[syzbot] [block?] INFO: task hung in __rq_qos_throttle (2)

Hello,

syzbot found the following issue on:

HEAD commit:    0d8395707651 Merge tag 'soc-fixes-7.2-2' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1440fcc6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3e8a402093abe6b2
dashboard link: https://syzkaller.appspot.com/bug?extid=53706c567afab5131044
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=146d57b9580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14d54fb9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1f43b22650b3/disk-0d839570.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2a5a74ede35c/vmlinux-0d839570.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f66d75fb8a35/bzImage-0d839570.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

INFO: task kworker/u8:6:763 blocked in I/O wait for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:6    state:D stack:20032 pid:763   tgid:763   ppid:2      task_flags:0x4248060 flags:0x00080000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 io_schedule+0x7f/0xd0 kernel/sched/core.c:8154
 rq_qos_wait+0x266/0x360 block/blk-rq-qos.c:307
 __wbt_wait block/blk-wbt.c:598 [inline]
 wbt_wait+0x326/0x550 block/blk-wbt.c:658
 __rq_qos_throttle+0x6b/0xb0 block/blk-rq-qos.c:66
 rq_qos_throttle block/blk-rq-qos.h:164 [inline]
 blk_mq_get_new_requests block/blk-mq.c:3032 [inline]
 blk_mq_submit_bio+0x1522/0x2a40 block/blk-mq.c:3170
 __submit_bio_noacct_mq block/blk-core.c:756 [inline]
 submit_bio_noacct_nocheck+0x34e/0xa40 block/blk-core.c:790
 blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
 ext4_io_submit+0x11b/0x190 fs/ext4/page-io.c:404
 ext4_do_writepages+0x1293/0x47a0 fs/ext4/inode.c:2969
 ext4_writepages+0x241/0x3b0 fs/ext4/inode.c:3043
 do_writepages+0x338/0x560 mm/page-writeback.c:2571
 __writeback_single_inode+0x12e/0xf90 fs/fs-writeback.c:1787
 writeback_sb_inodes+0x9de/0x1b00 fs/fs-writeback.c:2079
 __writeback_inodes_wb+0x114/0x240 fs/fs-writeback.c:2155
 wb_writeback+0x42f/0xad0 fs/fs-writeback.c:2266
 wb_check_old_data_flush fs/fs-writeback.c:2370 [inline]
 wb_do_writeback fs/fs-writeback.c:2449 [inline]
 wb_workfn+0xc92/0x10f0 fs/fs-writeback.c:2477
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
INFO: task jbd2/sda1-8:4934 blocked in I/O wait for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:jbd2/sda1-8     state:D stack:25288 pid:4934  tgid:4934  ppid:2      task_flags:0x240040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 io_schedule+0x7f/0xd0 kernel/sched/core.c:8154
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:250
 __wait_on_bit+0xac/0x300 kernel/sched/wait_bit.c:52
 out_of_line_wait_on_bit+0x13b/0x190 kernel/sched/wait_bit.c:67
 wait_on_buffer include/linux/buffer_head.h:422 [inline]
 jbd2_journal_commit_transaction+0x2f1d/0x5b70 fs/jbd2/commit.c:834
 kjournald2+0x3bc/0x750 fs/jbd2/journal.c:199
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
INFO: task syz.0.252:6057 blocked in I/O wait for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.252       state:D stack:28200 pid:6057  tgid:6057  ppid:5759   task_flags:0x440040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 io_schedule+0x7f/0xd0 kernel/sched/core.c:8154
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:250
 __wait_on_bit+0xac/0x300 kernel/sched/wait_bit.c:52
 out_of_line_wait_on_bit+0x13b/0x190 kernel/sched/wait_bit.c:67
 wait_on_bit_io include/linux/wait_bit.h:105 [inline]
 do_get_write_access+0x661/0x1080 fs/jbd2/transaction.c:1113
 jbd2_journal_get_write_access+0x1d6/0x230 fs/jbd2/transaction.c:1263
 __ext4_journal_get_write_access+0x1c3/0x590 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x294/0x360 fs/ext4/inode.c:6427
 __ext4_mark_inode_dirty+0x13e/0x700 fs/ext4/inode.c:6602
 ext4_dirty_inode+0xd0/0x110 fs/ext4/inode.c:6639
 __mark_inode_dirty+0x3a8/0x13b0 fs/fs-writeback.c:2709
 generic_update_time fs/inode.c:2257 [inline]
 file_update_time_flags+0x3ee/0x4a0 fs/inode.c:2487
 ext4_page_mkwrite+0x224/0x1140 fs/ext4/inode.c:6805
 do_page_mkwrite+0x147/0x310 mm/memory.c:3684
 do_shared_fault mm/memory.c:5936 [inline]
 do_fault mm/memory.c:5998 [inline]
 do_pte_missing+0x757/0x34b0 mm/memory.c:4566
 handle_pte_fault mm/memory.c:6379 [inline]
 __handle_mm_fault mm/memory.c:6517 [inline]
 handle_mm_fault+0x1b36/0x3080 mm/memory.c:6686
 do_user_addr_fault+0xa4d/0x1340 arch/x86/mm/fault.c:1343
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7f83ac26ba23
RSP: 002b:00007fff430be250 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b34a24000 RSI: 0000000000040000 RDI: 00007f83ac5e0708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007fff430be4e0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/32:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
4 locks held by kworker/u8:6/763:
 #0: ffff88801c2ab940 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88801c2ab940 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc9000451fc40 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc9000451fc40 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffff88803604a0d8 (&type->s_umount_key#32){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:566
 #3: ffff888036048c18 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
 #3: ffff888036048c18 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1876 [inline]
 #3: ffff888036048c18 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x205/0x3b0 fs/ext4/inode.c:3042
2 locks held by getty/5359:
 #0: ffff8880361ec0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
3 locks held by syz.0.252/6057:
 #0: ffff888033cfd588 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:310
 #1: ffff88803604a548 (sb_pagefaults){.+.+}-{0:0}, at: percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 #1: ffff88803604a548 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs/super.h:19 [inline]
 #1: ffff88803604a548 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs/super.h:159 [inline]
 #1: ffff88803604a548 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x202/0x1140 fs/ext4/inode.c:6804
 #2: ffff888033db6938 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1fc3/0x2210 fs/jbd2/transaction.c:444
3 locks held by syz-executor/6064:
 #0: ffff88803604a450 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494
 #1: ffff8880764c1640 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #1: ffff8880764c1640 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #1: ffff8880764c1640 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #1: ffff8880764c1640 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:4955
 #2: ffff888033db6938 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1fc3/0x2210 fs/jbd2/transaction.c:444

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 32 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122
 nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 6c 80 02 e9 fe 5f 41 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d d3 8e 1a 00 fb f4 <e9> d7 5f 41 f5 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffc90000197e40 EFLAGS: 00000242
RAX: 00000000000e1b9b RBX: ffffffff819b4450 RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e226a0e RDI: ffffffff8c4bb880
RBP: ffffc90000197f10 R08: ffff8880b87338db R09: 1ffff110170e671b
R10: dffffc0000000000 R11: ffffed10170e671c R12: 0000000000000000
R13: 1ffff11003bd5000 R14: 1ffff92000032fd0 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88812505e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561c741e9660 CR3: 000000000e946000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/kernel/process.c:767 [inline]
 default_idle+0x9/0x20 arch/x86/kernel/process.c:768
 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x2e0/0x540 kernel/sched/idle.c:355
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x157
 </TASK>


---
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