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    SubjectRe: [PATCH block/for-next] block: don't call blk_drain_queue() if elevator is not up
    On Nov 03 Tejun Heo wrote:
    > blk_cleanup_queue() may be called before elevator is set up on a
    > queue which triggers the following oops.
    [...]
    > --- a/block/blk-core.c
    > +++ b/block/blk-core.c
    > @@ -407,8 +407,13 @@ void blk_cleanup_queue(struct request_queue *q)
    > spin_unlock_irq(lock);
    > mutex_unlock(&q->sysfs_lock);
    >
    > - /* drain all requests queued before DEAD marking */
    > - blk_drain_queue(q, true);
    > + /*
    > + * Drain all requests queued before DEAD marking. The caller might
    > + * be trying to tear down @q before its elevator is initialized, in
    > + * which case we don't want to call into draining.
    > + */
    > + if (q->elevator)
    > + blk_drain_queue(q, true);
    >
    > /* @q won't process any more request, flush async actions */
    > del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);

    What prevents elevator_attach to be called and requests to be inserted
    between 'if (q-elevator)' and 'blk_put_queue(q)'?
    --
    Stefan Richter
    -=====-==-== =-== --=--
    http://arcgraph.de/sr/


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