[f2fs-dev] [syzbot] [f2fs?] INFO: task hung in f2fs_llseek

[syzbot <syzbot+942fb6ce3ac2843a1420@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3957a5720157 Merge tag 'cgroup-for-6.17-rc2-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13e20c42580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
dashboard link: https://syzkaller.appspot.com/bug?extid=942fb6ce3ac2843a1420
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17db07bc580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12f62a34580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c5cbe8650b9a/disk-3957a572.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/51911bea9855/vmlinux-3957a572.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b07279b5fcc2/bzImage-3957a572.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/f35e0e9a079a/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10a5dfa2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+942fb6ce3ac2843a1420@syzkaller.appspotmail.com

INFO: task syz.1.23:6086 blocked for more than 143 seconds.
      Tainted: G        W           syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.23        state:D stack:29352 pid:6086  tgid:6081  ppid:6062   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7339
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1e04/0x25e0 kernel/locking/rtmutex.c:1760
 __rwbase_read_lock+0xbc/0x180 kernel/locking/rwbase_rt.c:114
 rwbase_read_lock kernel/locking/rwbase_rt.c:147 [inline]
 __down_read kernel/locking/rwsem.c:1466 [inline]
 down_read+0x127/0x1f0 kernel/locking/rwsem.c:1539
 inode_lock_shared include/linux/fs.h:884 [inline]
 f2fs_seek_block fs/f2fs/file.c:458 [inline]
 f2fs_llseek+0x1e5/0x1840 fs/f2fs/file.c:545
 vfs_llseek fs/read_write.c:389 [inline]
 ksys_lseek fs/read_write.c:402 [inline]
 __do_sys_lseek fs/read_write.c:412 [inline]
 __se_sys_lseek fs/read_write.c:410 [inline]
 __x64_sys_lseek+0x155/0x1f0 fs/read_write.c:410
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7c9077ebe9
RSP: 002b:00007f7c8fdcd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 00007f7c909a6090 RCX: 00007f7c9077ebe9
RDX: 0000000000000004 RSI: 0000000000000008 RDI: 0000000000000004
RBP: 00007f7c90801e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7c909a6128 R14: 00007f7c909a6090 R15: 00007fffeb5fe138
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 39 Comm: khungtaskd Tainted: G        W           syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:328 [inline]
 watchdog+0xf93/0xfe0 kernel/hung_task.c:491
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6274 Comm: syz.3.43 Tainted: G        W           syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:unwind_next_frame+0x175d/0x2390 arch/x86/kernel/unwind_orc.c:648
Code: 28 84 c0 0f 85 19 0b 00 00 48 89 d0 48 c1 e8 03 0f b6 04 28 84 c0 0f 85 2b 0b 00 00 48 0f bf 03 49 01 c4 49 8d 56 40 4c 89 f7 <4c> 89 e6 eb 5d 49 8d 5e 40 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08
RSP: 0018:ffffc90003b06438 EFLAGS: 00000283
RAX: fffffffffffffff0 RBX: ffffffff8fd32106 RCX: 0000000000000000
RDX: ffffc90003b06548 RSI: 0000000000000001 RDI: ffffc90003b06508
RBP: dffffc0000000000 R08: ffffc90003b06567 R09: 0000000000000000
R10: ffffc90003b06558 R11: fffff52000760cad R12: ffffc90003b069d0
R13: ffffc90003b06558 R14: ffffc90003b06508 R15: 1ffffffff1fa6421
FS:  00007f0008c3c6c0(0000) GS:ffff8881268c4000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8cae82bf98 CR3: 000000005b1bc000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 slab_free_hook mm/slub.c:2378 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x3ef/0x510 mm/slub.c:4782
 f2fs_read_end_io+0x398/0x9d0 fs/f2fs/data.c:-1
 f2fs_submit_page_read+0x116/0x190 fs/f2fs/data.c:1110
 f2fs_get_read_data_folio+0x4a4/0x7d0 fs/f2fs/data.c:1268
 gc_data_segment fs/f2fs/gc.c:1641 [inline]
 do_garbage_collect+0x3898/0x6410 fs/f2fs/gc.c:1826
 f2fs_gc+0xca9/0x2580 fs/f2fs/gc.c:1931
 f2fs_balance_fs+0x5fb/0x7f0 fs/f2fs/segment.c:466
 f2fs_map_blocks+0x345f/0x4130 fs/f2fs/data.c:1792
 f2fs_expand_inode_data+0x5b1/0xa60 fs/f2fs/file.c:1923
 f2fs_fallocate+0x4f8/0x990 fs/f2fs/file.c:2026
 vfs_fallocate+0x672/0x7f0 fs/open.c:342
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl+0x61d/0x780 fs/ioctl.c:-1
 do_vfs_ioctl+0xb36/0x1440 fs/ioctl.c:577
 __do_sys_ioctl fs/ioctl.c:596 [inline]
 __se_sys_ioctl+0x82/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f000960ebe9
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:00007f0008c3c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0009836180 RCX: 00007f000960ebe9
RDX: 0000200000000000 RSI: 0000000040305828 RDI: 0000000000000005
RBP: 00007f0009691e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0009836218 R14: 00007f0009836180 R15: 00007ffee123ac28
 </TASK>


---
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