============================================
WARNING: possible recursive locking detected
4.14.0-next-20171121+ #48 Not tainted
--------------------------------------------
syz-executor0/7574 is trying to acquire lock:
 (&q->blk_trace_mutex){+.+.}, at: [<ffffffff81768591>] blk_trace_remove+0x21/0x40 kernel/trace/blktrace.c:373

but task is already holding lock:
 (&q->blk_trace_mutex){+.+.}, at: [<ffffffff8176be68>] blk_trace_setup+0x38/0x70 kernel/trace/blktrace.c:606

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&q->blk_trace_mutex);
  lock(&q->blk_trace_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor0/7574:
 #0:  (&q->blk_trace_mutex){+.+.}, at: [<ffffffff8176be68>] blk_trace_setup+0x38/0x70 kernel/trace/blktrace.c:606

stack backtrace:
CPU: 0 PID: 7574 Comm: syz-executor0 Not tainted 4.14.0-next-20171121+ #48
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+0x194/0x257 lib/dump_stack.c:53
 print_deadlock_bug kernel/locking/lockdep.c:1809 [inline]
 check_deadlock kernel/locking/lockdep.c:1856 [inline]
 validate_chain kernel/locking/lockdep.c:2457 [inline]
 __lock_acquire+0x11cf/0x47f0 kernel/locking/lockdep.c:3500
 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
 blk_trace_remove+0x21/0x40 kernel/trace/blktrace.c:373
 __blk_trace_setup+0x12b/0x140 kernel/trace/blktrace.c:594
 blk_trace_setup+0x4d/0x70 kernel/trace/blktrace.c:607
 sg_ioctl+0xc77/0x2da0 drivers/scsi/sg.c:1089
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452879
RSP: 002b:00007ff0d3093be8 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452879
RDX: 0000000020820f90 RSI: 00000000c0481273 RDI: 0000000000000013
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ed280
R13: 00000000ffffffff R14: 00007ff0d30946d4 R15: 0000000000000000
netlink: 2 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 2 bytes leftover after parsing attributes in process `syz-executor0'.
device gre0 entered promiscuous mode