syzbot

INFO: task kworker/u4:1:11 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:1    state:D stack:25616 pid:11    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 rwsem_down_write_slowpath+0xc2e/0x1110 kernel/locking/rwsem.c:1189
 f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
 f2fs_write_inode+0x531/0x760 fs/f2fs/inode.c:742
 write_inode fs/fs-writeback.c:1470 [inline]
 __writeback_single_inode+0x75b/0x1160 fs/fs-writeback.c:1687
 writeback_sb_inodes+0xb30/0x1850 fs/fs-writeback.c:1913
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:1984
 wb_writeback+0x494/0xd50 fs/fs-writeback.c:2089
 wb_check_background_flush fs/fs-writeback.c:2155 [inline]
 wb_do_writeback fs/fs-writeback.c:2243 [inline]
 wb_workfn+0xc1c/0xee0 fs/fs-writeback.c:2270
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Showing all locks held in the system:
2 locks held by kworker/u4:0/9:
4 locks held by kworker/u4:1/11:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000107d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff8880797420e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88807f741240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff88807f741240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2df70 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8cb2e790 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_preempt/16:
 #0: ffff8880b8e3ab18 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:538
1 lock held by khungtaskd/28:
 #0: ffffffff8cb2d5e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2d5e0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2d5e0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
4 locks held by kworker/u4:2/38:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000af7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88805c42e0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888025259240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff888025259240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
4 locks held by kworker/u4:3/46:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000b77d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff8880797120e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88805b9a1240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff88805b9a1240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
4 locks held by kworker/u4:4/57:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90001587d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff8880791e20e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff8880734e9240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff8880734e9240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
4 locks held by kworker/u4:5/2898:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc9000c537d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff888024f8e0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888027109240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff888027109240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
2 locks held by getty/4027:
 #0: ffff88814cfd6098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x429/0x1390 drivers/tty/n_tty.c:2198
5 locks held by syz.0.17/4434:
4 locks held by syz.1.18/4460:
5 locks held by syz.2.19/4480:
4 locks held by syz.3.20/4502:
4 locks held by kworker/u4:8/4509:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003b27d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88802872c0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888020a51240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff888020a51240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
6 locks held by syz.4.21/4539:
4 locks held by kworker/u4:10/4555:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003cb7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88807df1c0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888054ad5240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff888054ad5240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
4 locks held by syz.5.22/4573:
4 locks held by syz.6.23/4598:
4 locks held by kworker/u4:13/4631:
 #0: ffff88801b6ea138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90004067d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88807a7da0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88804e5cd240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2181 [inline]
 #3: ffff88804e5cd240 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4d5/0x6b0 fs/f2fs/segment.c:428
6 locks held by syz.7.24/4633:

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1d4/0x450 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+0xeee/0xf30 kernel/hung_task.c:377
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4598 Comm: syz.6.23 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:arch_irqs_disabled_flags arch/x86/include/asm/irqflags.h:125 [inline]
RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:132 [inline]
RIP: 0010:lock_is_held_type+0x11e/0x190 kernel/locking/lockdep.c:5707
Code: 48 c7 c7 a0 22 8c 8a e8 60 12 00 00 b8 ff ff ff ff 65 0f c1 05 83 80 d4 75 83 f8 01 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 <f7> 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b
RSP: 0018:ffffc90003ef6d18 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff88802a790000 RCX: df0c662112b38c00
RDX: 0000000000000000 RSI: ffffffff8a8c22a0 RDI: ffffffff8adf13a0
RBP: 0000000000000000 R08: ffffffff8c814703 R09: 1ffffffff19028e0
R10: dffffc0000000000 R11: fffffbfff19028e1 R12: 0000000000000004
R13: 0000000000000246 R14: ffffffff8cb2d640 R15: ffff88802a790b80
FS:  00007efd112e26c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561912288a38 CR3: 0000000027c00000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_is_held include/linux/lockdep.h:283 [inline]
 __might_resched+0x9b/0x630 kernel/sched/core.c:9931
 wait_on_inode include/linux/writeback.h:201 [inline]
 iget_locked+0xf9/0x830 fs/inode.c:1365
 f2fs_iget+0x52/0x4b30 fs/f2fs/inode.c:489
 gc_data_segment fs/f2fs/gc.c:1570 [inline]
 do_garbage_collect+0x2240/0x6210 fs/f2fs/gc.c:1776
 f2fs_gc+0xe58/0x2750 fs/f2fs/gc.c:1875
 f2fs_balance_fs+0x4e0/0x6b0 fs/f2fs/segment.c:429
 f2fs_map_blocks+0x1af6/0x3480 fs/f2fs/data.c:1729
 f2fs_preallocate_blocks fs/f2fs/file.c:4691 [inline]
 f2fs_file_write_iter+0xfec/0x2200 fs/f2fs/file.c:4893
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4b1/0xa30 fs/read_write.c:584
 ksys_write+0x14c/0x250 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7efd1039c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007efd112e2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007efd10615fa0 RCX: 00007efd1039c819
RDX: 0000000000ffe000 RSI: 0000200000000000 RDI: 0000000000000006
RBP: 00007efd10432c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efd10616038 R14: 00007efd10615fa0 R15: 00007ffdb84000b8
 </TASK>