[Virtio-fs] Unbreakable loop in fuse_fill_write_pages()

[Harry G. Coin]

On 10/13/20 2:12 PM, Qian Cai wrote:
> On Tue, 2020-10-13 at 14:58 -0400, Vivek Goyal wrote:
>> I am wondering if virtiofsd still alive and responding to requests? I
>> see another task which is blocked on getdents() for more than 120s.
>>
>> [10580.142571][  T348] INFO: task trinity-c36:254165 blocked for more than 123
>> +seconds.
>> [10580.143924][  T348]       Tainted: G           O	 5.9.0-next-20201013+ #2
>> [10580.145158][  T348] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>> +disables this message.
>> [10580.146636][  T348] task:trinity-c36     state:D stack:26704 pid:254165
>> ppid:
>> +87180 flags:0x00000004
>> [10580.148260][  T348] Call Trace:
>> [10580.148789][  T348]  __schedule+0x71d/0x1b50
>> [10580.149532][  T348]  ? __sched_text_start+0x8/0x8
>> [10580.150343][  T348]  schedule+0xbf/0x270
>> [10580.151044][  T348]  schedule_preempt_disabled+0xc/0x20
>> [10580.152006][  T348]  __mutex_lock+0x9f1/0x1360
>> [10580.152777][  T348]  ? __fdget_pos+0x9c/0xb0
>> [10580.153484][  T348]  ? mutex_lock_io_nested+0x1240/0x1240
>> [10580.154432][  T348]  ? find_held_lock+0x33/0x1c0
>> [10580.155220][  T348]  ? __fdget_pos+0x9c/0xb0
>> [10580.155934][  T348]  __fdget_pos+0x9c/0xb0
>> [10580.156660][  T348]  __x64_sys_getdents+0xff/0x230
>>
>> May be virtiofsd crashed and hence no requests are completing leading
>> to a hard lockup?
> No, it was not crashed. After I had to forcibly close the guest, the virtiofsd
> daemon will exit normally. However, I can't tell exactly if the virtiofsd daemon
> was still functioning normally. I'll enable the debug and retry to see if there
> is anything interesting.

Though it's likely not related, randomly but perhaps twice every three
days I notice when a VM is stopped, it can't be restarted because the
virtiofsd instance from the previous run hasn't exited and won't exit no
matter how long a delay absent a kill -KILL.   I'm not sure how to debug
or get info on that.


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