Miklos, Thanks for this patch.
Team will review this, and update you on if this is good fix.On Thu, May 4, 2017 at 6:59 PM, Miklós Fokin <miklos.fokin@xxxxxxxxxxxx> wrote:
Sorry, missing lines from the attachment.
On 05/04/2017 03:24 PM, Miklós Fokin wrote:
Hello,
I seem to have discovered what caused half of the problem.
I did update the bug report with a more detailed description, but the short version is that the attached diff solves the issue when we get an fstat with a size of 0 after killing a brick (not letting the first update to fsync be from an arbiter).
My question is: should I make a review about it or should further needed changes be investigated first?
Best regards,
Miklós
On 04/26/2017 12:58 PM, Miklós Fokin wrote:
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@xxxxxxxxxxxx>
To: gluster-devel@xxxxxxxxxxx
Sent: Tuesday, April 25, 2017 3:42:52 PM
Subject: 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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