[Gluster-devel] fstat problems when killing with stat prefetch turned on

[Miklós Fokin]

Thanks for the response.
We didn't have the options set that the first two reviews were about.
The third was about changes to performance.readdir-ahead.
I turned this feature off today with prefetch being turned on on my 
computer, and the bug still appeared, so I would think that the commit 
would not fix it either.

Best regards,
Miklós


On 04/25/2017 01:26 PM, Raghavendra Gowdappa wrote:
> Recently we had worked on some patches to ensure correct stats are returned.
>
> https://review.gluster.org/15759
> https://review.gluster.org/15659
> https://review.gluster.org/16419
>
> Referring to these patches and bugs associated with them might give you some insight into the nature of the problem. The major culprit was interaction between readdir-ahead and stat-prefetch. So, the issue you are seeing might be addressed by these patches.
>
> ----- Original Message -----
>> From: "Miklós Fokin" <miklos.fokin at appeartv.com>
>> To: gluster-devel at gluster.org
>> Sent: Tuesday, April 25, 2017 3:42:52 PM
>> Subject: [Gluster-devel] fstat problems when killing with stat prefetch	turned on
>>
>> Hello,
>>
>> I tried reproducing the problem that Mateusz Slupny was experiencing
>> before (stat returning bad st_size value on self-healing) on my own
>> computer with only 3 bricks (one being an arbiter) on 3.10.0.
>> The result with such a small setup was that the bug appeared both on
>> killing and during the self-healing process, but only rarely (once in
>> hundreds of tries) and only with performance.stat-prefetch turned on.
>> This might be a completely different issue as on the setup Matt was
>> using, he could reproduce it with the mentioned option being off, it
>> always happened but only during recovery, not after killing.
>> I did submit a bug report about this:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1444892.
>>
>> The problem is as Matt wrote is that this causes data corruption if one
>> is to use the returned size on writing.
>> Could I get some pointers as to what parts of the gluster code I should
>> be looking at to figure out what the problem might be?
>>
>> Thanks in advance,
>> Miklós
>>
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