Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback

[syzbot <syzbot+0b74d367d6e80661d6df@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in v9fs_evict_inode

INFO: task syz-executor:5811 blocked for more than 143 seconds.
      Not tainted 6.11.0-rc1-syzkaller-00154-gc0ecd6388360-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:23952 pid:5811  tgid:5811  ppid:1      flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5188 [inline]
 __schedule+0xe37/0x5490 kernel/sched/core.c:6529
 __schedule_loop kernel/sched/core.c:6606 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6621
 netfs_wait_for_outstanding_io include/linux/netfs.h:535 [inline]
 v9fs_evict_inode+0x271/0x310 fs/9p/vfs_inode.c:351
 evict+0x2ed/0x6c0 fs/inode.c:669
 dispose_list+0x117/0x1e0 fs/inode.c:712
 evict_inodes+0x34e/0x450 fs/inode.c:762
 generic_shutdown_super+0xb5/0x3d0 fs/super.c:627
 kill_anon_super+0x3a/0x60 fs/super.c:1237
 v9fs_kill_super+0x3d/0xa0 fs/9p/vfs_super.c:193
 deactivate_locked_super+0xbe/0x1a0 fs/super.c:473
 deactivate_super+0xde/0x100 fs/super.c:506
 cleanup_mnt+0x222/0x450 fs/namespace.c:1373
 task_work_run+0x14e/0x250 kernel/task_work.c:228
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7b6a1786e7
RSP: 002b:00007ffeeb983478 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f7b6a1786e7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffeeb983530
RBP: 00007ffeeb983530 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffeeb9845b0
R13: 00007f7b6a1e4784 R14: 0000000000028c1d R15: 00007ffeeb9845f0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/40:
 #0: ffffffff8ddb53a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
 #0: ffffffff8ddb53a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8ddb53a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x75/0x340 kernel/locking/lockdep.c:6620
2 locks held by getty/5135:
 #0: ffff8880235fb0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900000db2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xfc8/0x1490 drivers/tty/n_tty.c:2211
1 lock held by syz-executor/5811:
 #0: ffff888020a800e0 (&type->s_umount_key#67){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff888020a800e0 (&type->s_umount_key#67){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff888020a800e0 (&type->s_umount_key#67){+.+.}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
2 locks held by syz.0.4336/14555:
 #0: ffffffff8ec222b8 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x14d/0x1370 drivers/misc/vmw_vmci/vmci_queue_pair.c:2095
 #1: ffffffff8ddc0b38 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock+0x282/0x3b0 kernel/rcu/tree_exp.h:296

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 40 Comm: khungtaskd Not tainted 6.11.0-rc1-syzkaller-00154-gc0ecd6388360-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 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+0xf4e/0x1280 kernel/hung_task.c:379
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 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 0,2-3:
NMI backtrace for cpu 3 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 3 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:106 [inline]
NMI backtrace for cpu 3 skipped: idling at default_idle+0xf/0x20 arch/x86/kernel/process.c:742
NMI backtrace for cpu 2 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 2 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:106 [inline]
NMI backtrace for cpu 2 skipped: idling at default_idle+0xf/0x20 arch/x86/kernel/process.c:742
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:106 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xf/0x20 arch/x86/kernel/process.c:742


Tested on:

commit:         c0ecd638 Merge tag 'pci-v6.11-fixes-1' of git://git.ke..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1265c113980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8da8b059e43c5370
dashboard link: https://syzkaller.appspot.com/bug?extid=0b74d367d6e80661d6df
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12a5c113980000