kworker/dying (7) used greatest stack depth: 13056 bytes left
INFO: task syz-executor2:21949 blocked for more than 140 seconds.
      Not tainted 4.18.0-rc3-next-20180706+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D20160 21949   4450 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2853 [inline]
 __schedule+0x87c/0x1ed0 kernel/sched/core.c:3501
 schedule+0xfb/0x450 kernel/sched/core.c:3545
 io_schedule+0x1c/0x70 kernel/sched/core.c:5168
 wait_on_page_bit_common+0x4ff/0x7a0 mm/filemap.c:1079
 wait_on_page_bit mm/filemap.c:1112 [inline]
 wait_on_page_locked include/linux/pagemap.h:530 [inline]
 wait_on_page_read mm/filemap.c:2668 [inline]
 do_read_cache_page+0x97a/0x13c0 mm/filemap.c:2707
 read_cache_page_gfp+0x6f/0x90 mm/filemap.c:2810
 btrfs_read_disk_super fs/btrfs/volumes.c:1190 [inline]
 btrfs_scan_one_device+0x274/0xbf0 fs/btrfs/volumes.c:1244
 btrfs_mount_root+0xd12/0x1eb0 fs/btrfs/super.c:1569
 legacy_get_tree+0x118/0x440 fs/fs_context.c:659
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1751
 vfs_kern_mount.part.36+0x119/0x190 fs/namespace.c:3191
 vfs_kern_mount+0x4a/0x70 fs/namespace.c:3171
 btrfs_mount+0x4b7/0x217c fs/btrfs/super.c:1671
 legacy_get_tree+0x118/0x440 fs/fs_context.c:659
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1751
 do_new_mount fs/namespace.c:2567 [inline]
 do_mount+0x6c1/0x1fb0 fs/namespace.c:2889
 ksys_mount+0x12d/0x140 fs/namespace.c:3105
 __do_sys_mount fs/namespace.c:3119 [inline]
 __se_sys_mount fs/namespace.c:3116 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3116
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45885a
Code: 48 8b 44 24 28 48 8b 4c 24 10 48 8b 5c 24 38 4c 8b 54 24 40 e9 31 ff ff ff 4c 89 d3 e9 29 ff ff ff 4c 89 4c 24 20 48 89 74 24 <18> 4c 89 1c 24 48 c7 44 24 08 00 00 00 00 e8 33 91 fb ff 48 8b 44 
RSP: 002b:00007fddec453a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fddec453b30 RCX: 000000000045885a
RDX: 00007fddec453ad0 RSI: 0000000020000100 RDI: 00007fddec453af0
RBP: 0000000020000100 R08: 00007fddec453b30 R09: 00007fddec453ad0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000014
R13: 0000000000000000 R14: 00000000004d3e38 R15: 0000000000000005
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 PID: 897 Comm: khungtaskd Not tainted 4.18.0-rc3-next-20180706+ #1
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+0x1c9/0x2b4 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.5+0x19/0xce lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:143 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
 watchdog+0xb39/0x10b0 kernel/hung_task.c:265
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 21960 Comm: loop2 Not tainted 4.18.0-rc3-next-20180706+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:lock_release+0x1/0xa30 kernel/locking/lockdep.c:3933
Code: 00 e9 b4 fa ff ff e8 be b4 5b 00 4c 8d 4d d8 e9 93 fe ff ff e8 b0 b4 5b 00 e9 79 fc ff ff 90 66 2e 0f 1f 84 00 00 00 00 00 55 <48> 89 e5 41 57 41 56 41 55 49 89 fd 41 54 4c 8d 65 d8 53 48 8d 9d 
RSP: 0018:ffff88019d68e5a8 EFLAGS: 00000293
RAX: ffff88019c72a340 RBX: 0000000000000000 RCX: ffffffff819a01ec
RDX: ffffffff819a020d RSI: 0000000000000001 RDI: ffffffff88f92920
RBP: ffff88019d68e970 R08: ffff88019c72a340 R09: ffffed0033ad1cc5
R10: ffffed0033ad1cc5 R11: 0000000000000003 R12: ffff88019d68e948
R13: ffff8801d3da9310 R14: ffffea0006931a40 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000001b9eba000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 find_lock_entry+0xe6/0x8c0 mm/filemap.c:1457
 shmem_getpage_gfp+0x3cd/0x3ec0 mm/shmem.c:1610
 shmem_getpage mm/shmem.c:132 [inline]
 shmem_file_read_iter+0x399/0x1090 mm/shmem.c:2433
 call_read_iter include/linux/fs.h:1816 [inline]
 do_iter_readv_writev+0x790/0xa90 fs/read_write.c:678
 do_iter_read+0x26e/0x650 fs/read_write.c:922
 vfs_iter_read+0x77/0xb0 fs/read_write.c:936
 lo_read_simple drivers/block/loop.c:350 [inline]
 do_req_filebacked drivers/block/loop.c:615 [inline]
 loop_handle_cmd drivers/block/loop.c:1786 [inline]
 loop_queue_work+0x9ce/0x3afc drivers/block/loop.c:1800
 kthread_worker_fn+0x35f/0xa50 kernel/kthread.c:656
 loop_kthread_worker_fn+0x51/0x60 drivers/block/loop.c:892
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.147 msecs