cfq-iosched: don't delay queue kick for a merged request

[mirror_ubuntu-bionic-kernel.git] / block / cfq-iosched.c

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index cba8a5d91bfa97dba6490988cc4ee7a7d802265c..56e9d8503cf1ddc5d67113820b9ac1c069b701e7 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1903,10 +1903,17 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 * Remember that we saw a request from this process, but
                 * don't start queuing just yet. Otherwise we risk seeing lots
                 * of tiny requests, because we disrupt the normal plugging
-                * and merging.
+                * and merging. If the request is already larger than a single
+                * page, let it rip immediately. For that case we assume that
+                * merging is already done.
                 */
-               if (cfq_cfqq_wait_request(cfqq))
+               if (cfq_cfqq_wait_request(cfqq)) {
+                       if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE) {
+                               del_timer(&cfqd->idle_slice_timer);
+                               blk_start_queueing(cfqd->queue);
+                       }
                        cfq_mark_cfqq_must_dispatch(cfqq);
+               }
        } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
                /*
                 * not the active queue - expire current slice if it is