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[sfrench/cifs-2.6.git] / block / cfq-iosched.c

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index a0102a507dae4caa41d1c36863af1aa34527dd30..a4809de6fea656a4ac6091f6c61c38f536a4f766 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -177,13 +177,12 @@ 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_must_dispatch,    /* must dispatch, even if expired */
        CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
        CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
        CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
-       CFQ_CFQQ_FLAG_queue_new,        /* queue never been serviced */
        CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
        CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
 };
@@ -204,13 +203,12 @@ 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(must_dispatch);
 CFQ_CFQQ_FNS(fifo_expire);
 CFQ_CFQQ_FNS(idle_window);
 CFQ_CFQQ_FNS(prio_changed);
-CFQ_CFQQ_FNS(queue_new);
 CFQ_CFQQ_FNS(slice_new);
 CFQ_CFQQ_FNS(sync);
 #undef CFQ_CFQQ_FNS
@@ -777,12 +775,11 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
                cfqq->slice_end = 0;
                cfqq->slice_dispatch = 0;
 
-               cfq_clear_cfqq_must_dispatch(cfqq);
                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);
-               cfq_clear_cfqq_queue_new(cfqq);
 
                del_timer(&cfqd->idle_slice_timer);
        }
@@ -802,7 +799,6 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
        if (cfq_cfqq_wait_request(cfqq))
                del_timer(&cfqd->idle_slice_timer);
 
-       cfq_clear_cfqq_must_dispatch(cfqq);
        cfq_clear_cfqq_wait_request(cfqq);
 
        /*
@@ -931,7 +927,6 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
            (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
                return;
 
-       cfq_mark_cfqq_must_dispatch(cfqq);
        cfq_mark_cfqq_wait_request(cfqq);
 
        /*
@@ -1017,7 +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;
 
        /*
@@ -1181,6 +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
@@ -1520,7 +1516,6 @@ retry:
                cfqq->cfqd = cfqd;
 
                cfq_mark_cfqq_prio_changed(cfqq);
-               cfq_mark_cfqq_queue_new(cfqq);
 
                cfq_init_prio_data(cfqq, ioc);
 
@@ -1907,15 +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)) {
+               if (cfq_cfqq_wait_request(cfqq))
                        cfq_mark_cfqq_must_dispatch(cfqq);
-                       del_timer(&cfqd->idle_slice_timer);
-                       blk_start_queueing(cfqd->queue);
-               }
        } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
                /*
                 * not the active queue - expire current slice if it is
@@ -1924,7 +1917,6 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 * this new queue is RT and the current one is BE
                 */
                cfq_preempt_queue(cfqd, cfqq);
-               cfq_mark_cfqq_must_dispatch(cfqq);
                blk_start_queueing(cfqd->queue);
        }
 }
@@ -2185,6 +2177,12 @@ static void cfq_idle_slice_timer(unsigned long data)
        if (cfqq) {
                timed_out = 0;
 
+               /*
+                * We saw a request before the queue expired, let it through
+                */
+               if (cfq_cfqq_must_dispatch(cfqq))
+                       goto out_kick;
+
                /*
                 * expired
                 */
@@ -2201,10 +2199,8 @@ static void cfq_idle_slice_timer(unsigned long data)
                /*
                 * not expired and it has a request pending, let it dispatch
                 */
-               if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
-                       cfq_mark_cfqq_must_dispatch(cfqq);
+               if (!RB_EMPTY_ROOT(&cfqq->sort_list))
                        goto out_kick;
-               }
        }
 expire:
        cfq_slice_expired(cfqd, timed_out);