From: NeilBrown <neilb@suse.de>
Date: Wed, 31 Mar 2010 00:21:44 +0000 (+1100)
Subject: md/raid1: delay reads that could overtake behind-writes.
X-Git-Tag: v2.6.35-rc1~440^2~15
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e555190d82c0f58e825e3cbd9e6ebe2e7ac713bd;p=pandora-kernel.git

md/raid1: delay reads that could overtake behind-writes.

When a raid1 array is configured to support write-behind
on some devices, it normally only reads from other devices.
If all devices are write-behind (because the rest have failed)
it is possible for a read request to be serviced before a
behind-write request, which would appear as data corruption.

So when forced to read from a WriteMostly device, wait for any
write-behind to complete, and don't start any more behind-writes.

Signed-off-by: NeilBrown <neilb@suse.de>
---

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