INFO: task syz-executor0:13396 blocked for more than 140 seconds.
      Not tainted 4.9.119-g9dc978d #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28360 13396   3872 0x00000004
 ffff8801d0090000 ffff8801d85d9a40 ffff8801d85d9a40 ffff8801cba69800
 ffff8801db221c18 ffff88019b3874a8 ffffffff839ebdcd dffffc0000000000
 ffff8801d63a4d70 ffff88019b387468 00ff8801d00908c0 ffff8801db2224e8
Call Trace:
 [<ffffffff839ed3cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff815c8102>] d_wait_lookup fs/dcache.c:2455 [inline]
 [<ffffffff815c8102>] d_alloc_parallel+0xeb2/0x17c0 fs/dcache.c:2537
 [<ffffffff815950bc>] lookup_slow+0x19c/0x470 fs/namei.c:1650
 [<ffffffff815a16e6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a3409>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a447d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e620>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff8156e620>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81426027>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3675:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d859c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157307e>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157307e>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fae72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821208d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/13396:
 #0:  (&sb->s_type->i_mutex_key#22){++++++}, at: [<ffffffff81595061>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#22){++++++}, at: [<ffffffff81595061>] lookup_slow+0x141/0x470 fs/namei.c:1645
2 locks held by syz-executor0/13398:
 #0:  (&sb->s_type->i_mutex_key#22){++++++}, at: [<ffffffff81595061>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#22){++++++}, at: [<ffffffff81595061>] lookup_slow+0x141/0x470 fs/namei.c:1645
 #1:  (&sbi->s_lock){+.+.+.}, at: [<ffffffff818da421>] vfat_lookup+0xd1/0x530 fs/fat/namei_vfat.c:729

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85f7d08 ffffffff81eb4be9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d85f7d40
 ffffffff81ebfee7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfee7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe7a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 13378 Comm: syz-executor0 Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cba69800 task.stack: ffff88019ba40000
RIP: 0010:[<ffffffff8135eaf0>] 
c [<ffffffff8135eaf0>] check_kcov_mode kernel/kcov.c:66 [inline]
RIP: 0010:[<ffffffff8135eaf0>] 
c [<ffffffff8135eaf0>] __sanitizer_cov_trace_pc+0x20/0x50 kernel/kcov.c:100
RSP: 0000:ffff88019ba46fa8  EFLAGS: 00000246
RAX: ffff8801cba69800 RBX: ffffea0006b685c0 RCX: ffffc900008c9000
RDX: 0000000000000000 RSI: ffffffff81f1c769 RDI: ffff8801cba6a0c4
RBP: ffff88019ba46fa8 R08: ffff8801cba6a138 R09: 0000000000000001
R10: ffff8801cba69800 R11: 1ffff1003974d422 R12: ffff8801cbcb7ce8
R13: dffffc0000000000 R14: 0000000002420848 R15: ffff8801d6196548
FS:  00007fcf608d3700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fadd5b8d000 CR3: 00000001c0786000 CR4: 00000000001606f0
Stack:
 ffff88019ba46fb8
c ffffffff81f1c769
c ffff88019ba46fd8
c ffffffff8127f645
c
 e856a6528b8646f7
c ffffea0006b685c0
c ffff88019ba46fe8
c ffffffff8127c227
c
 ffff88019ba47050
c ffffffff814391bb
c ffffffff81438e70
c ffffffff81624533
c
Call Trace:
 [<ffffffff81f1c769>] debug_smp_processor_id+0x9/0x20 lib/smp_processor_id.c:56
 [<ffffffff8127f645>] __rcu_is_watching kernel/rcu/tree.c:1053 [inline]
 [<ffffffff8127f645>] rcu_is_watching+0x15/0xa0 kernel/rcu/tree.c:1067
 [<ffffffff8127c227>] rcu_read_lock_held+0x87/0xc0 kernel/rcu/update.c:293
 [<ffffffff814391bb>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<ffffffff814391bb>] find_get_entry+0x34b/0x540 mm/filemap.c:1095
 [<ffffffff8143a2eb>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1201
 [<ffffffff81625809>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff81625809>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff81625809>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff81625809>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff81625809>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff816290ed>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818b78e8>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818b78e8>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818bf6e7>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818bf6e7>] fat_search_long+0x277/0x1180 fs/fat/dir.c:477
 [<ffffffff818d9c54>] vfat_find+0x134/0x180 fs/fat/namei_vfat.c:708
 [<ffffffff818da431>] vfat_lookup+0xe1/0x530 fs/fat/namei_vfat.c:731
 [<ffffffff8159515e>] lookup_slow+0x23e/0x470 fs/namei.c:1668
 [<ffffffff815a16e6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a3409>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a447d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e5dd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156e5dd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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