====================================================== WARNING: possible circular locking dependency detected 6.16.0-syzkaller-08685-g260f6f4fda93 #0 Not tainted ------------------------------------------------------ syz.1.436/7927 is trying to acquire lock: ffff888142f12d28 (&q->elevator_lock){+.+.}-{4:4}, at: elevator_change+0x103/0x400 block/elevator.c:677 but task is already holding lock: ffff888142f127e8 (&q->q_usage_counter(io)#18){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&q->q_usage_counter(io)#18){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4400 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4447 loop_add+0x490/0xb70 drivers/block/loop.c:2034 loop_init+0x164/0x270 drivers/block/loop.c:2269 do_one_initcall+0x120/0x6e0 init/main.c:1269 do_initcall_level init/main.c:1331 [inline] do_initcalls init/main.c:1347 [inline] do_basic_setup init/main.c:1366 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1579 kernel_init+0x1c/0x2b0 init/main.c:1469 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (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 bpf_map_alloc_percpu+0x9a/0x4b0 kernel/bpf/syscall.c:556 prealloc_init kernel/bpf/hashtab.c:336 [inline] htab_map_alloc+0x10ca/0x1570 kernel/bpf/hashtab.c:561 map_create+0x592/0x1db0 kernel/bpf/syscall.c:1477 __sys_bpf+0x44d2/0x4de0 kernel/bpf/syscall.c:6004 __do_sys_bpf kernel/bpf/syscall.c:6132 [inline] __se_sys_bpf kernel/bpf/syscall.c:6130 [inline] __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:6130 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (pcpu_alloc_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x191/0x1070 kernel/locking/mutex.c:760 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:3542 [inline] blk_mq_alloc_map_and_rqs+0x237/0xf60 block/blk-mq.c:4098 blk_mq_sched_alloc_map_and_rqs block/blk-mq-sched.c:386 [inline] blk_mq_init_sched+0x30c/0x610 block/blk-mq-sched.c:485 elevator_switch+0x1e1/0x7f0 block/elevator.c:595 elevator_change+0x2ac/0x400 block/elevator.c:679 elevator_set_default+0x2c4/0x360 block/elevator.c:742 blk_register_queue+0x393/0x4f0 block/blk-sysfs.c:905 __add_disk+0x74a/0xf00 block/genhd.c:528 add_disk_fwnode+0x13f/0x5d0 block/genhd.c:597 add_disk include/linux/blkdev.h:773 [inline] nbd_dev_add+0x783/0xbb0 drivers/block/nbd.c:1973 nbd_init+0x181/0x320 drivers/block/nbd.c:2680 do_one_initcall+0x120/0x6e0 init/main.c:1269 do_initcall_level init/main.c:1331 [inline] do_initcalls init/main.c:1347 [inline] do_basic_setup init/main.c:1366 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1579 kernel_init+0x1c/0x2b0 init/main.c:1469 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&q->elevator_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x191/0x1070 kernel/locking/mutex.c:760 elevator_change+0x103/0x400 block/elevator.c:677 elv_iosched_store+0x2eb/0x3a0 block/elevator.c:799 queue_attr_store+0x268/0x310 block/blk-sysfs.c:831 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 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: &q->elevator_lock --> fs_reclaim --> &q->q_usage_counter(io)#18 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#18); lock(fs_reclaim); lock(&q->q_usage_counter(io)#18); lock(&q->elevator_lock); *** DEADLOCK *** 7 locks held by syz.1.436/7927: #0: ffff88807a144d38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1232 #1: ffff88807d91a428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738 #2: ffff888031aafc88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325 #3: ffff88802612ce18 (kn->active#114){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326 #4: ffff888142f6e368 (&set->update_nr_hwq_lock){.+.+}-{4:4}, at: elv_iosched_store+0x337/0x3a0 block/elevator.c:797 #5: ffff888142f127e8 (&q->q_usage_counter(io)#18){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #6: ffff888142f12820 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 stack backtrace: CPU: 0 UID: 0 PID: 7927 Comm: syz.1.436 Not tainted 6.16.0-syzkaller-08685-g260f6f4fda93 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 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:2043 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x191/0x1070 kernel/locking/mutex.c:760 elevator_change+0x103/0x400 block/elevator.c:677 elv_iosched_store+0x2eb/0x3a0 block/elevator.c:799 queue_attr_store+0x268/0x310 block/blk-sysfs.c:831 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f65e498eb69 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:00007f65e5834038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f65e4bb6080 RCX: 00007f65e498eb69 RDX: 000000000000ffd8 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f65e4a11df1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f65e4bb6080 R15: 00007fff040b8f88