[v6.6] INFO: task hung in migrate_pages_batch

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fe9731e10004 Linux 6.6.105
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17fd7562580000
kernel config: https://syzkaller.appspot.com/x/.config?x=dac93b93d3de2741
dashboard link: https://syzkaller.appspot.com/bug?extid=11c27a224629323c5c63
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0909010aa8be/disk-fe9731e1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c6e9748af850/vmlinux-fe9731e1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ddc345b8caaf/bzImage-fe9731e1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+11c27a...@syzkaller.appspotmail.com

INFO: task syz.1.1176:8736 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.1176 state:D stack:22768 pid:8736 ppid:5784 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5380 [inline]
__schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
schedule+0xbd/0x170 kernel/sched/core.c:6773
io_schedule+0x80/0xd0 kernel/sched/core.c:9022
folio_wait_bit_common+0x6eb/0xf70 mm/filemap.c:1329
migrate_folio_unmap mm/migrate.c:1162 [inline]
migrate_pages_batch+0x1364/0x3430 mm/migrate.c:1672
migrate_pages_sync mm/migrate.c:1865 [inline]
migrate_pages+0x2085/0x2920 mm/migrate.c:1947
compact_zone+0x21df/0x44b0 mm/compaction.c:2515
compact_node+0x167/0x2b0 mm/compaction.c:2807
compact_nodes mm/compaction.c:2820 [inline]
sysctl_compaction_handler+0xf9/0x1a0 mm/compaction.c:2866
proc_sys_call_handler+0x45d/0x6d0 fs/proc/proc_sysctl.c:599
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x79a/0xc70 fs/read_write.c:860
iter_file_splice_write+0x66f/0xc50 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+0x2f0/0x870 fs/splice.c:1088
do_splice_direct+0x1b7/0x2c0 fs/splice.c:1194
do_sendfile+0x5dc/0xf70 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1316 [inline]
__se_sys_sendfile64+0xda/0x190 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5f43b8eba9
RSP: 002b:00007f5f449ea038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f5f43dd5fa0 RCX: 00007f5f43b8eba9
RDX: 00002000000000c0 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00007f5f43c11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5f43dd6038 R14: 00007f5f43dd5fa0 R15: 00007ffc026f5fb8
</TASK>

Showing all locks held in the system:
2 locks held by kworker/u4:1/12:
1 lock held by khungtaskd/29:
#0: ffffffff8cd2fc20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2fc20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2fc20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
1 lock held by klogd/5146:
#0: ffff8880b8e3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xad/0x140 kernel/sched/core.c:566
2 locks held by getty/5553:
#0: ffff88802cf740a0 (&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+0x425/0x1380 drivers/tty/n_tty.c:2217
1 lock held by udevd/5777:
#0: ffff888021db04c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by udevd/5779:
#0: ffff888021bd34c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by syz-executor/5788:
1 lock held by syz.1.1176/8736:
#0: ffff88807bde2418 (sb_writers#3){.+.+}-{0:0}, at: do_sendfile+0x5b9/0xf70 fs/read_write.c:1253
1 lock held by syz-executor/11284:
1 lock held by syz.4.2173/11485:
#0: ffffffff8cd35ac0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x580 kernel/rcu/tree.c:4089

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x39b/0x3d0 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+0xf41/0xf80 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 11491 Comm: syz.3.2175 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:lockdep_recursion_finish kernel/locking/lockdep.c:467 [inline]
RIP: 0010:lock_acquire+0x19b/0x410 kernel/locking/lockdep.c:5756
Code: c1 4c 89 ef 8b 74 24 1c 89 da 48 8b 4c 24 20 4c 8b 44 24 30 6a 00 6a 00 6a 00 ff 75 10 ff 74 24 48 e8 b9 03 00 00 48 83 c4 28 <48> c7 c7 20 cc aa 8a e8 89 2d 07 09 b8 ff ff ff ff 65 0f c1 05 94
RSP: 0018:ffffc90004177b20 EFLAGS: 00000092
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff81671900
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90da5530
RBP: ffffc90004177c30 R08: dffffc0000000000 R09: 1ffffffff21b4aa6
R10: dffffc0000000000 R11: fffffbfff21b4aa7 R12: 1ffff9200082ef70
R13: ffff88802422d720 R14: 0000000000000246 R15: dffffc0000000000
FS: 00007fe04c7d56c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000003b5030 CR3: 000000002ee80000 CR4: 00000000003526e0
Call Trace:
<TASK>
__might_fault+0xc6/0x120 mm/memory.c:5946
do_recvmmsg+0x389/0x7d0 net/socket.c:2956
__sys_recvmmsg net/socket.c:3029 [inline]
__do_sys_recvmmsg net/socket.c:3052 [inline]
__se_sys_recvmmsg net/socket.c:3045 [inline]
__x64_sys_recvmmsg+0x191/0x240 net/socket.c:3045
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe04e58eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe04c7d5038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fe04e7d6090 RCX: 00007fe04e58eba9
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007fe04e611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe04e7d6128 R14: 00007fe04e7d6090 R15: 00007fffaf559b58
</TASK>


---
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