INFO: task hung in ksys_sync_file_range

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
642e7fd23353e22290e3d51719fcb658dc252342 (Tue Apr 3 04:22:12 2018 +0000)
Merge branch 'syscalls-next' of
git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=34f334e7536fb1addcaa

So far this crash happened 2 times on upstream.
Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=5912521160523776
Kernel config:
https://syzkaller.appspot.com/x/.config?id=-6874493495260513980
compiler: gcc (GCC) 7.1.1 20170620
CC: [a...@linux.intel.com ak...@linux-foundation.org arya...@virtuozzo.com
ja...@suse.cz jla...@redhat.com linux-...@vger.kernel.org
linu...@kvack.org mgo...@techsingularity.net rgol...@suse.com
vi...@zeniv.linux.org.uk]

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Reported-by: syzbot+34f334...@syzkaller.appspotmail.com
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Buffer I/O error on dev loop0, logical block 64, async page read
INFO: task syz-executor2:26524 blocked for more than 120 seconds.
Not tainted 4.16.0+ #377
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2 D25560 26524 4540 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2848 [inline]
__schedule+0x8fb/0x1ef0 kernel/sched/core.c:3490
schedule+0xf5/0x430 kernel/sched/core.c:3549
io_schedule+0x1c/0x70 kernel/sched/core.c:5169
wait_on_page_bit_common+0x4b3/0x770 mm/filemap.c:1099
wait_on_page_bit mm/filemap.c:1132 [inline]
wait_on_page_writeback include/linux/pagemap.h:546 [inline]
__filemap_fdatawait_range+0x282/0x430 mm/filemap.c:533
file_fdatawait_range+0x47/0x60 mm/filemap.c:581
ksys_sync_file_range+0x19a/0x230 fs/sync.c:346
SYSC_sync_file_range fs/sync.c:370 [inline]
SyS_sync_file_range+0x2c/0x40 fs/sync.c:367
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4552d9
RSP: 002b:00007f3351f0ec68 EFLAGS: 00000246 ORIG_RAX: 0000000000000115
RAX: ffffffffffffffda RBX: 00007f3351f0f6d4 RCX: 00000000004552d9
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000064c R14: 00000000006fc7c0 R15: 0000000000000001

Showing all locks held in the system:
2 locks held by khungtaskd/879:
#0: 00000000fcb119d9 (rcu_read_lock){....}, at:
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: 00000000fcb119d9 (rcu_read_lock){....}, at: watchdog+0x1d6/0xd70
kernel/hung_task.c:249
#1: 000000005555c0f7 (tasklist_lock){.+.+}, at:
debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470
2 locks held by getty/4466:
#0: 0000000074d4b006 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000002f1de680 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4467:
#0: 000000009b107050 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000008b3c50c4 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4468:
#0: 000000006933b306 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000006afb7604 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4469:
#0: 00000000b20faea3 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000e1649d2a (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4470:
#0: 00000000022f154f (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000aba95184 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4471:
#0: 00000000132df053 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000033fb0e22 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
3 locks held by kworker/u4:6/6559:
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at:
__write_once_size include/linux/compiler.h:215 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at:
atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at: set_work_data
kernel/workqueue.c:619 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: 000000005cf0d5db ((wq_completion)"writeback"){+.+.}, at:
process_one_work+0xb83/0x1c40 kernel/workqueue.c:2084
#1: 00000000bfe7e976 ((work_completion)(&(&wb->dwork)->work)){+.+.}, at:
process_one_work+0xbd9/0x1c40 kernel/workqueue.c:2088
#2: 0000000038aee317 (&type->s_umount_key#35){++++}, at:
trylock_super+0x20/0x100 fs/super.c:395
2 locks held by getty/8099:
#0: 00000000836658af (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000005ad34c59 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131

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

NMI backtrace for cpu 1
CPU: 1 PID: 879 Comm: khungtaskd Not tainted 4.16.0+ #377
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+0x1a7/0x27d lib/dump_stack.c:53
nmi_cpu_backtrace+0x1e0/0x220 lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x123/0x180 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+0x969/0xd70 kernel/hung_task.c:249
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


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[syzbot]

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