xfs: test COW writeback failure when overlapping non-shared blocks

xfs: test COW writeback failure when overlapping non-shared blocks

Test that COW writeback that overlaps non-shared delalloc blocks
does not leave around stale delalloc blocks on I/O failure. This
triggers assert failures and free space accounting corruption on
XFS.

Fixed by upstream kernel commit 5ca5916b6bc9 ("xfs: punch out data
fork delalloc blocks on COW writeback failure").

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>