Btrfs: add missing inode item update in fallocate()

If we fallocate(), without the keep size flag, into an area already covered
by an extent previously fallocated, we were updating the inode's i_size but
we weren't updating the inode item in the fs/subvol tree. A following umount
+ mount would result in a loss of the inode's size (and an fsync would miss
too the fact that the inode changed).

Reproducer:

  $ mkfs.btrfs -f /dev/sdd
  $ mount /dev/sdd /mnt
  $ fallocate -n -l 1M /mnt/foobar
  $ fallocate -l 512K /mnt/foobar
  $ umount /mnt
  $ mount /dev/sdd /mnt
  $ od -t x1 /mnt/foobar
  0000000

The expected result is:

  $ od -t x1 /mnt/foobar
  0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  *
  2000000

A test case for fstests follows soon.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 7d4bb3b6fbc23cd8df679dae0b0aa89a1b78c794..150db5e50c2dd7e0836c513af607fba6da65ef2a 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2669,23 +2669,34 @@ static long btrfs_fallocate(struct file *file, int mode,
                                                        1 << inode->i_blkbits,
                                                        offset + len,
                                                        &alloc_hint);
-
-                       if (ret < 0) {
-                               free_extent_map(em);
-                               break;
-                       }
                } else if (actual_end > inode->i_size &&
                           !(mode & FALLOC_FL_KEEP_SIZE)) {
+                       struct btrfs_trans_handle *trans;
+
                        /*
                         * We didn't need to allocate any more space, but we
                         * still extended the size of the file so we need to
-                        * update i_size.
+                        * update i_size and the inode item.
                         */
-                       inode->i_ctime = CURRENT_TIME;
-                       i_size_write(inode, actual_end);
-                       btrfs_ordered_update_i_size(inode, actual_end, NULL);
+                       trans = btrfs_start_transaction(root, 1);
+                       if (IS_ERR(trans)) {
+                               ret = PTR_ERR(trans);
+                       } else {
+                               inode->i_ctime = CURRENT_TIME;
+                               i_size_write(inode, actual_end);
+                               btrfs_ordered_update_i_size(inode, actual_end,
+                                                           NULL);
+                               ret = btrfs_update_inode(trans, root, inode);
+                               if (ret)
+                                       btrfs_end_transaction(trans, root);
+                               else
+                                       ret = btrfs_end_transaction(trans,
+                                                                   root);
+                       }
                }
                free_extent_map(em);
+               if (ret < 0)
+                       break;
 
                cur_offset = last_byte;
                if (cur_offset >= alloc_end) {