INFO: task hung in write_cache_pages

[syzbot]

Hello,

syzkaller hit the following crash on
e40fd8d6b4d9f59b160faa1736f78fc07533ff37
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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


Buffer I/O error on dev loop0, logical block 10, lost async page write
INFO: task syz-executor1:20627 blocked for more than 120 seconds.
Not tainted 4.15.0-rc2-next-20171207+ #62
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1 D23352 20627 3384 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2800 [inline]
__schedule+0x8eb/0x2060 kernel/sched/core.c:3376
schedule+0xf5/0x430 kernel/sched/core.c:3435
io_schedule+0x1c/0x70 kernel/sched/core.c:5043
wait_on_page_bit_common mm/filemap.c:1099 [inline]
__lock_page+0x585/0x740 mm/filemap.c:1272
lock_page include/linux/pagemap.h:483 [inline]
write_cache_pages+0xb2b/0x14a0 mm/page-writeback.c:2206
generic_writepages+0xe9/0x150 mm/page-writeback.c:2325
blkdev_writepages+0x1d/0x30 fs/block_dev.c:1939
do_writepages+0xff/0x170 mm/page-writeback.c:2340
__filemap_fdatawrite_range+0x32f/0x460 mm/filemap.c:444
__filemap_fdatawrite mm/filemap.c:452 [inline]
filemap_fdatawrite mm/filemap.c:457 [inline]
filemap_write_and_wait+0x59/0xd0 mm/filemap.c:616
__sync_blockdev fs/block_dev.c:448 [inline]
sync_blockdev.part.27+0x50/0x70 fs/block_dev.c:457
sync_blockdev fs/block_dev.c:444 [inline]
set_blocksize+0x140/0x260 fs/block_dev.c:119
loop_set_fd drivers/block/loop.c:936 [inline]
lo_ioctl+0xcf1/0x1b90 drivers/block/loop.c:1358
__blkdev_driver_ioctl block/ioctl.c:303 [inline]
blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601
block_ioctl+0xea/0x130 fs/block_dev.c:1860
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: 0033:0x452a39
RSP: 002b:00007faa7bbaac58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000007580d8 RCX: 0000000000452a39
RDX: 0000000000000015 RSI: 0000000000004c00 RDI: 0000000000000014
RBP: 0000000000000179 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ef3f8
R13: 00000000ffffffff R14: 00007faa7bbab6d4 R15: 000000000000000e

Showing all locks held in the system:
3 locks held by kworker/u4:1/21:
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
__write_once_size include/linux/compiler.h:212 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
set_work_data kernel/workqueue.c:619 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<000000003e18825f>]
process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
#1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at:
[<000000009ee6c6b7>] process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
#2: (&type->s_umount_key#25){++++}, at: [<00000000935880a3>]
trylock_super+0x20/0x100 fs/super.c:395
2 locks held by khungtaskd/673:
#0: (rcu_read_lock){....}, at: [<000000002316dfa5>]
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: (rcu_read_lock){....}, at: [<000000002316dfa5>] watchdog+0x1c5/0xd60
kernel/hung_task.c:249
#1: (tasklist_lock){.+.+}, at: [<0000000088a78c0b>]
debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
1 lock held by rsyslogd/2998:
#0: (&f->f_pos_lock){+.+.}, at: [<000000002d6db5d9>] spin_lock
include/linux/spinlock.h:315 [inline]
#0: (&f->f_pos_lock){+.+.}, at: [<000000002d6db5d9>] double_lock_hb
kernel/futex.c:1498 [inline]
#0: (&f->f_pos_lock){+.+.}, at: [<000000002d6db5d9>] futex_wake_op
kernel/futex.c:1636 [inline]
#0: (&f->f_pos_lock){+.+.}, at: [<000000002d6db5d9>]
do_futex+0x138f/0x2280 kernel/futex.c:3483
2 locks held by getty/3120:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3121:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3122:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3123:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3124:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3125:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/16271:
#0: (&tty->ldisc_sem){++++}, at: [<0000000067ed2db8>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000502e5c39>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
1 lock held by syz-executor1/20627:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000557ff4c8>]
lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
1 lock held by syz-executor1/20636:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000557ff4c8>]
lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
1 lock held by syz-executor1/20643:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000557ff4c8>]
lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
1 lock held by blkid/20622:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000557ff4c8>]
lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
1 lock held by syz-executor2/20632:
#0: (&bdev->bd_mutex){+.+.}, at: [<00000000f0d4c738>]
iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145
1 lock held by syz-executor2/20656:
#0: (&bdev->bd_mutex){+.+.}, at: [<00000000f0d4c738>]
iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145

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

NMI backtrace for cpu 0
CPU: 0 PID: 673 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171207+ #62
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
nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x122/0x180 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:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0x90c/0xd60 kernel/hung_task.c:249
kthread+0x37a/0x440 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.
Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>

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Note: if the crash happens again, it will cause creation of a new bug
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[Dmitry Vyukov]

On Sun, Dec 10, 2017 at 2:33 PM, syzbot
<bot+476e4a33b7cd414ba5...@syzkaller.appspotmail.com>
wrote:

+loop maintainers

#syz dup: INFO: task hung in lo_ioctl

> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzk...@googlegroups.com.
> Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is merged into any tree, reply to this email with:
> #syz fix: exact-commit-title
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line in the email body.
>

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