generic/335: explicitly fsync file foo when running on btrfs

The test is relying on the fact that an fsync on directory "a" will
result in persisting the changes of its subdirectory "b", namely the
rename of "/a/b/foo" to "/c/foo". For this particular filesystem layout,
that will happen on btrfs, because all the directory entries end up in
the same metadata leaf. However that is not a behaviour we can always
guarantee on btrfs. For example, if we add more files to directory
"a" before and after creating subdirectory "b", like this:

  mkdir $SCRATCH_MNT/a
  for ((i = 0; i < 1000; i++)); do
      echo -n > $SCRATCH_MNT/a/file_$i
  done
  mkdir $SCRATCH_MNT/a/b
  for ((i = 1000; i < 2000; i++)); do
      echo -n > $SCRATCH_MNT/a/file_$i
  done
  mkdir $SCRATCH_MNT/c
  touch $SCRATCH_MNT/a/b/foo

  sync

  # The rest of the test remains unchanged...
  (...)

Then after fsyncing only directory "a", the rename of file "foo" from
"/a/b/foo" to "/c/foo" is not persisted.

Guaranteeing that on btrfs would be expensive on large directories, as
it would require scanning for every subdirectory. It's also not required
by posix for the fsync on a directory to persist changes inside its
subdirectories. So add an explicit fsync on file "foo" when the filesystem
being tested is btrfs.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/generic/335 b/tests/generic/335
index e04f7a5f15..196ada6414 100755
--- a/tests/generic/335
+++ b/tests/generic/335
@@ -51,6 +51,15 @@ mv $SCRATCH_MNT/a/b/foo $SCRATCH_MNT/c/
 touch $SCRATCH_MNT/a/bar
 $XFS_IO_PROG -c "fsync" $SCRATCH_MNT/a
 
+# btrfs can not guarantee that when we fsync a directory all its subdirectories
+# created on past transactions are fsynced as well. It may do it sometimes, but
+# it's not guaranteed, giving such guarantees would be too expensive for large
+# directories and posix does not require that recursive behaviour. So if we want
+# the rename of "foo" to be persisted, explicitly fsync "foo".
+if [ $FSTYP == "btrfs" ]; then
+	$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/c/foo
+fi
+
 echo "Filesystem content before power failure:"
 ls -R $SCRATCH_MNT/a $SCRATCH_MNT/c | _filter_scratch