From: Tejun Heo <tj@kernel.org>
Date: Tue, 13 Dec 2011 23:33:38 +0000 (+0100)
Subject: block, cfq: fix race condition in cic creation path and tighten locking
X-Git-Tag: v3.3-rc1~49^2~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=216284c352a0061f5b20acff2c4e50fb43fea183;p=pandora-kernel.git

block, cfq: fix race condition in cic creation path and tighten locking

cfq_get_io_context() would fail if multiple tasks race to insert cic's
for the same association.  This patch restructures
cfq_get_io_context() such that slow path insertion race is handled
properly.

Note that the restructuring also makes cfq_get_io_context() called
under queue_lock and performs both ioc and cfqd insertions while
holding both ioc and queue locks.  This is part of on-going locking
tightening and will be used to simplify synchronization rules.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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