INFO: task hung in blkdev_issue_flush

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 5d8bfdf8 UPSTREAM: drm/virtio: Fix cache entry creation ra..
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=111888f2600000
kernel config: https://syzkaller.appspot.com/x/.config?x=ebced6c15132b98
dashboard link: https://syzkaller.appspot.com/bug?extid=fc971f41032890c4bc4d
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fc971f...@syzkaller.appspotmail.com

INFO: task loop2:20243 blocked for more than 140 seconds.
Not tainted 4.14.139+ #34
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
loop2 D29040 20243 2 0x80000000
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_timeout+0x752/0xe90 kernel/time/timer.c:1721
io_schedule_timeout+0x26/0x80 kernel/sched/core.c:5091
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common_io.constprop.0+0x274/0x3b0 kernel/sched/completion.c:129
submit_bio_wait+0x107/0x170 block/bio.c:1013
blkdev_issue_flush+0x218/0x320 block/blk-flush.c:531
blkdev_fsync+0x80/0xb0 fs/block_dev.c:659
vfs_fsync_range+0x106/0x260 fs/sync.c:196
lo_req_flush drivers/block/loop.c:444 [inline]
do_req_filebacked drivers/block/loop.c:567 [inline]
loop_handle_cmd drivers/block/loop.c:1768 [inline]
loop_queue_work+0xbe5/0x1deb drivers/block/loop.c:1782
kthread_worker_fn+0x28f/0x6d0 kernel/kthread.c:642
kthread+0x31f/0x430 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404
INFO: task syz-executor.5:26237 blocked for more than 140 seconds.
Not tainted 4.14.139+ #34
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D28912 26237 1842 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_timeout+0x752/0xe90 kernel/time/timer.c:1721
io_schedule_timeout+0x26/0x80 kernel/sched/core.c:5091
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common_io.constprop.0+0x274/0x3b0 kernel/sched/completion.c:129
submit_bio_wait+0x107/0x170 block/bio.c:1013
blkdev_issue_flush+0x218/0x320 block/blk-flush.c:531
blkdev_fsync+0x80/0xb0 fs/block_dev.c:659
vfs_fsync_range+0x106/0x260 fs/sync.c:196
vfs_fsync fs/sync.c:210 [inline]
do_fsync+0x3d/0xb0 fs/sync.c:220
SYSC_fdatasync fs/sync.c:234 [inline]
SyS_fdatasync+0x15/0x20 fs/sync.c:232
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459829
RSP: 002b:00007f1e32627c78 EFLAGS: 00000246 ORIG_RAX: 000000000000004b
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1e326286d4
R13: 00000000004c00c7 R14: 00000000004d2190 R15: 00000000ffffffff
INFO: task syz-executor.5:26310 blocked for more than 140 seconds.
Not tainted 4.14.139+ #34
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29232 26310 1842 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_timeout+0x752/0xe90 kernel/time/timer.c:1721
io_schedule_timeout+0x26/0x80 kernel/sched/core.c:5091
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common_io.constprop.0+0x274/0x3b0 kernel/sched/completion.c:129
submit_bio_wait+0x107/0x170 block/bio.c:1013
blkdev_issue_flush+0x218/0x320 block/blk-flush.c:531
blkdev_fsync+0x80/0xb0 fs/block_dev.c:659
vfs_fsync_range+0x106/0x260 fs/sync.c:196
vfs_fsync fs/sync.c:210 [inline]
do_fsync+0x3d/0xb0 fs/sync.c:220
SYSC_fdatasync fs/sync.c:234 [inline]
SyS_fdatasync+0x15/0x20 fs/sync.c:232
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459829
RSP: 002b:00007f1e325e5c78 EFLAGS: 00000246 ORIG_RAX: 000000000000004b
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1e325e66d4
R13: 00000000004c00c7 R14: 00000000004d2190 R15: 00000000ffffffff

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<000000002d150a49>]
debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4541
2 locks held by getty/1754:
#0: (&tty->ldisc_sem){++++}, at: [<0000000035acf7d3>]
tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000658acbf2>]
n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 23 Comm: khungtaskd Not tainted 4.14.139+ #34
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xca/0x134 lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x119/0x147 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x629/0xbe0 kernel/hung_task.c:274
kthread+0x31f/0x430 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffffbc899443


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.