======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor/5988 is trying to acquire lock:
ffffffff8e046120 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x153/0x610

but task is already holding lock:
ffffffff8e025608 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x286/0x1720

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (pcpu_alloc_mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       pcpu_alloc_noprof+0x286/0x1720
       blk_stat_alloc_callback+0xd5/0x220
       wbt_init+0xa3/0x500
       wbt_enable_default+0x25d/0x350
       blk_register_queue+0x36a/0x3f0
       __add_disk+0x677/0xd50
       add_disk_fwnode+0xfc/0x480
       loop_add+0x7f0/0xad0
       loop_init+0xd9/0x170
       do_one_initcall+0x236/0x820
       do_initcall_level+0x104/0x190
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x334/0x4b0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x4bc/0x870
       ret_from_fork_asm+0x1a/0x30

-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       lock_acquire+0x120/0x360
       blk_alloc_queue+0x538/0x620
       __blk_mq_alloc_disk+0x15c/0x340
       loop_add+0x411/0xad0
       loop_init+0xd9/0x170
       do_one_initcall+0x236/0x820
       do_initcall_level+0x104/0x190
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x334/0x4b0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x4bc/0x870
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       fs_reclaim_acquire+0x72/0x100
       prepare_alloc_pages+0x153/0x610
       __alloc_frozen_pages_noprof+0x123/0x370
       __alloc_pages_noprof+0xa/0x30
       pcpu_populate_chunk+0x182/0xb30
       pcpu_alloc_noprof+0xcbf/0x1720
       xt_percpu_counter_alloc+0x161/0x220
       translate_table+0x1323/0x2040
       ip6t_register_table+0x106/0x7d0
       ip6table_filter_table_init+0x75/0xb0
       xt_find_table_lock+0x30c/0x3e0
       xt_request_find_table_lock+0x26/0x100
       do_ip6t_get_ctl+0x730/0x1180
       nf_getsockopt+0x26e/0x290
       ipv6_getsockopt+0x1ed/0x290
       do_sock_getsockopt+0x372/0x450
       __x64_sys_getsockopt+0x1a5/0x250
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> &q->q_usage_counter(io)#17 --> pcpu_alloc_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(pcpu_alloc_mutex);
                               lock(&q->q_usage_counter(io)#17);
                               lock(pcpu_alloc_mutex);
  lock(fs_reclaim);

 *** DEADLOCK ***

1 lock held by syz-executor/5988:
 #0: ffffffff8e025608 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x286/0x1720

stack backtrace:
CPU: 1 UID: 0 PID: 5988 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 fs_reclaim_acquire+0x72/0x100
 prepare_alloc_pages+0x153/0x610
 __alloc_frozen_pages_noprof+0x123/0x370
 __alloc_pages_noprof+0xa/0x30
 pcpu_populate_chunk+0x182/0xb30
 pcpu_alloc_noprof+0xcbf/0x1720
 xt_percpu_counter_alloc+0x161/0x220
 translate_table+0x1323/0x2040
 ip6t_register_table+0x106/0x7d0
 ip6table_filter_table_init+0x75/0xb0
 xt_find_table_lock+0x30c/0x3e0
 xt_request_find_table_lock+0x26/0x100
 do_ip6t_get_ctl+0x730/0x1180
 nf_getsockopt+0x26e/0x290
 ipv6_getsockopt+0x1ed/0x290
 do_sock_getsockopt+0x372/0x450
 __x64_sys_getsockopt+0x1a5/0x250
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb85019140a
Code: ff c3 66 0f 1f 44 00 00 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb b8 0f 1f 44 00 00 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 c7 c2 a8 ff ff ff f7
RSP: 002b:00007fffbe029728 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fb85019140a
RDX: 0000000000000040 RSI: 0000000000000029 RDI: 0000000000000003
RBP: 0000000000000029 R08: 00007fffbe02974c R09: ffffffffffffff00
R10: 00007fb8503b2ca8 R11: 0000000000000246 R12: 00007fb85021340a
R13: 00007fb8503b4e60 R14: 00007fb8503b2ca8 R15: 00007fb8503b2ca0
 </TASK>