On Fri, Aug 30, 2024 at 03:27:35PM +0200, Amir Goldstein wrote:

On Tue, Jul 30, 2024 at 6:20 AM Haifeng Xu [off-list ref] wrote:

quoted

Since commit 5679897eb104 ("vfs: make sync_filesystem return errors from
->sync_fs"), the return value from sync_fs callback can be seen in
sync_filesystem(). Thus the errseq_set opreation can be removed here.

Depends-on: commit 5679897eb104 ("vfs: make sync_filesystem return errors from ->sync_fs")
Signed-off-by: Haifeng Xu <redacted>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
---
Changes since v1:
- Add Depends-on and Reviewed-by tags.
---
 fs/overlayfs/super.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 06a231970cb5..fe511192f83c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c

@@ -202,15 +202,9 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
        int ret;

        ret = ovl_sync_status(ofs);
-       /*
-        * We have to always set the err, because the return value isn't
-        * checked in syncfs, and instead indirectly return an error via
-        * the sb's writeback errseq, which VFS inspects after this call.
-        */
-       if (ret < 0) {
-               errseq_set(&sb->s_wb_err, -EIO);
+
+       if (ret < 0)
                return -EIO;
-       }

        if (!ret)
                return ret;
--

2.25.1

FYI, this change is queued in overlayfs-next.

However, I went to see if overlayfs has test coverage for this and it does not.

The test coverage added by Darrick to the mentioned vfs commit is test xfs/546,
so it does not run on other fs, although it is quite generic.

I fixed this test so it could run on overlayfs (like this):
# This command is complicated a bit because in the case of overlayfs the
# syncfs fd needs to be opened before shutdown and it is different from the
# shutdown fd, so we cannot use the _scratch_shutdown() helper.
# Filter out xfs_io output of active fds.
$XFS_IO_PROG -x -c "open $(_scratch_shutdown_handle)" -c 'shutdown -f
' -c close -c syncfs $SCRATCH_MNT | \
        grep -vF '[00'

and it passes on both xfs and overlayfs (over xfs), but if I try to
make it "generic"
it fails on ext4, which explicitly allows syncfs after shutdown:

        if (unlikely(ext4_forced_shutdown(sb)))
                return 0;

Ted, Darrick,

Do you have any insight as to why this ext4 behavior differs from xfs
or another idea how to exercise the syncfs error in a generic test?

I could fork an overlay/* test from the xfs/* test and require that
underlying fs is xfs, but that would be ugly.

Any ideas?

That should be:

	if (unlikely(ext4_forced_shutdown(sb)))
		return -EIO;

no?  The fs is dead and cannot persist anything, so we should fling that
back to the calling program.

--D

Thanks,
Amir.