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

[Christian Brauner <brauner@kernel.org>]

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.
If this a big problem then we need to change overlayfs to continue
ignoring garbage mount options passed to it during remount.