[PATCH] xfs: start inodegc after quota initialization

[Pedro Demarchi Gomes <pedrodemargomes@gmail.com>]

When mounting a xfs filesystem with quotas, if an error occurs in xfs_mount
after calling xfs_inodegc_start and before m_quotainfo initialization, the
error path will call xfs_inodegc_flush assuming that m_quotainfo was already
initialized, causing the following error:

[   82.411853][   T23] ==================================================================
[   82.412678][   T23] BUG: KASAN: null-ptr-deref in mutex_lock (./include/linux/instrumented.h:55 ./include/linux/atomic/atomic-instrumented.h:4457 kernel/locking/mutex.c:159 kernel/locking/mutex.c:289)
[   82.413383][   T23] Write of size 8 at addr 0000000000000030 by task kworker/1:0/23
[   82.414187][   T23]
[   82.414450][   T23] CPU: 1 UID: 0 PID: 23 Comm: kworker/1:0 Not tainted 7.0.0-rc5-00051-gbbeb83d3182a #35 PREEMPT(
[   82.414458][   T23] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[   82.414463][   T23] Workqueue: xfs-inodegc/loop0 xfs_inodegc_worker
[   82.414478][   T23] Call Trace:
[   82.414481][   T23]  <TASK>
[   82.414484][   T23]  dump_stack_lvl (lib/dump_stack.c:122)
[   82.414494][   T23]  print_report (mm/kasan/report.c:487)
[   82.414518][   T23]  kasan_report (mm/kasan/report.c:597)
[   82.414541][   T23]  kasan_check_range (mm/kasan/generic.c:? mm/kasan/generic.c:200)
[   82.414549][   T23]  mutex_lock (./include/linux/instrumented.h:55 ./include/linux/atomic/atomic-instrumented.h:4457 kernel/locking/mutex.c:159 kernel/locking/mutex.c:289)
[   82.414601][   T23]  xfs_qm_dqget_cache_lookup (fs/xfs/xfs_dquot.c:813)
[   82.414609][   T23]  xfs_qm_dqget_inode (fs/xfs/xfs_dquot.c:1017)
[   82.414678][   T23]  xfs_qm_dqattach_locked (fs/xfs/xfs_qm.c:331)
[   82.414688][   T23]  xfs_qm_dqattach (fs/xfs/xfs_qm.c:371)
[   82.414696][   T23]  xfs_inactive (fs/xfs/xfs_inode.c:1453)
[   82.414733][   T23]  xfs_inodegc_worker (fs/xfs/xfs_icache.c:1946 fs/xfs/xfs_icache.c:1992)
[   82.414743][   T23]  process_scheduled_works (kernel/workqueue.c:3281 kernel/workqueue.c:3359)
[   82.414755][   T23]  worker_thread (kernel/workqueue.c:?)
[   82.414775][   T23]  kthread (kernel/kthread.c:437)
[   82.414787][   T23]  ret_from_fork (arch/x86/kernel/process.c:164)
[   82.414822][   T23]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
[   82.414834][   T23]  </TASK>

To avoid this, call xfs_inodegc_start after quota initialization.

Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Closes: https://lore.kernel.org/all/DDC07F0C-05D2-46B4-9815-E010749FB3DC@gmail.com/
Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
---
 fs/xfs/xfs_mount.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index ef1ea8a1238c..d6f75ab41337 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1057,7 +1057,6 @@ xfs_mountfs(
 		xfs_clear_using_logged_xattrs(mp);
 
 	/* Enable background inode inactivation workers. */
-	xfs_inodegc_start(mp);
 	xfs_blockgc_start(mp);
 
 	if (xfs_has_metadir(mp)) {
@@ -1143,6 +1142,8 @@ xfs_mountfs(
 		}
 	}
 
+	xfs_inodegc_start(mp);
+
 	/*
 	 * Finish recovering the file system.  This part needed to be delayed
 	 * until after the root and real-time bitmap inodes were consistently
-- 
2.47.3