Re: [PATCH] xfs: Prevent mounting with quotas in norecovery if quotacheck is needed

Carlos Maiolino
2025-01-15T06:33:04Z

On Tue, Jan 14, 2025 at 10:24:38PM -0800, Darrick J. Wong wrote:
> On Wed, Jan 15, 2025 at 07:18:32AM +0100, cem@kernel.org wrote:
> > From: Carlos Maiolino <cem@kernel.org>
> >
> > Mounting a filesystem that requires quota state changing will generate a
> > transaction.
> >
> > We already check for a read-only device; we should do that for
> > norecovery too.
> >
> > A quotacheck on a norecovery mount, and with the right log size, will cause
> > the mount process to hang on:
> >
> > [<0>] xlog_grant_head_wait+0x5d/0x2a0 [xfs]
> > [<0>] xlog_grant_head_check+0x112/0x180 [xfs]
> > [<0>] xfs_log_reserve+0xe3/0x260 [xfs]
> > [<0>] xfs_trans_reserve+0x179/0x250 [xfs]
> > [<0>] xfs_trans_alloc+0x101/0x260 [xfs]
> > [<0>] xfs_sync_sb+0x3f/0x80 [xfs]
> > [<0>] xfs_qm_mount_quotas+0xe3/0x2f0 [xfs]
> > [<0>] xfs_mountfs+0x7ad/0xc20 [xfs]
> > [<0>] xfs_fs_fill_super+0x762/0xa50 [xfs]
> > [<0>] get_tree_bdev_flags+0x131/0x1d0
> > [<0>] vfs_get_tree+0x26/0xd0
> > [<0>] vfs_cmd_create+0x59/0xe0
> > [<0>] __do_sys_fsconfig+0x4e3/0x6b0
> > [<0>] do_syscall_64+0x82/0x160
> > [<0>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
> >
> > This is caused by a transaction running with bogus initialized head/tail
> >
> > I initially hit this while running generic/050, with random log
> > sizes, but I managed to reproduce it reliably here with the steps
> > below:
> >
> > mkfs.xfs -f -lsize=1025M -f -b size=4096 -m crc=1,reflink=1,rmapbt=1, -i
> > sparse=1 /dev/vdb2 > /dev/null
> > mount -o usrquota,grpquota,prjquota /dev/vdb2 /mnt
> > xfs_io -x -c 'shutdown -f' /mnt
> > umount /mnt
> > mount -o ro,norecovery,usrquota,grpquota,prjquota /dev/vdb2 /mnt
> >
> > Last mount hangs up
> >
> > Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> > ---
> > fs/xfs/xfs_qm_bhv.c | 12 +++++++-----
> > 1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_qm_bhv.c b/fs/xfs/xfs_qm_bhv.c
> > index 37f1230e7584..eae106ca7e1b 100644
> > --- a/fs/xfs/xfs_qm_bhv.c
> > +++ b/fs/xfs/xfs_qm_bhv.c
> > @@ -97,10 +97,11 @@ xfs_qm_newmount(
> > }
> >
> > /*
> > - * If the device itself is read-only, we can't allow
> > - * the user to change the state of quota on the mount -
> > - * this would generate a transaction on the ro device,
> > - * which would lead to an I/O error and shutdown
> > + * If the device itself is read-only and/or in norecovery
> > + * mode, we can't allow the user to change the state of
> > + * quota on the mount - this would generate a transaction
> > + * on the ro device, which would lead to an I/O error and
> > + * shutdown.
> > */
> >
> > if (((uquotaondisk && !XFS_IS_UQUOTA_ON(mp)) ||
> > @@ -109,7 +110,8 @@ xfs_qm_newmount(
> > (!gquotaondisk && XFS_IS_GQUOTA_ON(mp)) ||
> > (pquotaondisk && !XFS_IS_PQUOTA_ON(mp)) ||
> > (!pquotaondisk && XFS_IS_PQUOTA_ON(mp))) &&
> > - xfs_dev_is_read_only(mp, "changing quota state")) {
> > + (xfs_dev_is_read_only(mp, "changing quota state") ||
> > + xfs_has_norecovery(mp))) {
> > xfs_warn(mp, "please mount with%s%s%s%s.",
> > (!quotaondisk ? "out quota" : ""),
> > (uquotaondisk ? " usrquota" : ""),
>
> The logic seems ok, but (as I mentioned in office hours this morning) I
> wonder if we shouldn't just ignore quota entirely for a norecovery
> mount?

I gave it a thought. It might work, but, if there are no changes to be made, I
don't see a problem in mounting with quotas and let user browse quota data.

>
> I guess for metadir we also could change the message to say "don't mount
> with any quota options" since the quota mount options are persistent now.

No complains about it :)