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    SubjectRe: [PATCH 2/8] cfq-iosched: fix async oom queue handling
    Date
    Tejun Heo <tj@kernel.org> writes:

    > 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.

    Good catch.

    Reviewed-by: Jeff Moyer <jmoyer@redhat.com>


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