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

[Raghavendra Gowdappa]

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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