INFO: task hung in wb_writeback

Status: upstream: reported syz repro on 2026/08/23 05:26
Reported-by: syzbot+a822ffb310c1edefbac1@syzkaller.appspotmail.com
First crash: 26d, last: 26d

Sample crash report:
INFO: task kworker/u4:0:11 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 wb_writeback+0x472/0xbe0 fs/fs-writeback.c:2158
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 </TASK>
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:4    state:D stack:23560 pid:61    ppid:2      flags:0x00004000
 (flush-7:2)


Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 wb_writeback+0x472/0xbe0 fs/fs-writeback.c:2158
 wb_check_background_flush fs/fs-writeback.c:2228 [inline]
 wb_do_writeback fs/fs-writeback.c:2316 [inline]
 wb_workfn+0xb8e/0xe60 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 kthread+0x2fa/0x390 kernel/kthread.c:388
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 hfsplus_find_init+0x154/0x1d0 fs/hfsplus/bfind.c:28
 hfsplus_cat_write_inode+0x214/0x860 fs/hfsplus/inode.c:618
 writeback_sb_inodes+0x813/0x1020 fs/fs-writeback.c:1977
 __writeback_inodes_wb+0x114/0x240 fs/fs-writeback.c:2048
 wb_writeback+0x472/0xbe0 fs/fs-writeback.c:2158

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/23 05:25 linux-6.6.y c610b395b0a5 1e72964b .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-6-kasan INFO: task hung in wb_writeback
* Struck through repros no longer work on HEAD.