Inode preallocation consists of two parts (used and unused) fully controlled
by inode, so it must be discarded before swap extents.
Currently we may skip drop_preallocation if file is sparse.

This patch does:
- Moves ext4_discard_preallocations to ext4_swap_extents.
  This makes more readable and reliable for future changes.
- Cleanup main move_extent loop

xfstests:ext4/024 (pended: 
https://github.com/dmonakhov/xfstests/commit/7a4763963f73ea5d5bba45eefa484494aa3df7cf)
Signed-off-by: Dmitry Monakhov <dmonak...@openvz.org>
---
 fs/ext4/extents.c     |  2 ++
 fs/ext4/move_extent.c | 17 +++++------------
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index d7ccb7f..757ffb8 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5799,9 +5799,11 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
        BUG_ON(!inode_is_locked(inode1));
        BUG_ON(!inode_is_locked(inode2));
 
+       ext4_discard_preallocations(inode1);
        *erp = ext4_es_remove_extent(inode1, lblk1, count);
        if (unlikely(*erp))
                return 0;
+       ext4_discard_preallocations(inode2);
        *erp = ext4_es_remove_extent(inode2, lblk2, count);
        if (unlikely(*erp))
                return 0;
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 6fc14de..24a9586 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -632,7 +632,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, 
__u64 orig_blk,
 
                ret = get_ext_path(orig_inode, o_start, &path);
                if (ret)
-                       goto out;
+                       break;
                ex = path[path->p_depth].p_ext;
                next_blk = ext4_ext_next_allocated_block(path);
                cur_blk = le32_to_cpu(ex->ee_block);
@@ -642,7 +642,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, 
__u64 orig_blk,
                        if (next_blk == EXT_MAX_BLOCKS) {
                                o_start = o_end;
                                ret = -ENODATA;
-                               goto out;
+                               break;
                        }
                        d_start += next_blk - o_start;
                        o_start = next_blk;
@@ -654,7 +654,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, 
__u64 orig_blk,
                        o_start = cur_blk;
                        /* Extent inside requested range ?*/
                        if (cur_blk >= o_end)
-                               goto out;
+                               break;
                } else { /* in_range(o_start, o_blk, o_len) */
                        cur_len += cur_blk - o_start;
                }
@@ -687,17 +687,10 @@ ext4_move_extents(struct file *o_filp, struct file 
*d_filp, __u64 orig_blk,
                        break;
                o_start += cur_len;
                d_start += cur_len;
+               *moved_len += cur_len;
        }
-       *moved_len = o_start - orig_blk;
-       if (*moved_len > len)
-               *moved_len = len;
-
 out:
-       if (*moved_len) {
-               ext4_discard_preallocations(orig_inode);
-               ext4_discard_preallocations(donor_inode);
-       }
-
+       WARN_ON(*moved_len > len);
        ext4_ext_drop_refs(path);
        kfree(path);
        ext4_double_up_write_data_sem(orig_inode, donor_inode);
-- 
2.7.4

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