On Fri, Aug 30, 2024 at 03:27:35PM +0200, Amir Goldstein wrote:
> On Tue, Jul 30, 2024 at 6:20 AM Haifeng Xu <haifeng.xu@xxxxxxxxxx> wrote:
> >
> > 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 <haifeng.xu@xxxxxxxxxx>
> > Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> > ---
> > 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.
>
