tree 4b30989af492f003a7bdb9534951f47f5341273d
parent 4ebc1c61d6185604c97fd0b0355ab668052044ab
author Tejun Heo <tj@kernel.org> 1439934898 -0700
committer Jens Axboe <axboe@fb.com> 1439938155 -0700

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>