Btrfs: fix wrong nbytes information of the inode

If we write some data into the data hole of the file(no preallocation for this hole), Btrfs will allocate some disk space, and update nbytes of the inode, but the other element--disk_i_size needn't be updated. At this condition, we must update inode metadata though disk_i_size is not changed(btrfs_ordered_update_i_size() return 1).

 # mkfs.btrfs /dev/sdb1
 # mount /dev/sdb1 /mnt
 # touch /mnt/a
 # truncate -s 856002 /mnt/a
 # dd if=/dev/zero of=/mnt/a bs=4K count=1 conv=nocreat,notrunc
 # umount /mnt
 # btrfsck /dev/sdb1
 root 5 inode 257 errors 400
 found 32768 bytes used err is 1

Signed-off-by Miao Xie <[email protected]>

---
 fs/btrfs/inode.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

fs/btrfs/inode.c +2 -2

index 18d08f4..634dd797 100644
@@ -1786,7 +1786,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
 			  &ordered_extent->list);
 
 	ret = btrfs_ordered_update_i_size(inode, 0, ordered_extent);
-	if (!ret) {
+	if (!ret || !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
 		ret = btrfs_update_inode(trans, root, inode);
 		BUG_ON(ret);
 	}

@@ -5788,7 +5788,7 @@ again:
 
 	add_pending_csums(trans, inode, ordered->file_offset, &ordered->list);
 	ret = btrfs_ordered_update_i_size(inode, 0, ordered);
-	if (!ret)
+	if (!ret || !test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags))
 		btrfs_update_inode(trans, root, inode);
 	ret = 0;
 out_unlock: