Kernel bug: possible deadlock in xfs_dquot_detach_buf
Subsystem: xfs
Status: fixed

Crash report:
======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc7-syzkaller-00043-g619f0b6fad52 #0 Not tainted
------------------------------------------------------
syz-executor170/5870 is trying to acquire lock:
ffff888029848170 (&lp->qli_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff888029848170 (&lp->qli_lock){+.+.}-{3:3}, at: xfs_dquot_detach_buf+0x2f/0x1b0 fs/xfs/xfs_dquot.c:83

but task is already holding lock:
ffff888033aebe30 (&l->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff888033aebe30 (&l->lock){+.+.}-{3:3}, at: lock_list_lru_of_memcg+0x24c/0x4d0 mm/list_lru.c:77

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&l->lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       spin_lock include/linux/spinlock.h:351 [inline]
       lock_list_lru_of_memcg+0x24c/0x4d0 mm/list_lru.c:77
       list_lru_add+0x59/0x270 mm/list_lru.c:163
       xfs_buf_rele_cached fs/xfs/xfs_buf.c:1106 [inline]
       xfs_buf_rele+0x4ca/0x15b0 fs/xfs/xfs_buf.c:1151
       xfs_imap_lookup+0x26a/0x750 fs/xfs/libxfs/xfs_ialloc.c:2431
       xfs_imap+0x54d/0x1090 fs/xfs/libxfs/xfs_ialloc.c:2514
       xfs_iget_cache_miss fs/xfs/xfs_icache.c:644 [inline]
       xfs_iget+0xaf6/0x2ec0 fs/xfs/xfs_icache.c:806
       xfs_mountfs+0x13df/0x2410 fs/xfs/xfs_mount.c:919
       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:3511
       do_mount fs/namespace.c:3851 [inline]
       __do_sys_mount fs/namespace.c:4061 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4038
       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 (&bch->bc_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       spin_lock include/linux/spinlock.h:351 [inline]
       _atomic_dec_and_lock+0xb8/0x130 lib/dec_and_lock.c:28
       xfs_buf_rele_cached fs/xfs/xfs_buf.c:1085 [inline]
       xfs_buf_rele+0x178/0x15b0 fs/xfs/xfs_buf.c:1151
       xfs_imap_lookup+0x26a/0x750 fs/xfs/libxfs/xfs_ialloc.c:2431
       xfs_imap+0x54d/0x1090 fs/xfs/libxfs/xfs_ialloc.c:2514
       xfs_iget_cache_miss fs/xfs/xfs_icache.c:644 [inline]
       xfs_iget+0xaf6/0x2ec0 fs/xfs/xfs_icache.c:806
       xfs_mountfs+0x13df/0x2410 fs/xfs/xfs_mount.c:919
       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:3511
       do_mount fs/namespace.c:3851 [inline]
       __do_sys_mount fs/namespace.c:4061 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4038
       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 (&bp->b_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       spin_lock include/linux/spinlock.h:351 [inline]
       xfs_buf_rele_cached fs/xfs/xfs_buf.c:1084 [inline]
       xfs_buf_rele+0x164/0x15b0 fs/xfs/xfs_buf.c:1151
       xfs_dquot_attach_buf+0x33e/0x560 fs/xfs/xfs_dquot.c:1346
       xfs_qm_quotacheck_dqadjust+0x13f/0x5e0 fs/xfs/xfs_qm.c:1341
       xfs_qm_dqusage_adjust+0x6a8/0x850 fs/xfs/xfs_qm.c:1464
       xfs_iwalk_ag_recs+0x4e3/0x820 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:3236 [inline]
       process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
       worker_thread+0x870/0xd30 kernel/workqueue.c:3398
       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 (&lp->qli_lock){+.+.}-{3:3}:
       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
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       spin_lock include/linux/spinlock.h:351 [inline]
       xfs_dquot_detach_buf+0x2f/0x1b0 fs/xfs/xfs_dquot.c:83
       xfs_qm_dquot_isolate+0x49d/0x1420 fs/xfs/xfs_qm.c:528
       __list_lru_walk_one+0x170/0x470 mm/list_lru.c:300
       list_lru_walk_one+0x3c/0x50 mm/list_lru.c:337
       list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
       xfs_qm_shrink_scan+0x1e1/0x400 fs/xfs/xfs_qm.c:574
       do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
       drop_slab_node mm/vmscan.c:421 [inline]
       drop_slab+0x142/0x280 mm/vmscan.c:439
       drop_caches_sysctl_handler+0xbc/0x160 fs/drop_caches.c:68
       proc_sys_call_handler+0x5ec/0x920 fs/proc/proc_sysctl.c:601
       iter_file_splice_write+0xbfa/0x1510 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       direct_splice_actor+0x11b/0x220 fs/splice.c:1164
       splice_direct_to_actor+0x586/0xc80 fs/splice.c:1108
       do_splice_direct_actor fs/splice.c:1207 [inline]
       do_splice_direct+0x289/0x3e0 fs/splice.c:1233
       do_sendfile+0x564/0x8a0 fs/read_write.c:1363
       __do_sys_sendfile64 fs/read_write.c:1418 [inline]
       __se_sys_sendfile64+0x100/0x1e0 fs/read_write.c:1410
       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

other info that might help us debug this:

Chain exists of:
  &lp->qli_lock --> &bch->bc_lock --> &l->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&l->lock);
                               lock(&bch->bc_lock);
                               lock(&l->lock);
  lock(&lp->qli_lock);

 *** DEADLOCK ***

3 locks held by syz-executor170/5870:
 #0: ffff888030e86420 (sb_writers#3){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x220 fs/splice.c:1163
 #1: ffff888033aebe30 (&l->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #1: ffff888033aebe30 (&l->lock){+.+.}-{3:3}, at: lock_list_lru_of_memcg+0x24c/0x4d0 mm/list_lru.c:77
 #2: ffff888029848258 (&xfs_dquot_group_class){+.+.}-{4:4}, at: xfs_dqlock_nowait fs/xfs/xfs_dquot.h:126 [inline]
 #2: ffff888029848258 (&xfs_dquot_group_class){+.+.}-{4:4}, at: xfs_qm_dquot_isolate+0x8d/0x1420 fs/xfs/xfs_qm.c:467

stack backtrace:
CPU: 0 UID: 0 PID: 5870 Comm: syz-executor170 Not tainted 6.13.0-rc7-syzkaller-00043-g619f0b6fad52 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 xfs_dquot_detach_buf+0x2f/0x1b0 fs/xfs/xfs_dquot.c:83
 xfs_qm_dquot_isolate+0x49d/0x1420 fs/xfs/xfs_qm.c:528
 __list_lru_walk_one+0x170/0x470 mm/list_lru.c:300
 list_lru_walk_one+0x3c/0x50 mm/list_lru.c:337
 list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
 xfs_qm_shrink_scan+0x1e1/0x400 fs/xfs/xfs_qm.c:574
 do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
 drop_slab_node mm/vmscan.c:421 [inline]
 drop_slab+0x142/0x280 mm/vmscan.c:439
 drop_caches_sysctl_handler+0xbc/0x160 fs/drop_caches.c:68
 proc_sys_call_handler+0x5ec/0x920 fs/proc/proc_sysctl.c:601
 iter_file_splice_write+0xbfa/0x1510 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x11b/0x220 fs/splice.c:1164
 splice_direct_to_actor+0x586/0xc80 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x289/0x3e0 fs/splice.c:1233
 do_sendfile+0x564/0x8a0 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1418 [inline]
 __se_sys_sendfile64+0x100/0x1e0 fs/read_write.c:1410
 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
RIP: 0033:0x7f712c75cec9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff48ecb9a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f712c75cec9
RDX: 0000000020002080 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00000000000f4240 R08: 0000555583186378 R09: 0000555583186378
R10: 000000000000023b R11: 0000000000000246 R12: 000000000000efb4
R13: 00007fff48ecb9e0 R14: 00007fff48ecb9cc R15: 00007f712c7a603b
 </TASK>
syz-executor170 (5870): drop_caches: 2
syz-executor170 (5870): drop_caches: 2