1 files changed, 17 insertions, 8 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 11efcf196e74..a4809de6fea6 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -177,6 +177,7 @@ struct cfq_queue {
 enum cfqq_state_flags {
         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
+        CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
         CFQ_CFQQ_FLAG_must_alloc,       /* must be allowed rq alloc */
         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
@@ -202,6 +203,7 @@ static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)		\
 
 CFQ_CFQQ_FNS(on_rr);
 CFQ_CFQQ_FNS(wait_request);
+CFQ_CFQQ_FNS(must_dispatch);
 CFQ_CFQQ_FNS(must_alloc);
 CFQ_CFQQ_FNS(must_alloc_slice);
 CFQ_CFQQ_FNS(fifo_expire);
@@ -774,6 +776,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
                 cfqq->slice_dispatch = 0;
 
                 cfq_clear_cfqq_wait_request(cfqq);
+                cfq_clear_cfqq_must_dispatch(cfqq);
                 cfq_clear_cfqq_must_alloc_slice(cfqq);
                 cfq_clear_cfqq_fifo_expire(cfqq);
                 cfq_mark_cfqq_slice_new(cfqq);
@@ -1009,7 +1012,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
         /*
          * The active queue has run out of time, expire it and select new.
          */
-        if (cfq_slice_used(cfqq))
+        if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
                 goto expire;
 
         /*
@@ -1173,6 +1176,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
          */
         cfq_dispatch_request(cfqd, cfqq);
         cfqq->slice_dispatch++;
+        cfq_clear_cfqq_must_dispatch(cfqq);
 
         /*
          * expire an async queue immediately if it has used up its slice. idle
@@ -1898,14 +1902,13 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 
         if (cfqq == cfqd->active_queue) {
                 /*
-                 * if we are waiting for a request for this queue, let it rip
-                 * immediately and flag that we must not expire this queue
-                 * just now
+                 * 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.
                  */
-                if (cfq_cfqq_wait_request(cfqq)) {
-                        del_timer(&cfqd->idle_slice_timer);
-                        blk_start_queueing(cfqd->queue);
-                }
+                if (cfq_cfqq_wait_request(cfqq))
+                        cfq_mark_cfqq_must_dispatch(cfqq);
         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
                 /*
                  * not the active queue - expire current slice if it is
@@ -2175,6 +2178,12 @@ static void cfq_idle_slice_timer(unsigned long data)
                 timed_out = 0;
 
                 /*
+                 * We saw a request before the queue expired, let it through
+                 */
+                if (cfq_cfqq_must_dispatch(cfqq))
+                        goto out_kick;
+
+                /*
                  * expired
                  */
                 if (cfq_slice_used(cfqq))