Re: [syzbot] [bcachefs?] INFO: task hung in bch2_fs_read_only_work

[syzbot <syzbot+8996d8f176cf946ef641@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    f06ce441457d Merge tag 'loongarch-fixes-6.10-1' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17802a16980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=eb72437243175f22
dashboard link: https://syzkaller.appspot.com/bug?extid=8996d8f176cf946ef641
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=164255f2980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16174432980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/00ecb7bdd1a8/disk-f06ce441.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3926ab949197/vmlinux-f06ce441.xz
kernel image: https://storage.googleapis.com/syzbot-assets/36849eea4fc5/bzImage-f06ce441.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/bfad9a4a2dc4/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8996d8f176cf946ef641@syzkaller.appspotmail.com

INFO: task kworker/1:0:25 blocked for more than 143 seconds.
      Not tainted 6.10.0-rc2-syzkaller-00007-gf06ce441457d #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:0     state:D
 stack:26248 pid:25    tgid:25    ppid:2      flags:0x00004000
Workqueue: events_long bch2_fs_read_only_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5408 [inline]
 __schedule+0x1796/0x49d0 kernel/sched/core.c:6745
 __schedule_loop kernel/sched/core.c:6822 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6837
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6894
 rwsem_down_write_slowpath+0xeeb/0x13b0 kernel/locking/rwsem.c:1178
 __down_write_common+0x1af/0x200 kernel/locking/rwsem.c:1306
 bch2_fs_read_only_work+0x25/0x40 fs/bcachefs/super.c:392
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/1:0/25:
 #0: ffff888015081148 ((wq_completion)events_long){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3206 [inline]
 #0: ffff888015081148 ((wq_completion)events_long){+.+.}-{0:0}, at: process_scheduled_works+0x90a/0x1830 kernel/workqueue.c:3312
 #1: ffffc900001f7d00 ((work_completion)(&c->read_only_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3207 [inline]
 #1: ffffc900001f7d00 ((work_completion)(&c->read_only_work)){+.+.}-{0:0}, at: process_scheduled_works+0x945/0x1830 kernel/workqueue.c:3312
 #2: ffff888075980278 (&c->state_lock){+.+.}-{3:3}, at: bch2_fs_read_only_work+0x25/0x40 fs/bcachefs/super.c:392
1 lock held by khungtaskd/30:
 #0: ffffffff8e333f60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #0: ffffffff8e333f60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #0: ffffffff8e333f60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
5 locks held by kworker/u8:2/35:
1 lock held by klogd/4522:
2 locks held by getty/4833:
 #0: ffff88802fb4a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2201
3 locks held by syz-executor131/5078:

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

NMI backtrace for cpu 1
CPU: 1 PID: 30 Comm: khungtaskd Not tainted 6.10.0-rc2-syzkaller-00007-gf06ce441457d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
 watchdog+0xfde/0x1020 kernel/hung_task.c:379
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4515 Comm: syslogd Not tainted 6.10.0-rc2-syzkaller-00007-gf06ce441457d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:skb_ext_put include/linux/skbuff.h:4688 [inline]
RIP: 0010:skb_release_head_state+0x19d/0x250 net/core/skbuff.c:1165
Code: 4e f8 eb 16 31 ff 89 ee e8 80 50 4e f8 85 ed 0f 8e 8a 00 00 00 e8 33 4c 4e f8 49 8d 5e 7f 48 89 d8 48 c1 e8 03 42 0f b6 04 20 <84> c0 0f 85 84 00 00 00 0f b6 1b 31 ff 89 de e8 0f 4f 4e f8 85 db
RSP: 0018:ffffc90004907908 EFLAGS: 00000a07
RAX: 0000000000000000 RBX: ffff88802e28ecff RCX: ffff88807d280000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8947c904 R09: 1ffff11003ca5853
R10: dffffc0000000000 R11: ffffed1003ca5854 R12: dffffc0000000000
R13: ffff88802e28ec80 R14: ffff88802e28ec80 R15: ffff88802e28ece0
FS:  00007fa63915c380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e2897e7600 CR3: 000000002dc2c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 skb_release_all net/core/skbuff.c:1171 [inline]
 __kfree_skb net/core/skbuff.c:1187 [inline]
 consume_skb+0x7b/0x160 net/core/skbuff.c:1409
 __unix_dgram_recvmsg+0xcea/0x12f0 net/unix/af_unix.c:2474
 sock_recvmsg_nosec net/socket.c:1046 [inline]
 sock_recvmsg+0x22f/0x280 net/socket.c:1068
 sock_read_iter+0x2ca/0x3e0 net/socket.c:1138
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x9c4/0xbd0 fs/read_write.c:476
 ksys_read+0x1a0/0x2c0 fs/read_write.c:619
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa6392b0b6a
Code: 00 3d 00 00 41 00 75 0d 50 48 8d 3d 2d 08 0a 00 e8 ea 7d 01 00 31 c0 e9 07 ff ff ff 64 8b 04 25 18 00 00 00 85 c0 75 1b 0f 05 <48> 3d 00 f0 ff ff 76 6c 48 8b 15 8f a2 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffec9bf54e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa6392b0b6a
RDX: 00000000000000ff RSI: 000055cf5b545950 RDI: 0000000000000000
RBP: 000055cf5b545910 R08: 0000000000000001 R09: 0000000000000000
R10: 00007fa63944f3a3 R11: 0000000000000246 R12: 000055cf5b54598a
R13: 000055cf5b545950 R14: 0000000000000000 R15: 00007fa639493a80
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.151 msecs


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