====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-00236-g8c6bc74c7f89 #0 Not tainted ------------------------------------------------------ syz.3.1174/10935 is trying to acquire lock: ffffffff8e72fa68 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 but task is already holding lock: ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:4993 [inline] ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: blk_mq_update_nr_hw_queues+0x275/0xcb0 block/blk-mq.c:5043 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#52){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x175/0x290 block/blk-mq.c:4396 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4443 nbd_dev_add+0x4a0/0xbc0 drivers/block/nbd.c:1933 nbd_init+0x181/0x320 drivers/block/nbd.c:2670 do_one_initcall+0x120/0x6e0 init/main.c:1274 do_initcall_level init/main.c:1336 [inline] do_initcalls init/main.c:1352 [inline] do_basic_setup init/main.c:1371 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1584 kernel_init+0x1c/0x2b0 init/main.c:1474 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4059 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4727 __alloc_frozen_pages_noprof+0x18b/0x23f0 mm/page_alloc.c:4948 __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:4993 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline] alloc_pages_node_noprof include/linux/gfp.h:311 [inline] pcpu_alloc_pages mm/percpu-vm.c:95 [inline] pcpu_populate_chunk+0x110/0xb00 mm/percpu-vm.c:285 pcpu_alloc_noprof+0x86a/0x1470 mm/percpu.c:1870 mem_cgroup_alloc mm/memcontrol.c:3732 [inline] mem_cgroup_css_alloc+0x87b/0x1e80 mm/memcontrol.c:3791 css_create kernel/cgroup/cgroup.c:5664 [inline] cgroup_apply_control_enable+0x4ad/0xbb0 kernel/cgroup/cgroup.c:3284 cgroup_mkdir+0x5e7/0x11f0 kernel/cgroup/cgroup.c:5888 kernfs_iop_mkdir+0x111/0x190 fs/kernfs/dir.c:1268 vfs_mkdir+0x590/0x8c0 fs/namei.c:4366 do_mkdirat+0x304/0x3e0 fs/namei.c:4399 __do_sys_mkdirat fs/namei.c:4416 [inline] __se_sys_mkdirat fs/namei.c:4414 [inline] __x64_sys_mkdirat+0x83/0xb0 fs/namei.c:4414 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (pcpu_alloc_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2fd/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x41/0x560 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x12d/0x2b0 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0x237/0xf60 block/blk-mq.c:4094 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4116 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4107 blk_mq_realloc_tag_set_tags block/blk-mq.c:4755 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4995 [inline] blk_mq_update_nr_hw_queues+0x4ab/0xcb0 block/blk-mq.c:5043 nbd_start_device+0x172/0xcd0 drivers/block/nbd.c:1476 nbd_start_device_ioctl drivers/block/nbd.c:1527 [inline] __nbd_ioctl drivers/block/nbd.c:1602 [inline] nbd_ioctl+0x219/0xda0 drivers/block/nbd.c:1642 blkdev_ioctl+0x277/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: pcpu_alloc_mutex --> fs_reclaim --> &q->q_usage_counter(io)#52 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#52); lock(fs_reclaim); lock(&q->q_usage_counter(io)#52); lock(pcpu_alloc_mutex); *** DEADLOCK *** 5 locks held by syz.3.1174/10935: #0: ffff888026a85a30 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_ioctl+0x150/0xda0 drivers/block/nbd.c:1635 #1: ffff888026a85988 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x32/0xcb0 block/blk-mq.c:5041 #2: ffff888026a858d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x45/0xcb0 block/blk-mq.c:5042 #3: ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #3: ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:4993 [inline] #3: ffff8880268ce278 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: blk_mq_update_nr_hw_queues+0x275/0xcb0 block/blk-mq.c:5043 #4: ffff8880268ce2b0 (&q->q_usage_counter(queue)#4){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #4: ffff8880268ce2b0 (&q->q_usage_counter(queue)#4){+.+.}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:4993 [inline] #4: ffff8880268ce2b0 (&q->q_usage_counter(queue)#4){+.+.}-{0:0}, at: blk_mq_update_nr_hw_queues+0x275/0xcb0 block/blk-mq.c:5043 stack backtrace: CPU: 0 UID: 0 PID: 10935 Comm: syz.3.1174 Not tainted 6.16.0-rc1-syzkaller-00236-g8c6bc74c7f89 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2fd/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x41/0x560 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x12d/0x2b0 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0x237/0xf60 block/blk-mq.c:4094 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4116 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4107 blk_mq_realloc_tag_set_tags block/blk-mq.c:4755 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4995 [inline] blk_mq_update_nr_hw_queues+0x4ab/0xcb0 block/blk-mq.c:5043 nbd_start_device+0x172/0xcd0 drivers/block/nbd.c:1476 nbd_start_device_ioctl drivers/block/nbd.c:1527 [inline] __nbd_ioctl drivers/block/nbd.c:1602 [inline] nbd_ioctl+0x219/0xda0 drivers/block/nbd.c:1642 blkdev_ioctl+0x277/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd46358e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fd464458038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fd4637b6080 RCX: 00007fd46358e929 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004 RBP: 00007fd463610b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fd4637b6080 R15: 00007ffd1122ab78 block nbd3: shutting down sockets