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

[cem@kernel.org]

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" : ""),
-- 
2.47.1