[v6.6] INFO: task hung in migrate_pages_batch (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 924b4a879cbb Linux 6.6.142
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=169798ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=90249d2d52c08134
dashboard link: https://syzkaller.appspot.com/bug?extid=cbbed398b9fbc907084a
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bd13425862f1/disk-924b4a87.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/eaa5de9e440b/vmlinux-924b4a87.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5a9aa3293c15/bzImage-924b4a87.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cbbed3...@syzkaller.appspotmail.com

INFO: task syz.4.2538:14864 blocked for more than 145 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.2538 state:D stack:24400 pid:14864 ppid:6777 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
io_schedule+0x80/0xd0 kernel/sched/core.c:9023
folio_wait_bit_common+0x714/0xfa0 mm/filemap.c:1329
migrate_folio_unmap mm/migrate.c:1162 [inline]
migrate_pages_batch+0x1393/0x3440 mm/migrate.c:1672
migrate_pages_sync mm/migrate.c:1865 [inline]
migrate_pages+0x1f5a/0x27a0 mm/migrate.c:1947
compact_zone+0x2200/0x43a0 mm/compaction.c:2515
compact_node+0x195/0x300 mm/compaction.c:2807
compact_nodes mm/compaction.c:2820 [inline]
sysctl_compaction_handler+0xf9/0x1a0 mm/compaction.c:2866
proc_sys_call_handler+0x463/0x6d0 fs/proc/proc_sysctl.c:599
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x738/0xc30 fs/read_write.c:860
iter_file_splice_write+0x6a3/0xcb0 fs/splice.c:736
do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0xe8/0x130 fs/splice.c:1142
splice_direct_to_actor+0x304/0x8c0 fs/splice.c:1088
do_splice_direct+0x1d5/0x2f0 fs/splice.c:1194
do_sendfile+0x5f2/0xef0 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1316 [inline]
__se_sys_sendfile64+0xe0/0x1a0 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9c7259ce59
RSP: 002b:00007f9c73547028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f9c72815fa0 RCX: 00007f9c7259ce59
RDX: 00002000000000c0 RSI: 000000000000000c RDI: 000000000000000d
RBP: 00007f9c72632d6f R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000a R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9c72816038 R14: 00007f9c72815fa0 R15: 00007ffdff5d2cc8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by getty/5532:
#0: ffff8880318120a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000326e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x433/0x1390 drivers/tty/n_tty.c:2217
3 locks held by kworker/u5:0/12004:
#0: ffff88806c4ef138 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#0: ffff88806c4ef138 ((wq_completion)hci0){+.+.}-{0:0}, at: process_scheduled_works+0x96f/0x15d0 kernel/workqueue.c:2730
#1: ffffc900033e7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#1: ffffc900033e7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x96f/0x15d0 kernel/workqueue.c:2730
#2: ffff88806853ce70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x1d4/0x380 net/bluetooth/hci_sync.c:332
1 lock held by udevd/12453:
#0: ffff888021cf44c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:805
1 lock held by udevd/14104:
#0: ffff8881417f04c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:805
1 lock held by syz.4.2538/14864:
#0: ffff88806876a418 (sb_writers#3){.+.+}-{0:0}, at: do_sendfile+0x5cf/0xef0 fs/read_write.c:1253
2 locks held by syz.2.2802/15827:
1 lock held by syz.5.2809/15842:
#0: ffffffff8d137a00 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x580 kernel/rcu/tree.c:4089

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 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+0xf3d/0xf80 kernel/hung_task.c:379
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 88 1f 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 43 e4 3f 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffffff8ce07d80 EFLAGS: 000002c2
RAX: c3da1985de60cc00 RBX: ffffffff8162af3d RCX: c3da1985de60cc00
RDX: 0000000000000001 RSI: ffffffff8acacbe0 RDI: ffffffff8b1c9c20
RBP: ffffffff8ce07eb8 R08: ffff8880b8e36bab R09: 1ffff110171c6d75
R10: dffffc0000000000 R11: ffffed10171c6d76 R12: 1ffffffff19c0fbc
R13: dffffc0000000000 R14: 1ffffffff19d2688 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555e5ac4e8 CR3: 0000000058a5f000 CR4: 00000000003506f0
Call Trace:
<TASK>
arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
default_idle+0x13/0x20 arch/x86/kernel/process.c:753
default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
cpuidle_idle_call kernel/sched/idle.c:178 [inline]
do_idle+0x33d/0x590 kernel/sched/idle.c:302
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
rest_init+0x2e2/0x300 init/main.c:744
arch_call_rest_init+0xe/0x10 init/main.c:840
start_kernel+0x459/0x4e0 init/main.c:1085
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
secondary_startup_64_no_verify+0x179/0x17b
</TASK>


---
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