INFO: task hung in fat_write_inode

Status: auto-obsoleted due to no activity on 2023/12/17 10:07
Subsystems: exfat
[Documentation on labels]
First crash: 127d, last: 127d
Cause bisection: introduced by (bisect log) :
commit fb96458067a8043c256befe4bfe4fb3ebc81de1b
Author: Matthew Wilcox (Oracle) <>
Date: Mon Oct 16 20:10:48 2023 +0000

  buffer: return bool from grow_dev_folio()

Crash: INFO: task hung in fat_write_inode (log)
Repro: C syz .config
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] [exfat?] INFO: task hung in fat_write_inode 0 (2) 2023/11/03 12:27
[syzbot] Monthly exfat report (Oct 2023) 0 (1) 2023/10/25 13:11
Last patch testing requests (1)
Created Duration User Patch Repo Result
2023/11/01 18:56 24m retest repro linux-next OK log
Cause bisection attempts (3)
Created Duration User Patch Repo Result
2023/11/03 07:07 5h19m bisect linux-next job log (1) log
2023/10/27 00:57 4h17m bisect linux-next error job log (0)
2023/10/19 14:20 6h29m bisect linux-next error job log (0)

Sample crash report:
INFO: task kworker/u4:11:2872 blocked for more than 143 seconds.
      Not tainted 6.6.0-rc6-next-20231018-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:11   state:D stack:23520 pid:2872  tgid:2872  ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 context_switch kernel/sched/core.c:5369 [inline]
 __schedule+0xee4/0x5a10 kernel/sched/core.c:6680
 __schedule_loop kernel/sched/core.c:6757 [inline]
 schedule+0xe7/0x270 kernel/sched/core.c:6772
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6829
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x969/0x1340 kernel/locking/mutex.c:747
 fat_write_inode fs/fat/inode.c:918 [inline]
 fat_write_inode+0xfc/0x180 fs/fat/inode.c:911
 write_inode fs/fs-writeback.c:1456 [inline]
 __writeback_single_inode+0xa84/0xe60 fs/fs-writeback.c:1673
 writeback_sb_inodes+0x5a2/0x1090 fs/fs-writeback.c:1899
 __writeback_inodes_wb+0xff/0x2d0 fs/fs-writeback.c:1970
 wb_writeback+0x7fe/0xaa0 fs/fs-writeback.c:2077
 wb_check_background_flush fs/fs-writeback.c:2147 [inline]
 wb_do_writeback fs/fs-writeback.c:2235 [inline]
 wb_workfn+0x86a/0xfd0 fs/fs-writeback.c:2262
 process_one_work+0x8a2/0x15e0 kernel/workqueue.c:2630
 process_scheduled_works kernel/workqueue.c:2703 [inline]
 worker_thread+0x8b9/0x1290 kernel/workqueue.c:2784
 kthread+0x33c/0x440 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8cbacbe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
 #0: ffffffff8cbacbe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
 #0: ffffffff8cbacbe0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x75/0x340 kernel/locking/lockdep.c:6613
4 locks held by kworker/u4:11/2872:
 #0: ffff888142249d38 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x78a/0x15e0 kernel/workqueue.c:2605
 #1: ffffc9000aeffd80 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7f4/0x15e0 kernel/workqueue.c:2606
 #2: ffff888018e6c0e0 (&type->s_umount_key#45){++++}-{3:3}, at: super_trylock_shared+0x1e/0xf0 fs/super.c:610
 #3: ffff88807b4281d0 (&sbi->s_lock){+.+.}-{3:3}, at: fat_write_inode fs/fat/inode.c:918 [inline]
 #3: ffff88807b4281d0 (&sbi->s_lock){+.+.}-{3:3}, at: fat_write_inode+0xfc/0x180 fs/fat/inode.c:911
2 locks held by getty/4814:
 #0: ffff88814b6680a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900031332f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xfc6/0x1490 drivers/tty/n_tty.c:2201
4 locks held by syz-executor175/5063:


NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted 6.6.0-rc6-next-20231018-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x277/0x380 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x299/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf87/0x1210 kernel/hung_task.c:379
 kthread+0x33c/0x440 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5063 Comm: syz-executor175 Not tainted 6.6.0-rc6-next-20231018-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4788 [inline]
RIP: 0010:__lock_acquire+0x5b2/0x5dc0 kernel/locking/lockdep.c:5086
Code: b8 0a 00 00 41 89 ef 41 83 ef 01 0f 88 79 1f 00 00 49 b8 00 00 00 00 00 fc ff df 49 63 c7 48 8d 04 80 4c 8d a4 c7 e1 0a 00 00 <eb> 12 41 83 ef 01 49 83 ec 28 41 83 ff ff 0f 84 0c 0b 00 00 4d 8d
RSP: 0018:ffffc90003a6f3e0 EFLAGS: 00000002
RAX: 000000000000000a RBX: 0000000000000018 RCX: 0000000000000000
RDX: 1ffff1100f6868c7 RSI: 0000000000000001 RDI: ffff88807b433b80
RBP: 0000000000000003 R08: dffffc0000000000 R09: fffffbfff2344fc8
R10: ffffffff91a27e47 R11: 1ffffffff1976fb9 R12: ffff88807b4346b1
R13: ffff88807b4346b8 R14: ffffffff8cbacbe0 R15: 0000000000000002
FS:  00005555556c7380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055f81ca48600 CR3: 0000000077b86000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 lock_acquire kernel/locking/lockdep.c:5753 [inline]
 lock_acquire+0x1b2/0x530 kernel/locking/lockdep.c:5718
 rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
 rcu_read_lock include/linux/rcupdate.h:747 [inline]
 filemap_get_entry+0xdb/0x460 mm/filemap.c:1803
 __filemap_get_folio+0x56/0xa90 mm/filemap.c:1851
 __find_get_block_slow fs/buffer.c:203 [inline]
 __find_get_block fs/buffer.c:1406 [inline]
 __find_get_block+0x170/0xc30 fs/buffer.c:1400
 __getblk_slow+0x10c/0x6b0 fs/buffer.c:1134
 bdev_getblk+0xad/0xc0 fs/buffer.c:1434
 __getblk include/linux/buffer_head.h:358 [inline]
 sb_getblk include/linux/buffer_head.h:364 [inline]
 fat_mirror_bhs+0x244/0x5d0 fs/fat/fatent.c:388
 fat_alloc_clusters+0xcb2/0xf70 fs/fat/fatent.c:543
 fat_alloc_new_dir+0x107/0xc90 fs/fat/dir.c:1144
 vfat_mkdir+0x151/0x350 fs/fat/namei_vfat.c:859
 vfs_mkdir+0x577/0x820 fs/namei.c:4105
 do_mkdirat+0x2fd/0x3a0 fs/namei.c:4128
 __do_sys_mkdirat fs/namei.c:4143 [inline]
 __se_sys_mkdirat fs/namei.c:4141 [inline]
 __x64_sys_mkdirat+0x115/0x170 fs/namei.c:4141
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
RIP: 0033:0x7f1b0ce56b59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc6cb671e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f1b0ce56b59
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 00000000ffffff9c
RBP: 00007f1b0ceca5f0 R08: 000000000000024e R09: 00005555556c84c0
R10: 00007ffc6cb670b0 R11: 0000000000000246 R12: 00007ffc6cb67210
R13: 00007ffc6cb67438 R14: 431bde82d7b634db R15: 00007f1b0ce9f03b
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 2.510 msecs

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/10/18 10:06 linux-next 2dac75696c6d 342b9c55 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root INFO: task hung in fat_write_inode
2023/10/18 05:06 linux-next 2dac75696c6d 342b9c55 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in fat_write_inode
* Struck through repros no longer work on HEAD.