INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 11935 Comm: syz-executor2 Not tainted 4.15.0-rc3-next-20171214+ #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xe9/0x14b lib/dump_stack.c:53
 register_lock_class+0x164/0x5d0 kernel/locking/lockdep.c:752
 __lock_acquire+0xb4/0x1430 kernel/locking/lockdep.c:3314
 lock_acquire+0xbf/0x220 kernel/locking/lockdep.c:3914
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
 spin_lock include/linux/spinlock.h:310 [inline]
 blk_mq_sched_dispatch_requests+0x9d/0x1f0 block/blk-mq-sched.c:194
 __blk_mq_run_hw_queue+0x160/0x220 block/blk-mq.c:1219
 __blk_mq_delay_run_hw_queue+0xdd/0xf0 block/blk-mq.c:1267
 blk_mq_run_hw_queue+0x36/0xa0 block/blk-mq.c:1289
 blk_mq_run_hw_queues+0x51/0x80 block/blk-mq.c:1306
 blk_freeze_queue_start+0x52/0x60 block/blk-mq.c:130
 blk_set_queue_dying+0x57/0x130 block/blk-core.c:630
 blk_cleanup_queue+0x33/0x2d0 block/blk-core.c:665
 loop_remove+0x19/0x50 drivers/block/loop.c:1861
 loop_control_ioctl+0x19a/0x1a0 drivers/block/loop.c:1960
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0xaf/0x840 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x7f/0x270 arch/x86/entry/common.c:285
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x452a09
RSP: 002b:00007fc8e8025c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452a09
RDX: ffffffffffffffff RSI: 0000000000004c81 RDI: 0000000000000014
RBP: 000000000000024b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f07a8
R13: 00000000ffffffff R14: 00007fc8e80266d4 R15: 0000000000000000
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: list_splice_init include/linux/list.h:337 [inline]
IP: blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196
PGD 1fa723067 P4D 1fa723067 PUD 20d6c6067 PMD 0 
Oops: 0002 [#1] SMP
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 11935 Comm: syz-executor2 Not tainted 4.15.0-rc3-next-20171214+ #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:list_splice_init include/linux/list.h:337 [inline]
RIP: 0010:blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196
RSP: 0018:ffffc90000e2bcc0 EFLAGS: 00010246
RAX: ffffc90000e2bcc0 RBX: ffff8801fc5de800 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffc90004a50000 RDI: ffff8801fc5de800
RBP: ffffc90000e2bcf8 R08: 0000000000000000 R09: ffffffff816fdf9d
R10: ffffc90000e2bc30 R11: 0000000000000000 R12: ffffc90000e2bcc0
R13: ffff8801fc5de838 R14: ffff880215626040 R15: 0000000000000001
FS:  00007fc8e8026700(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 00000001fa74f006 CR4: 00000000001626e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 __blk_mq_run_hw_queue+0x160/0x220 block/blk-mq.c:1219
 __blk_mq_delay_run_hw_queue+0xdd/0xf0 block/blk-mq.c:1267
 blk_mq_run_hw_queue+0x36/0xa0 block/blk-mq.c:1289
 blk_mq_run_hw_queues+0x51/0x80 block/blk-mq.c:1306
 blk_freeze_queue_start+0x52/0x60 block/blk-mq.c:130
 blk_set_queue_dying+0x57/0x130 block/blk-core.c:630
 blk_cleanup_queue+0x33/0x2d0 block/blk-core.c:665
 loop_remove+0x19/0x50 drivers/block/loop.c:1861
 loop_control_ioctl+0x19a/0x1a0 drivers/block/loop.c:1960
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0xaf/0x840 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x7f/0x270 arch/x86/entry/common.c:285
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x452a09
RSP: 002b:00007fc8e8025c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452a09
RDX: ffffffffffffffff RSI: 0000000000004c81 RDI: 0000000000000014
RBP: 000000000000024b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f07a8
R13: 00000000ffffffff R14: 00007fc8e80266d4 R15: 0000000000000000
Code: 24 ed 00 48 8b 43 38 49 39 c5 74 36 e8 95 c3 bb ff 48 8b 43 38 49 39 c5 74 28 e8 87 c3 bb ff 48 8b 4b 38 48 8b 53 40 48 8b 45 c8 <4c> 89 61 08 48 89 4d c8 48 89 02 48 89 50 08 4c 89 6b 38 4c 89 
RIP: list_splice_init include/linux/list.h:337 [inline] RSP: ffffc90000e2bcc0
RIP: blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196 RSP: ffffc90000e2bcc0
CR2: 0000000000000008
---[ end trace a04ca4b5c7884582 ]---