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 (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
                return -EROFS;

        inode_lock(inode);

        /*
         * 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(inode);
        di->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
        di->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
        ocfs2_update_inode_fsync_trans(handle, inode, 0);

        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:
        inode_unlock(inode);

        return status;
}

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

        struct inode *inode = file_inode(filp);
        struct ocfs2_move_extents range;
        struct ocfs2_move_extents_context *context;

        if (!argp)
                return -EINVAL;

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

        if ((!S_ISREG(inode->i_mode)) || !(filp->f_mode & FMODE_WRITE)) {
                status = -EPERM;
                goto out_drop;

        }

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

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

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

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

        if (range.me_start > i_size_read(inode)) {
                status = -EINVAL;
                goto out_free;
        }

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

        context->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_copy;
        }

        status = ocfs2_move_extents(context);
        if (status)
                mlog_errno(status);
out_copy:
        /*
         * 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 (copy_to_user(argp, &range, sizeof(range)))
                status = -EFAULT;

out_free:
        kfree(context);
out_drop:
        mnt_drop_write_file(filp);

        return status;
}