Re: lots of fstests cases fail on overlay with util-linux 2.40.2 (new mount APIs)

[Dave Chinner <david@fromorbit.com>]

On Tue, Oct 29, 2024 at 03:28:04AM +0800, Zorro Lang wrote:
> On Mon, Oct 28, 2024 at 01:22:52PM +0100, Christian Brauner wrote:
> > On Sun, Oct 27, 2024 at 02:07:41AM +0800, Zorro Lang wrote:
> > > Hi,
> > > 
> > > Recently, I hit lots of fstests cases fail on overlayfs (xfs underlying, no
> > > specific mount options), e.g.
> > > 
> > > FSTYP         -- overlay
> > > PLATFORM      -- Linux/s390x s390x-xxxx 6.12.0-rc4+ #1 SMP Fri Oct 25 14:29:18 EDT 2024
> > > MKFS_OPTIONS  -- -m crc=1,finobt=1,rmapbt=0,reflink=1,inobtcount=1,bigtime=1 /mnt/fstests/SCRATCH_DIR
> > > MOUNT_OPTIONS -- -o context=system_u:object_r:root_t:s0 /mnt/fstests/SCRATCH_DIR /mnt/fstests/SCRATCH_DIR/ovl-mnt
> > > 
> > > generic/294       [failed, exit status 1]- output mismatch (see /var/lib/xfstests/results//generic/294.out.bad)
> > >     --- tests/generic/294.out	2024-10-25 14:38:32.098692473 -0400
> > >     +++ /var/lib/xfstests/results//generic/294.out.bad	2024-10-25 15:02:34.698605062 -0400
> > >     @@ -1,5 +1,5 @@
> > >      QA output created by 294
> > >     -mknod: SCRATCH_MNT/294.test/testnode: File exists
> > >     -mkdir: cannot create directory 'SCRATCH_MNT/294.test/testdir': File exists
> > >     -touch: cannot touch 'SCRATCH_MNT/294.test/testtarget': Read-only file system
> > >     -ln: creating symbolic link 'SCRATCH_MNT/294.test/testlink': File exists
> > >     +mount: /mnt/fstests/SCRATCH_DIR/ovl-mnt: fsconfig system call failed: overlay: No changes allowed in reconfigure.
> > >     +       dmesg(1) may have more information after failed mount system call.
> > 
> > In the new mount api overlayfs has been changed to reject invalid mount
> > option on remount whereas in the old mount api we just igorned them.
> 
> Not only g/294 fails on new mount utils, not sure if all of them are from same issue.
> If you need, I can paste all test failures (only from my side) at here.
> 
> > If this a big problem then we need to change overlayfs to continue
> > ignoring garbage mount options passed to it during remount.
> 
> Do you mean this behavior change is only for overlayfs, doesn't affect other fs?

We tried this with XFS years ago, and reverted back to the old
behaviour of silently ignoring mount options we don't support in
remount. The filesystem code has no idea what mount API
userspace is using for remount - it can't assume that it is ok to
error out on unknown/unsupported options because it uses
the fsreconfigure API internally....

-Dave.
-- 
Dave Chinner
david@fromorbit.com