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@@ -2517,6 +2517,45 @@ void blk_account_io_start(struct request *rq, bool new_io)
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part_stat_unlock();
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}
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+static struct request *elv_next_request(struct request_queue *q)
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+{
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+ struct request *rq;
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+ struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
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+
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+ WARN_ON_ONCE(q->mq_ops);
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+
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+ while (1) {
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+ if (!list_empty(&q->queue_head)) {
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+ rq = list_entry_rq(q->queue_head.next);
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+ return rq;
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+ }
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+
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+ /*
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+ * Flush request is running and flush request isn't queueable
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+ * in the drive, we can hold the queue till flush request is
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+ * finished. Even we don't do this, driver can't dispatch next
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+ * requests and will requeue them. And this can improve
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+ * throughput too. For example, we have request flush1, write1,
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+ * flush 2. flush1 is dispatched, then queue is hold, write1
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+ * isn't inserted to queue. After flush1 is finished, flush2
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+ * will be dispatched. Since disk cache is already clean,
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+ * flush2 will be finished very soon, so looks like flush2 is
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+ * folded to flush1.
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+ * Since the queue is hold, a flag is set to indicate the queue
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+ * should be restarted later. Please see flush_end_io() for
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+ * details.
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+ */
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+ if (fq->flush_pending_idx != fq->flush_running_idx &&
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+ !queue_flush_queueable(q)) {
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+ fq->flush_queue_delayed = 1;
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+ return NULL;
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+ }
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+ if (unlikely(blk_queue_bypass(q)) ||
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+ !q->elevator->type->ops.sq.elevator_dispatch_fn(q, 0))
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+ return NULL;
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+ }
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+}
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+
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/**
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* blk_peek_request - peek at the top of a request queue
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* @q: request queue to peek at
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@@ -2538,8 +2577,7 @@ struct request *blk_peek_request(struct request_queue *q)
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lockdep_assert_held(q->queue_lock);
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WARN_ON_ONCE(q->mq_ops);
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- while ((rq = __elv_next_request(q)) != NULL) {
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-
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+ while ((rq = elv_next_request(q)) != NULL) {
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rq = blk_pm_peek_request(q, rq);
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if (!rq)
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break;
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