syzbot

======================================================
WARNING: possible circular locking dependency detected
6.12.0-next-20241119-syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/88 is trying to acquire lock:
ffff8881fb5e5958 (&qinf->qi_tree_lock){+.+.}-{4:4}, at: xfs_qm_dqfree_one+0x66/0x170 fs/xfs/xfs_qm.c:1874

but task is already holding lock:
ffffffff8ea35ae0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6864 [inline]
ffffffff8ea35ae0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7246

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __fs_reclaim_acquire mm/page_alloc.c:3887 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3901
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4055 [inline]
       slab_alloc_node mm/slub.c:4133 [inline]
       __kmalloc_cache_noprof+0x41/0x390 mm/slub.c:4309
       kmalloc_noprof include/linux/slab.h:901 [inline]
       kzalloc_noprof include/linux/slab.h:1037 [inline]
       kobject_uevent_env+0x28b/0x8e0 lib/kobject_uevent.c:540
       loop_set_size drivers/block/loop.c:233 [inline]
       loop_set_status+0x5f0/0x8f0 drivers/block/loop.c:1285
       lo_ioctl+0xcbc/0x1f50
       blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#20){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       bio_queue_enter block/blk.h:75 [inline]
       blk_mq_submit_bio+0x1536/0x23a0 block/blk-mq.c:3092
       __submit_bio+0x2c6/0x560 block/blk-core.c:629
       __submit_bio_noacct_mq block/blk-core.c:710 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:739
       xlog_state_release_iclog+0x41d/0x7b0 fs/xfs/xfs_log.c:567
       xlog_force_iclog fs/xfs/xfs_log.c:802 [inline]
       xlog_force_and_check_iclog fs/xfs/xfs_log.c:2866 [inline]
       xfs_log_force+0x616/0x960 fs/xfs/xfs_log.c:2943
       xfs_qm_dqflush+0xd5e/0x15e0 fs/xfs/xfs_dquot.c:1333
       xfs_qm_flush_one+0x129/0x430 fs/xfs/xfs_qm.c:1489
       xfs_qm_dquot_walk+0x232/0x4a0 fs/xfs/xfs_qm.c:90
       xfs_qm_quotacheck+0x3aa/0x6f0 fs/xfs/xfs_qm.c:1573
       xfs_qm_mount_quotas+0x38f/0x680 fs/xfs/xfs_qm.c:1693
       xfs_mountfs+0x1e60/0x2410 fs/xfs/xfs_mount.c:1030
       xfs_fs_fill_super+0x12db/0x1590 fs/xfs/xfs_super.c:1791
       get_tree_bdev_flags+0x48c/0x5c0 fs/super.c:1636
       vfs_get_tree+0x90/0x2b0 fs/super.c:1814
       do_new_mount+0x2be/0xb40 fs/namespace.c:3507
       do_mount fs/namespace.c:3847 [inline]
       __do_sys_mount fs/namespace.c:4057 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&xfs_dquot_group_class){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       xfs_dqlock fs/xfs/xfs_dquot.h:131 [inline]
       xfs_qm_dqget_cache_insert fs/xfs/xfs_dquot.c:843 [inline]
       xfs_qm_dqget+0x370/0x6f0 fs/xfs/xfs_dquot.c:910
       xfs_qm_quotacheck_dqadjust+0xea/0x5a0 fs/xfs/xfs_qm.c:1297
       xfs_qm_dqusage_adjust+0x6a8/0x850 fs/xfs/xfs_qm.c:1426
       xfs_iwalk_ag_recs+0x4e1/0x820 fs/xfs/xfs_iwalk.c:209
       xfs_iwalk_run_callbacks+0x218/0x470 fs/xfs/xfs_iwalk.c:370
       xfs_iwalk_ag+0xa9a/0xbb0 fs/xfs/xfs_iwalk.c:476
       xfs_iwalk_ag_work+0xfb/0x1b0 fs/xfs/xfs_iwalk.c:625
       xfs_pwork_work+0x7f/0x190 fs/xfs/xfs_pwork.c:47
       process_one_work kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
       worker_thread+0x870/0xd30 kernel/workqueue.c:3391
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (&qinf->qi_tree_lock){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       xfs_qm_dqfree_one+0x66/0x170 fs/xfs/xfs_qm.c:1874
       xfs_qm_shrink_scan+0x33f/0x400 fs/xfs/xfs_qm.c:558
       do_shrink_slab+0x701/0x1160 mm/shrinker.c:437
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
       shrink_one+0x43b/0x850 mm/vmscan.c:4836
       shrink_many mm/vmscan.c:4897 [inline]
       lru_gen_shrink_node mm/vmscan.c:4975 [inline]
       shrink_node+0x37c5/0x3e50 mm/vmscan.c:5956
       kswapd_shrink_node mm/vmscan.c:6785 [inline]
       balance_pgdat mm/vmscan.c:6977 [inline]
       kswapd+0x1ca9/0x3700 mm/vmscan.c:7246
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Chain exists of:
  &qinf->qi_tree_lock --> &q->q_usage_counter(io)#20 --> fs_reclaim

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&q->q_usage_counter(io)#20);
                               lock(fs_reclaim);
  lock(&qinf->qi_tree_lock);

 *** DEADLOCK ***

1 lock held by kswapd0/88:
 #0: ffffffff8ea35ae0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6864 [inline]
 #0: ffffffff8ea35ae0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7246

stack backtrace:
CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Not tainted 6.12.0-next-20241119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
 xfs_qm_dqfree_one+0x66/0x170 fs/xfs/xfs_qm.c:1874
 xfs_qm_shrink_scan+0x33f/0x400 fs/xfs/xfs_qm.c:558
 do_shrink_slab+0x701/0x1160 mm/shrinker.c:437
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
 shrink_one+0x43b/0x850 mm/vmscan.c:4836
 shrink_many mm/vmscan.c:4897 [inline]
 lru_gen_shrink_node mm/vmscan.c:4975 [inline]
 shrink_node+0x37c5/0x3e50 mm/vmscan.c:5956
 kswapd_shrink_node mm/vmscan.c:6785 [inline]
 balance_pgdat mm/vmscan.c:6977 [inline]
 kswapd+0x1ca9/0x3700 mm/vmscan.c:7246
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>