syzbot

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc6-syzkaller-00180-g83158b21ae9a #0 Not tainted
------------------------------------------------------
kswapd1/82 is trying to acquire lock:
ffff88805444c9b8 (&dqp->q_qlock){+.+.}-{4:4}, at: xfs_dqlock fs/xfs/xfs_dquot.h:131 [inline]
ffff88805444c9b8 (&dqp->q_qlock){+.+.}-{4:4}, at: xfs_qm_dqrele+0xce/0x240 fs/xfs/xfs_dquot.c:1150

but task is already holding lock:
ffffffff8ec3a720 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
ffffffff8ec3a720 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264

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:5851
       __fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3867
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4066 [inline]
       slab_alloc_node mm/slub.c:4144 [inline]
       kmem_cache_alloc_node_noprof+0x48/0x380 mm/slub.c:4216
       __alloc_skb+0x1c3/0x440 net/core/skbuff.c:596
       alloc_skb include/linux/skbuff.h:1331 [inline]
       alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289
       uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
       kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207
       bus_uevent_store+0x116/0x170 drivers/base/bus.c:832
       kernfs_fop_write_iter+0x3a0/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0xacf/0xd10 fs/read_write.c:679
       ksys_write+0x18f/0x2b0 fs/read_write.c:731
       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 (uevent_sock_mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
       kobject_uevent_net_broadcast+0x280/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       loop_set_size drivers/block/loop.c:235 [inline]
       loop_set_status+0x4f8/0x800 drivers/block/loop.c:1292
       lo_ioctl+0xce6/0x2870
       blkdev_ioctl+0x5d0/0x6f0 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

-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       bio_queue_enter block/blk.h:78 [inline]
       blk_mq_submit_bio+0x14e1/0x25d0 block/blk-mq.c:3091
       __submit_bio+0x2cf/0x6a0 block/blk-core.c:628
       __submit_bio_noacct_mq block/blk-core.c:715 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:744
       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:2864 [inline]
       xfs_log_force+0x616/0x960 fs/xfs/xfs_log.c:2941
       xfs_qm_dqflush+0x9ae/0x1130 fs/xfs/xfs_dquot.c:1463
       xfs_qm_flush_one+0x295/0x490 fs/xfs/xfs_qm.c:1537
       xfs_qm_dquot_walk+0x232/0x4a0 fs/xfs/xfs_qm.c:90
       xfs_qm_quotacheck+0x357/0x6f0 fs/xfs/xfs_qm.c:1615
       xfs_qm_mount_quotas+0x38f/0x680 fs/xfs/xfs_qm.c:1739
       xfs_mountfs+0x1f3d/0x2500 fs/xfs/xfs_mount.c:1041
       xfs_fs_fill_super+0x1223/0x1550 fs/xfs/xfs_super.c:1817
       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:3560
       do_mount fs/namespace.c:3900 [inline]
       __do_sys_mount fs/namespace.c:4111 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
       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

-> #0 (&dqp->q_qlock){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       xfs_dqlock fs/xfs/xfs_dquot.h:131 [inline]
       xfs_qm_dqrele+0xce/0x240 fs/xfs/xfs_dquot.c:1150
       xfs_qm_dqdetach+0x1a5/0x3e0 fs/xfs/xfs_qm.c:440
       xfs_inode_mark_reclaimable+0x276/0xf40 fs/xfs/xfs_icache.c:2253
       destroy_inode fs/inode.c:386 [inline]
       evict+0x7af/0x9a0 fs/inode.c:827
       dispose_list fs/inode.c:845 [inline]
       prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
       super_cache_scan+0x38c/0x4b0 fs/super.c:223
       do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
       shrink_one+0x43b/0x850 mm/vmscan.c:4868
       shrink_many mm/vmscan.c:4929 [inline]
       lru_gen_shrink_node mm/vmscan.c:5007 [inline]
       shrink_node+0x379b/0x3e20 mm/vmscan.c:5978
       kswapd_shrink_node mm/vmscan.c:6807 [inline]
       balance_pgdat mm/vmscan.c:6999 [inline]
       kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
       kthread+0x7a9/0x920 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Chain exists of:
  &dqp->q_qlock --> uevent_sock_mutex --> fs_reclaim

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(uevent_sock_mutex);
                               lock(fs_reclaim);
  lock(&dqp->q_qlock);

 *** DEADLOCK ***

2 locks held by kswapd1/82:
 #0: ffffffff8ec3a720 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
 #0: ffffffff8ec3a720 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264
 #1: ffff8880426440e0 (&type->s_umount_key#70){++++}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff8880426440e0 (&type->s_umount_key#70){++++}-{4:4}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 82 Comm: kswapd1 Not tainted 6.14.0-rc6-syzkaller-00180-g83158b21ae9a #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:2076
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
 xfs_dqlock fs/xfs/xfs_dquot.h:131 [inline]
 xfs_qm_dqrele+0xce/0x240 fs/xfs/xfs_dquot.c:1150
 xfs_qm_dqdetach+0x1a5/0x3e0 fs/xfs/xfs_qm.c:440
 xfs_inode_mark_reclaimable+0x276/0xf40 fs/xfs/xfs_icache.c:2253
 destroy_inode fs/inode.c:386 [inline]
 evict+0x7af/0x9a0 fs/inode.c:827
 dispose_list fs/inode.c:845 [inline]
 prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
 super_cache_scan+0x38c/0x4b0 fs/super.c:223
 do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
 shrink_one+0x43b/0x850 mm/vmscan.c:4868
 shrink_many mm/vmscan.c:4929 [inline]
 lru_gen_shrink_node mm/vmscan.c:5007 [inline]
 shrink_node+0x379b/0x3e20 mm/vmscan.c:5978
 kswapd_shrink_node mm/vmscan.c:6807 [inline]
 balance_pgdat mm/vmscan.c:6999 [inline]
 kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>