buffer_io_error: 20 callbacks suppressed Buffer I/O error on dev loop0, logical block 15, async page read kworker/dying (40) used greatest stack depth: 8328 bytes left INFO: task syz-executor1:20372 blocked for more than 120 seconds. Not tainted 4.16.0-rc7+ #374 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D23808 20372 4521 0x00000004 Call Trace: context_switch kernel/sched/core.c:2862 [inline] __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440 schedule+0xf5/0x430 kernel/sched/core.c:3499 io_schedule+0x1c/0x70 kernel/sched/core.c:5115 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 filemap_fdatawait_keep_errors+0x2a/0xb0 mm/filemap.c:600 fdatawait_one_bdev+0x50/0x70 fs/sync.c:95 iterate_bdevs+0x109/0x260 fs/block_dev.c:2162 sys_sync+0x120/0x1c0 fs/sync.c:117 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x454e79 RSP: 002b:00007feae5338c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2 RAX: ffffffffffffffda RBX: 00007feae53396d4 RCX: 0000000000454e79 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000064b R14: 00000000006fb7a8 R15: 0000000000000001 Showing all locks held in the system: 3 locks held by kworker/u4:1/21: #0: ((wq_completion)"writeback"){+.+.}, at: [<000000006cc63b5b>] work_static include/linux/workqueue.h:198 [inline] #0: ((wq_completion)"writeback"){+.+.}, at: [<000000006cc63b5b>] set_work_data kernel/workqueue.c:619 [inline] #0: ((wq_completion)"writeback"){+.+.}, at: [<000000006cc63b5b>] set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline] #0: ((wq_completion)"writeback"){+.+.}, at: [<000000006cc63b5b>] process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084 #1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: [<000000001b0813a2>] process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088 #2: (&type->s_umount_key#34){.+.+}, at: [<0000000079669791>] trylock_super+0x20/0x100 fs/super.c:395 2 locks held by khungtaskd/876: #0: (rcu_read_lock){....}, at: [<0000000041ee77c8>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<0000000041ee77c8>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000f5ffab60>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4444: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4445: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4446: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4447: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4448: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4449: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4450: #0: (&tty->ldisc_sem){++++}, at: [<00000000f31f39bf>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000f4378fd1>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 1 lock held by syz-executor1/20372: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000a01e827c>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2160 1 lock held by syz-executor1/20375: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000a01e827c>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2160 1 lock held by blkid/20359: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000e6081826>] blkdev_put+0x2a/0x4f0 fs/block_dev.c:1808 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 876 Comm: khungtaskd Not tainted 4.16.0-rc7+ #374 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+0x194/0x24d lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 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+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406 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