[v6.1] INFO: task hung in exfat_write_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1321ab403b38 Linux 6.1.45
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1446c569a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=5afeea223ff7d6fa
dashboard link: https://syzkaller.appspot.com/bug?extid=25f77c2f928dab8c57a1
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/df0f614deffc/disk-1321ab40.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/df0f1be30831/vmlinux-1321ab40.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9e190f335ac9/bzImage-1321ab40.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+25f77c...@syzkaller.appspotmail.com

INFO: task kworker/u4:29:13738 blocked for more than 143 seconds.
Not tainted 6.1.45-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:29 state:D stack:23768 pid:13738 ppid:2 flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:3)
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5241 [inline]
__schedule+0x132c/0x4330 kernel/sched/core.c:6554
schedule+0xbf/0x180 kernel/sched/core.c:6630
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6689
__mutex_lock_common+0xe2b/0x2520 kernel/locking/mutex.c:679
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
exfat_write_inode+0x65/0x110 fs/exfat/inode.c:94
write_inode fs/fs-writeback.c:1443 [inline]
__writeback_single_inode+0x67d/0x11e0 fs/fs-writeback.c:1655
writeback_sb_inodes+0xc21/0x1ac0 fs/fs-writeback.c:1881
__writeback_inodes_wb+0x114/0x400 fs/fs-writeback.c:1952
wb_writeback+0x4b1/0xe10 fs/fs-writeback.c:2057
wb_check_background_flush fs/fs-writeback.c:2123 [inline]
wb_do_writeback fs/fs-writeback.c:2211 [inline]
wb_workfn+0xc9e/0x1020 fs/fs-writeback.c:2238
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2292
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2439
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8d12a0b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xd20 kernel/rcu/tasks.h:516
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8d12a8b0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xd20 kernel/rcu/tasks.h:516
1 lock held by khungtaskd/28:
#0: ffffffff8d129ee0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3270:
#0: ffff88814bde3098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc900031262f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a7/0x1db0 drivers/tty/n_tty.c:2188
4 locks held by kworker/u4:29/13738:
#0: ffff8881426bd938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x77a/0x11f0
#1: ffffc9000339fd20 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2267
#2: ffff888013b940e0 (&type->s_umount_key#49){++++}-{3:3}, at: trylock_super+0x1b/0xf0 fs/super.c:415
#3: ffff888013b900e0 (&sbi->s_lock){+.+.}-{3:3}, at: exfat_write_inode+0x65/0x110 fs/exfat/inode.c:94
5 locks held by syz-executor.3/28412:

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted 6.1.45-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
nmi_cpu_backtrace+0x4e1/0x560 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b0/0x3f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xf18/0xf60 kernel/hung_task.c:377
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 28412 Comm: syz-executor.3 Not tainted 6.1.45-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
RIP: 0010:__exfat_free_cluster+0x315/0x990 fs/exfat/fatent.c:184
Code: 44 8b 64 24 38 44 89 e6 e8 e8 86 30 ff 45 39 e5 48 89 5c 24 10 73 50 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 68 0f b6 04 01 <84> c0 0f 85 87 01 00 00 4d 89 fc 45 8d 74 1f fe 41 c1 ee 03 48 8b
RSP: 0018:ffffc9000a7df440 EFLAGS: 00000217
RAX: 0000000000000000 RBX: 000000004a904ab0 RCX: 1ffff11002772802
RDX: ffff88807bcb9dc0 RSI: 00000000e9100008 RDI: 000000004a904ab7
RBP: ffffc9000a7df558 R08: ffffffff82597878 R09: ffffed10129608e9
R10: 0000000000000000 R11: dffffc0000000001 R12: 00000000e9100008
R13: 000000004a904ab7 R14: 000000000004a904 R15: 0000000000000008
FS: 00007f91a68a46c0(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fefbdd77978 CR3: 0000000078230000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
exfat_free_cluster+0x73/0xc0 fs/exfat/fatent.c:232
__exfat_truncate+0x6ae/0x9d0 fs/exfat/file.c:186
exfat_truncate+0xf4/0x340 fs/exfat/file.c:210
exfat_setattr+0xad3/0xe10 fs/exfat/file.c:312
notify_change+0xdcd/0x1080 fs/attr.c:482
do_truncate+0x21c/0x300 fs/open.c:65
handle_truncate fs/namei.c:3216 [inline]
do_open fs/namei.c:3561 [inline]
path_openat+0x27e2/0x2e60 fs/namei.c:3714
do_filp_open+0x230/0x480 fs/namei.c:3741
do_sys_openat2+0x13b/0x500 fs/open.c:1318
do_sys_open fs/open.c:1334 [inline]
__do_sys_openat fs/open.c:1350 [inline]
__se_sys_openat fs/open.c:1345 [inline]
__x64_sys_openat+0x243/0x290 fs/open.c:1345
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f91a5a7cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f91a68a40c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f91a5b9c050 RCX: 00007f91a5a7cae9
RDX: 000000000000275a RSI: 0000000020000080 RDI: ffffffffffffff9c
RBP: 00007f91a5ac847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f91a5b9c050 R15: 00007ffd0bdd6578
</TASK>


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[syzbot]

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