From: NeilBrown <neilb@suse.de>
Date: Mon, 4 Mar 2013 01:37:14 +0000 (+1100)
Subject: md/raid5: schedule_construction should abort if nothing to do.
X-Git-Tag: v3.9-rc4~2^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ce7d363aaf1e28be8406a2976220944ca487e8ca;p=pandora-kernel.git

md/raid5: schedule_construction should abort if nothing to do.

Since commit 1ed850f356a0a422013846b5291acff08815008b
    md/raid5: make sure to_read and to_write never go negative.

It has been possible for handle_stripe_dirtying to be called
when there isn't actually any work to do.
It then calls schedule_reconstruction() which will set R5_LOCKED
on the parity block(s) even when nothing else is happening.
This then causes problems in do_release_stripe().

So add checks to schedule_reconstruction() so that if it doesn't
find anything to do, it just aborts.

This bug was introduced in v3.7, so the patch is suitable
for -stable kernels since then.

Cc: stable@vger.kernel.org (v3.7+)
Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
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