[PATCH] btrfs: fix bytes_may_use leak in move_existing_remap()

[Mark Harmstone <mark@harmstone.com>]

If the call to btrfs_reserve_extent() in move_existing_remap() returns a
smaller extent than we asked for, currently we're not undoing the
bytes_may_use change that we made. Fix this by calling
btrfs_space_info_update_bytes_may_use() again for the difference.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
Fixes: bbea42dfb91f ("btrfs: move existing remaps before relocating block group")
---
 fs/btrfs/relocation.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 1c42c5180bddd5..3d1756b6116246 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4174,6 +4174,12 @@ static int move_existing_remap(struct btrfs_fs_info *fs_info,
 		return ret;
 	}
 
+	if (ins.offset < length) {
+		spin_lock(&sinfo->lock);
+		btrfs_space_info_update_bytes_may_use(sinfo, ins.offset - length);
+		spin_unlock(&sinfo->lock);
+	}
+
 	dest_addr = ins.objectid;
 	dest_length = ins.offset;
 
-- 
2.52.0