From: Steven Whitehouse <swhiteho@redhat.com>
Date: Mon, 23 Jun 2014 13:43:32 +0000 (+0100)
Subject: GFS2: Fix race in glock lru glock disposal
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~276^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=94a09a3999ee978e097b5aad74034ed43bae56db;p=pandora-kernel.git

GFS2: Fix race in glock lru glock disposal

We must not leave items on the LRU list with GLF_LOCK set, since
they can be removed if the glock is brought back into use, which
may then potentially result in a hang, waiting for GLF_LOCK to
clear.

It doesn't happen very often, since it requires a glock that has
not been used for a long time to be brought back into use at the
same moment that the shrinker is part way through disposing of
glocks.

The fix is to set GLF_LOCK at a later time, when we already know
that the other locks can be obtained. Also, we now only release
the lru_lock in case a resched is needed, rather than on every
iteration.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
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