From: Tejun Heo <tj@kernel.org>
Date: Tue, 18 Aug 2015 21:54:58 +0000 (-0700)
Subject: cfq-iosched: fix async oom queue handling
X-Git-Tag: omap-for-v4.3/fixes-rc1~35^2~38
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=95e5d6f62693f27d9011ec307eb32c6126314ea3;p=pandora-kernel.git

cfq-iosched: fix async oom queue handling

Async cfqq's (cfq_queue's) are shared across cfq_data.  When
cfq_get_queue() obtains a new queue from cfq_find_alloc_queue(), it
stashes the pointer in cfq_data and reuses it from then on; however,
the function doesn't consider that cfq_find_alloc_queue() may return
the oom_cfqq under memory pressure and installs the returned queue
unconditionally.

If the oom_cfqq is installed as an async cfqq, cfq_set_request() will
continue calling cfq_get_queue() hoping to replace it with a proper
queue; however, cfq_get_queue() will keep returning the cached queue
for the slot - the oom_cfqq.

Fix it by skipping caching if the queue is the oom one.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

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