mmap_sem: hlock->read=1 count=-4294967295 current=ffff88804e58c340, owner=ffff88804e58c340
------------[ cut here ]------------
downgrading a read lock
WARNING: CPU: 1 PID: 30605 at kernel/locking/lockdep.c:3572 __lock_downgrade kernel/locking/lockdep.c:3572 [inline]
WARNING: CPU: 1 PID: 30605 at kernel/locking/lockdep.c:3572 lock_downgrade+0x35d/0xbe0 kernel/locking/lockdep.c:3835
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 30605 Comm: blkid Not tainted 5.0.0-rc2-next-20190118 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x48 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:__lock_downgrade kernel/locking/lockdep.c:3572 [inline]
RIP: 0010:lock_downgrade+0x35d/0xbe0 kernel/locking/lockdep.c:3835
Code: 4d 8d 58 a0 48 05 a8 00 00 00 49 39 c3 0f 84 fb 01 00 00 4c 8d 5b 20 48 c7 c7 e0 ac 4b 88 4c 89 9d 10 ff ff ff e8 f3 f4 e6 ff <0f> 0b 4c 89 ea 4c 8b 9d 10 ff ff ff 48 b8 00 00 00 00 00 fc ff df
RSP: 0018:ffff88805701fb60 EFLAGS: 00010082
RAX: 0000000000000000 RBX: ffff88804e58cbc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81688856 RDI: 0000000000000006
RBP: ffff88805701fc70 R08: ffff88804e58c340 R09: fffffbfff13333a9
R10: fffffbfff13333a8 R11: ffffffff89999d43 R12: ffff88804e58c340
R13: ffff88805701fbd8 R14: ffff88805701fc48 R15: 0000000000000002
 downgrade_write+0x76/0x270 kernel/locking/rwsem.c:147
 __do_munmap+0xc5a/0xef0 mm/mmap.c:2823
 __vm_munmap+0x139/0x1f0 mm/mmap.c:2848
 __do_sys_munmap mm/mmap.c:2873 [inline]
 __se_sys_munmap mm/mmap.c:2870 [inline]
 __x64_sys_munmap+0x67/0x80 mm/mmap.c:2870
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f01a53f2417
Code: f0 ff ff 73 01 c3 48 8d 0d 8a ad 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 5d ad 20 00 31 d2 48 29 c2 89
RSP: 002b:00007ffe8af51458 EFLAGS: 00000203 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 00007f01a55fd1c8 RCX: 00007f01a53f2417
RDX: 00000000000fad00 RSI: 00000000000033ef RDI: 00007f01a55f5000
RBP: 00007ffe8af515c0 R08: 0000000000000001 R09: 0000000000000007
R10: 00007f01a53eca0b R11: 0000000000000203 R12: 00000000b34c03af
R13: 000003c1b34c03af R14: 000003c1b33e3b5e R15: 00007f01a55f2740
Kernel Offset: disabled
Rebooting in 86400 seconds..