__find_get_block_slow() failed. block=2, b_blocknr=8
b_state=0x00000029, b_size=512
device loop0 blocksize: 2048
__find_get_block_slow() failed. block=2, b_blocknr=8
b_state=0x00000029, b_size=512
INFO: task syz-executor0:6885 blocked for more than 140 seconds.
      Not tainted 4.9.124-g09eb2ba #31
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28520  6885   3731 0x00000004
 ffff8801d947e000 0000000000000000 ffff8801c2fc4a80 ffffffff84629800
 ffff8801db221c18 ffff880196b07808 ffffffff839f0afd ffffffff81237da7
 0000000000000000 ffff8801d947e8c0 0000000600000007 ffff8801db2224e8
Call Trace:
 [<ffffffff839f20ff>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fd738>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839fd738>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81eed907>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839fb50c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839fb50c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff815a9585>] inode_lock include/linux/fs.h:766 [inline]
 [<ffffffff815a9585>] do_last fs/namei.c:3312 [inline]
 [<ffffffff815a9585>] path_openat+0xed5/0x3590 fs/namei.c:3534
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff815729bd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff815729bd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] 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: [<ffffffff813689dc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81428248>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3538:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815dc7ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3635:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffba2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82125402>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/6885:
 #0:  (&sb->s_type->i_mutex_key#18){++++++}, at: [<ffffffff815a9585>] inode_lock include/linux/fs.h:766 [inline]
 #0:  (&sb->s_type->i_mutex_key#18){++++++}, at: [<ffffffff815a9585>] do_last fs/namei.c:3312 [inline]
 #0:  (&sb->s_type->i_mutex_key#18){++++++}, at: [<ffffffff815a9585>] path_openat+0xed5/0x3590 fs/namei.c:3534

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85cfd08 ffffffff81eb95e9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d85cfd40
 ffffffff81ec4927 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec4927>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec48ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81368f74>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368f74>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368f74>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368f74>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01b9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6809 Comm: syz-executor0 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff880196ce8000 task.stack: ffff880196cb8000
RIP: 0010:[<ffffffff821561db>] 
c [<ffffffff821561db>] inb arch/x86/include/asm/io.h:316 [inline]
RIP: 0010:[<ffffffff821561db>] 
c [<ffffffff821561db>] io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:413
RSP: 0018:ffff880196cbef40  EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: ffffffff82156181 RDI: ffffffff864ace78
RBP: ffff880196cbef50 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff864ace40
R13: 0000000000000020 R14: fffffbfff0c95a0f R15: fffffbfff0c959d1
FS:  00007f4ab7084700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000aba000 CR3: 00000001c3128000 CR4: 00000000001606f0
Stack:
 ffffffff864ace40
c 000000000000270b
c ffff880196cbefa0
c ffffffff82157da4
c
 ffffffff81ee4918
c ffffffff864ace88
c ffffffff864ad07a
c ffffffff864ace40
c
 000000000000003d
c ffffffff82157ef0
c dffffc0000000000
c 000000000000003d
c
Call Trace:
 [<ffffffff82157da4>] serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 [<ffffffff82157da4>] wait_for_xmitr+0x94/0x1e0 drivers/tty/serial/8250/8250_port.c:1997
 [<ffffffff82157f0f>] serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3103
 [<ffffffff82140739>] uart_console_write+0x59/0xf0 drivers/tty/serial/serial_core.c:1859
 [<ffffffff82164128>] serial8250_console_write+0x528/0x820 drivers/tty/serial/8250/8250_port.c:3169
 [<ffffffff82150c8f>] univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:594
 [<ffffffff8125decd>] call_console_drivers.isra.18.constprop.28+0x1ad/0x360 kernel/printk/printk.c:1589
 [<ffffffff81260ccf>] console_unlock+0x42f/0xb40 kernel/printk/printk.c:2449
 [<ffffffff81261828>] vprintk_emit+0x448/0x790 kernel/printk/printk.c:1903
 [<ffffffff81261b98>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
 [<ffffffff81261bbd>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
 [<ffffffff8142f016>] vprintk_func kernel/printk/internal.h:36 [inline]
 [<ffffffff8142f016>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
 [<ffffffff81cbf9d5>] __find_get_block_slow.cold.57+0x82/0xf0 fs/buffer.c:242
 [<ffffffff81628cde>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81629ae9>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81629ae9>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff8162d48d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818bc678>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818bc678>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818bf301>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818bf301>] fat_get_short_entry+0x131/0x2a0 fs/fat/dir.c:876
 [<ffffffff818bf85d>] fat_scan+0xfd/0x340 fs/fat/dir.c:961
 [<ffffffff818e6f49>] msdos_find+0xf9/0x2d0 fs/fat/namei_msdos.c:128
 [<ffffffff818e7865>] msdos_lookup+0x135/0x250 fs/fat/namei_msdos.c:208
 [<ffffffff8159f93d>] lookup_open+0x63d/0x1930 fs/namei.c:3203
 [<ffffffff815a9eb3>] do_last fs/namei.c:3315 [inline]
 [<ffffffff815a9eb3>] path_openat+0x1803/0x3590 fs/namei.c:3534
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff815729bd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff815729bd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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