INFO: task hung in __writeback_inodes_sb_nr

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
69bfd470f4623d2d57ad62cb33791cded0c662f4 (Thu Apr 26 04:23:38 2018 +0000)
Merge tag 'for_v4.17-rc3' of
git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=c67f5f31321f9fd5885e

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=6105736908111872
Kernel config:
https://syzkaller.appspot.com/x/.config?id=7043958930931867332
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c67f5f...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
INFO: task syz-executor6:4586 blocked for more than 120 seconds.
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
Not tainted 4.17.0-rc2+ #18
b_state=0x00000029, b_size=512
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6 D
device loop6 blocksize: 4096
21224 4586 1 0x00000004
Call Trace:
__find_get_block_slow() failed. block=1, b_blocknr=8
context_switch kernel/sched/core.c:2848 [inline]
__schedule+0x801/0x1e30 kernel/sched/core.c:3490
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
schedule+0xef/0x430 kernel/sched/core.c:3549
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
wb_wait_for_completion+0x1ed/0x2d0 fs/fs-writeback.c:221
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__writeback_inodes_sb_nr+0x3e8/0x550 fs/fs-writeback.c:2340
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
writeback_inodes_sb_nr fs/fs-writeback.c:2357 [inline]
writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2372
__sync_filesystem fs/sync.c:36 [inline]
sync_filesystem+0x15f/0x310 fs/sync.c:64
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
generic_shutdown_super+0xd7/0x520 fs/super.c:429
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
kill_block_super+0xa4/0x100 fs/super.c:1191
b_state=0x00000029, b_size=512
deactivate_locked_super+0x97/0x100 fs/super.c:316
device loop6 blocksize: 4096
deactivate_super+0x188/0x1b0 fs/super.c:347
__find_get_block_slow() failed. block=1, b_blocknr=8
cleanup_mnt+0xbf/0x160 fs/namespace.c:1174
__cleanup_mnt+0x16/0x20 fs/namespace.c:1181
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
task_work_run+0x1e4/0x290 kernel/task_work.c:113
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x2bd/0x310 arch/x86/entry/common.c:166
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
entry_SYSCALL_64_after_hwframe+0x49/0xbe
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
RIP: 0033:0x457d97
RSP: 002b:00007ffebca6fff8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000457d97
__find_get_block_slow() failed. block=1, b_blocknr=8
RDX: 0000000001a41a13 RSI: 0000000000000002 RDI: 00007ffebca71160
RBP: 00007ffebca71160 R08: 0000000000000000 R09: 000000000000000b
R10: 0000000000000005 R11: 0000000000000246 R12: 0000000001a41940
R13: 0000000000000000 R14: 000000000000033e R15: 000000000002f882
b_state=0x00000029, b_size=512

Showing all locks held in the system:
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
2 locks held by khungtaskd/892:
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
#0: (ptrval) (rcu_read_lock){....}
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249
#1:
__find_get_block_slow() failed. block=1, b_blocknr=8
(ptrval) (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a
kernel/locking/lockdep.c:4470
1 lock held by rsyslogd/4415:
b_state=0x00000029, b_size=512
#0: (ptrval) (&f->f_pos_lock
device loop6 blocksize: 4096
){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766
__find_get_block_slow() failed. block=1, b_blocknr=8
2 locks held by getty/4505:
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
#0: (ptrval)
__find_get_block_slow() failed. block=1, b_blocknr=8
(&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40
drivers/tty/tty_ldsem.c:365
#1:
b_state=0x00000029, b_size=512
(ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4506:
device loop6 blocksize: 4096
#0: (ptrval)
__find_get_block_slow() failed. block=1, b_blocknr=8
(&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40
drivers/tty/tty_ldsem.c:365
#1:
b_state=0x00000029, b_size=512
(ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4507:
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
#1: (ptrval)
b_state=0x00000029, b_size=512
device loop6 blocksize: 4096
(&ldata->atomic_read_lock){+.+.}
__find_get_block_slow() failed. block=1, b_blocknr=8
, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4508:
b_state=0x00000029, b_size=512
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
device loop6 blocksize: 4096
#1: (ptrval) (
__find_get_block_slow() failed. block=1, b_blocknr=8
&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0
drivers/tty/n_tty.c:2131
2 locks held by getty/4509:
b_state=0x00000029, b_size=512
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
device loop6 blocksize: 4096
#1: (ptrval)
__find_get_block_slow() failed. block=1, b_blocknr=8
(&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0
drivers/tty/n_tty.c:2131
2 locks held by getty/4510:
b_state=0x00000029, b_size=512
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1:
device loop6 blocksize: 4096
(ptrval) (&ldata->atomic_read_lock
__find_get_block_slow() failed. block=1, b_blocknr=8
){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4511:
b_state=0x00000029, b_size=512
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1:
device loop6 blocksize: 4096
(ptrval) (&ldata->atomic_read_lock
__find_get_block_slow() failed. block=1, b_blocknr=8
){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
1 lock held by syz-executor6/4586:
b_state=0x00000029, b_size=512
#0: (ptrval) (&type->s_umount_key#46){++++}, at:
deactivate_super+0x180/0x1b0 fs/super.c:346

device loop6 blocksize: 4096
=============================================

NMI backtrace for cpu 1
__find_get_block_slow() failed. block=1, b_blocknr=8
CPU: 1 PID: 892 Comm: khungtaskd Not tainted 4.17.0-rc2+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
b_state=0x00000029, b_size=512
nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
device loop6 blocksize: 4096
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+0xc10/0xf60 kernel/hung_task.c:249
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
kthread+0x345/0x410 kernel/kthread.c:238
device loop6 blocksize: 4096
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
__find_get_block_slow() failed. block=1, b_blocknr=8
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6 Comm: kworker/u4:0 Not tainted 4.17.0-rc2+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: writeback wb_workfn (flush-7:6)
RIP: 0010:print_time kernel/printk/printk.c:1221 [inline]
RIP: 0010:print_prefix+0x38e/0x3f0 kernel/printk/printk.c:1246
RSP: 0018:ffff8801d9a95ef0 EFLAGS: 00000086
RAX: 000000000000000f RBX: 0000000000000001 RCX: ffffffff876ba8ac
RDX: 0000000000000000 RSI: ffffffff876ba902 RDI: 0000000000000007
RBP: ffff8801d9a95f18 R08: ffff8801d9a88180 R09: fffffbfff11b09ec
R10: fffffbfff11b09ec R11: ffffffff88d84f63 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000172 R15: 000000002b166d01
FS: 0000000000000000(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000001cacec000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
msg_print_text+0x85/0x1c0 kernel/printk/printk.c:1269
console_unlock+0x4f5/0x1100 kernel/printk/printk.c:2369
vprintk_emit+0x6ad/0xdd0 kernel/printk/printk.c:1907
vprintk_default+0x28/0x30 kernel/printk/printk.c:1947
vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:379
printk+0x9e/0xba kernel/printk/printk.c:1980
__find_get_block_slow fs/buffer.c:231 [inline]
__find_get_block.cold.58+0x3a/0x103 fs/buffer.c:1287
__getblk_slow fs/buffer.c:1032 [inline]
__getblk_gfp+0x2a1/0xaf0 fs/buffer.c:1313
__bread_gfp+0x2d/0x310 fs/buffer.c:1347
sb_bread include/linux/buffer_head.h:309 [inline]
__fat_write_inode+0x33f/0xb40 fs/fat/inode.c:845
fat_write_inode+0x97/0x180 fs/fat/inode.c:894
write_inode fs/fs-writeback.c:1183 [inline]
__writeback_single_inode+0xf18/0x15c0 fs/fs-writeback.c:1382
writeback_sb_inodes+0x6f0/0x11a0 fs/fs-writeback.c:1587
wb_writeback+0x463/0xf50 fs/fs-writeback.c:1763
wb_do_writeback fs/fs-writeback.c:1908 [inline]
wb_workfn+0x46f/0x1770 fs/fs-writeback.c:1949
process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
kthread+0x345/0x410 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Code: 9b a0 2f b8 44 00 4c 89 f8 48 f7 e2 48 c1 ea 0b 49 89 d6 e8 a5 ea 18
00 4c 89 f1 31 f6 31 ff 48 c7 c2 e0 5a cb 87 e8 02 7d 0b 06 <48> 98 49 01
c4 e9 d7 fe ff ff 45 31 e4 e9 cf fe ff ff 45 31 e4


---
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