From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: raid6 - data integrity issue - data mis-compare on rebuilding
 RAID 6 - with 100 Mb resync speed.
Date: Wed, 23 Apr 2014 17:07:55 +1000
Message-ID: <20140423170755.1aa92ba6@notabene.brown>
References: <13688C12F44C7C428726663F950CA2530972DC8C@venus.in.megatrends.com>
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To: Manibalan P <pmanibalan@amiindia.co.in>
Cc: linux-raid@vger.kernel.org, Dan Williams <dan.j.williams@intel.com>
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On Fri, 11 Apr 2014 17:41:12 +0530 "Manibalan P" <pmanibalan@amiindia.co.in>
wrote:

> Hi Neil,
>=20
> Also, I found the data corruption issue on RHEL 6.5.
>=20
> For your kind attention, I up-ported the md code [raid5.c + raid5.h]
> from FC11 kernel to CentOS 6.4, and there is no mis-compare with the
> up-ported code.

This narrows it down to between 2.6.29 and 2.6.32 - is that correct?

So it is probably the change to RAID6 to support async parity calculations.

Looking at the code always makes my head spin.

Dan : have you any ideas?

It seems that writing to a double-degraded RAID6 while it is recovering to
a space can trigger data corruption.

2.6.29 works
2.6.32 doesn't
3.8.0 still doesn't.

I suspect async parity calculations.

NeilBrown

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