Re: [PATCH 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[Qu Wenruo <wqu@suse.de>]

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On 2019/1/10 下午9:53, Filipe Manana wrote:
[snip]
>>>> +# Workaround to handle killed workload with unreturned syscall
>>>> +sync
>>>
>>> I can't understand that comment, nor why the call to sync (probably
>>> most readers won't either).
>>> What do you mean by "unreturned syscall"? It hangs, blocked? Because
>>> of the deadlock? How does the sync makes it "return"?
>>
>> I mean normal "btrfs subvolume create/delete" ioctl syscalls.
>>
>>>
>>> When you say killed workload, you mean though the kill commands above?
>>> For all pids or just some in particular?
>>
>> For the workload, it will be a forked bash process, and then executing
>> "btrfs" program.
>> While "btrfs subvolume create/delete" could call ioctl and fall into
>> kernel space, kill/wait for the bash process could return before the
>> ioctl returned.
>>
>> So here we try to call sync which will commit current transaction, more
>> or less wait for unfinished "btrfs" ioctls to return.
>>
>> Or should I change to the more common loop of check "btrfs" process and
>> wait?
> 
> Doing something like the following seems to be what you need:
> 
> https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/commit/?id=d0ec5f5af9479137526b73b8b4f48ef028444ffc

Thanks a lot!

It's much better than my ugly workaround.

I'll update the patch to address all your comment.

Thanks,
Qu

> 
> 
>>
>> Thanks,
>> Qu
>>
>>>
>>>> +
>>>> +# success, all done
>>>> +echo "Silence is golden"
>>>> +
>>>> +status=0
>>>> +exit
>>>> diff --git a/tests/btrfs/179.out b/tests/btrfs/179.out
>>>> new file mode 100644
>>>> index 000000000000..cb9eba3d34b1
>>>> --- /dev/null
>>>> +++ b/tests/btrfs/179.out
>>>> @@ -0,0 +1,2 @@
>>>> +QA output created by 179
>>>> +Silence is golden
>>>> diff --git a/tests/btrfs/group b/tests/btrfs/group
>>>> index 04c0254aa4bf..46dd3c9523c2 100644
>>>> --- a/tests/btrfs/group
>>>> +++ b/tests/btrfs/group
>>>> @@ -181,3 +181,4 @@
>>>>  176 auto quick swap volume
>>>>  177 auto quick swap balance
>>>>  178 auto quick send
>>>> +179 auto qgroup dangerous
>>>> --
>>>> 2.20.1
>>>>
>>>
>>>
>>
> 
> 


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