[syzbot] [gfs2?] INFO: task hung in writeback_iter (3)

[syzbot <syzbot+1e3ff4b07c16ca0f6fe2@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    7fa4d8dc380f Add linux-next specific files for 20250821
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=130beef0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5d054fcd55656377
dashboard link: https://syzkaller.appspot.com/bug?extid=1e3ff4b07c16ca0f6fe2
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=10339c42580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1668e462580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a843be98ab42/disk-7fa4d8dc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/17b718892b67/vmlinux-7fa4d8dc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8939424b4b54/bzImage-7fa4d8dc.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6c5d1c428942/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=150beef0580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1e3ff4b07c16ca0f6fe2@syzkaller.appspotmail.com

INFO: task syz.0.17:6037 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:25096 pid:6037  tgid:6037  ppid:5973   task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 io_schedule+0x80/0xd0 kernel/sched/core.c:7903
 folio_wait_bit_common+0x6b0/0xb90 mm/filemap.c:1317
 folio_lock include/linux/pagemap.h:1139 [inline]
 writeback_get_folio mm/page-writeback.c:2468 [inline]
 writeback_iter+0x8d8/0x12a0 mm/page-writeback.c:2562
 iomap_writepages+0x14d/0x2d0 fs/iomap/buffered-io.c:1761
 gfs2_writepages+0x177/0x250 fs/gfs2/aops.c:175
 do_writepages+0x32e/0x550 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 __filemap_fdatawrite mm/filemap.c:425 [inline]
 filemap_fdatawrite+0x199/0x240 mm/filemap.c:430
 gfs2_ordered_write fs/gfs2/log.c:733 [inline]
 gfs2_log_flush+0x966/0x24c0 fs/gfs2/log.c:1102
 gfs2_trans_end+0x37c/0x570 fs/gfs2/trans.c:158
 gfs2_page_mkwrite+0x14a8/0x1910 fs/gfs2/file.c:535
 do_page_mkwrite+0x14d/0x310 mm/memory.c:3489
 do_shared_fault mm/memory.c:5779 [inline]
 do_fault mm/memory.c:5841 [inline]
 do_pte_missing mm/memory.c:4362 [inline]
 handle_pte_fault mm/memory.c:6182 [inline]
 __handle_mm_fault+0x1916/0x5400 mm/memory.c:6323
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6492
 do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x7f97632550b3
RSP: 002b:00007ffef0bb04e0 EFLAGS: 00010246
RAX: 0000200000000180 RBX: 0000000000000008 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005555685083c8
RBP: 00007ffef0bb05e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00007f97635b5fac
R13: 00007f97635b5fa0 R14: fffffffffffffffe R15: 0000000000000006
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
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:332 [inline]
 watchdog+0xf60/0xfa0 kernel/hung_task.c:495
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148
 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: 6836 Comm: syz.1.269 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:dsp_cmx_send+0x0/0x1b40 drivers/isdn/mISDN/dsp_cmx.c:1618
Code: 3b aa f9 48 ba 00 00 00 00 00 fc ff df e9 09 f2 ff ff 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 55 41 57 41 56 41 55 41 54 53 48 81 ec e0 00 00 00 e8
RSP: 0018:ffffc90000a08b98 EFLAGS: 00000246
RAX: ffffffff81ae4d15 RBX: 0000000000000101 RCX: ffff88801d78da00
RDX: 0000000000000100 RSI: ffffffff8c035860 RDI: ffffffff9a057420
RBP: ffffc90000a08c90 R08: ffffffff8fc40337 R09: 1ffffffff1f88066
R10: dffffc0000000000 R11: ffffffff8879fcb0 R12: 1ffff92000141178
R13: ffffffff9a057420 R14: 0000000000000001 R15: 0000000000000001
FS:  0000555565d25500(0000) GS:ffff888125aff000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4ea15ff000 CR3: 0000000027184000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 call_timer_fn+0x17b/0x5f0 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers kernel/time/timer.c:2372 [inline]
 __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
 run_timer_base kernel/time/timer.c:2393 [inline]
 run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:console_trylock_spinning kernel/printk/printk.c:2061 [inline]
RIP: 0010:vprintk_emit+0x58f/0x7a0 kernel/printk/printk.c:2449
Code: 85 32 01 00 00 e8 a1 81 1f 00 41 89 df 4d 85 f6 48 8b 1c 24 75 07 e8 90 81 1f 00 eb 06 e8 89 81 1f 00 fb 48 c7 c7 80 02 33 8e <31> f6 ba 01 00 00 00 31 c9 41 b8 01 00 00 00 45 31 c9 53 e8 b9 35
RSP: 0018:ffffc90004a8ed80 EFLAGS: 00000293
RAX: ffffffff81a10d47 RBX: ffffffff81a10c04 RCX: ffff88801d78da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8e330280
RBP: ffffc90004a8ee90 R08: ffffffff8fc40337 R09: 1ffffffff1f88066
R10: dffffc0000000000 R11: fffffbfff1f88067 R12: dffffc0000000000
R13: 1ffff92000951db4 R14: 0000000000000200 R15: 000000000000002f
 _printk+0xcf/0x120 kernel/printk/printk.c:2475
 set_capacity_and_notify+0x208/0x2d0 block/genhd.c:93
 loop_set_size+0x44/0xb0 drivers/block/loop.c:214
 loop_configure+0x9f4/0xe50 drivers/block/loop.c:1071
 lo_ioctl+0x810/0x1b30 drivers/block/loop.c:-1
 blkdev_ioctl+0x5a8/0x6d0 block/ioctl.c:705
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4ea958e7eb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007ffc529a9be0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f4ea958e7eb
RDX: 0000000000000003 RSI: 0000000000004c00 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 000000000001f78a
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffc529a9d10 R14: 00007ffc529a9cd0 R15: 00007f4ea0600000
 </TASK>


---
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