cfq-iosched: get rid of ->cur_rr and ->cfq_list

It's only used for preemption now that the IDLE and RT queues also
use the rbtree. If we pass an 'add_front' variable to
cfq_service_tree_add(), we can set ->rb_key to 0 to force insertion
at the front of the tree.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 32 insertions, 55 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4a0397022f5b..a8437042e28a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -45,9 +45,6 @@ static int cfq_slice_idle = HZ / 125;
  */
 #define CFQ_QHASH_SHIFT         6
 #define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
-#define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
-
-#define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
 
 #define RQ_CIC(rq)              ((struct cfq_io_context*)(rq)->elevator_private)
 #define RQ_CFQQ(rq)             ((rq)->elevator_private2)
@@ -91,7 +88,6 @@ struct cfq_data {
          * rr list of queues with requests and the count of them
          */
         struct cfq_rb_root service_tree;
-        struct list_head cur_rr;
         unsigned int busy_queues;
 
         /*
@@ -146,8 +142,6 @@ struct cfq_queue {
         struct hlist_node cfq_hash;
         /* hash key */
         unsigned int key;
-        /* member of the rr/busy/cur/idle cfqd list */
-        struct list_head cfq_list;
         /* service_tree member */
         struct rb_node rb_node;
         /* service_tree key */
@@ -452,16 +446,19 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
  * we will service the queues.
  */
 static void cfq_service_tree_add(struct cfq_data *cfqd,
-                                    struct cfq_queue *cfqq)
+                                    struct cfq_queue *cfqq, int add_front)
 {
         struct rb_node **p = &cfqd->service_tree.rb.rb_node;
         struct rb_node *parent = NULL;
         unsigned long rb_key;
         int left;
 
-        rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
-        rb_key += cfqq->slice_resid;
-        cfqq->slice_resid = 0;
+        if (!add_front) {
+                rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
+                rb_key += cfqq->slice_resid;
+                cfqq->slice_resid = 0;
+        } else
+                rb_key = 0;
 
         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
                 /*
@@ -516,13 +513,13 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
 /*
  * Update cfqq's position in the service tree.
  */
-static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
+static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         /*
          * Resorting requires the cfqq to be on the RR list already.
          */
         if (cfq_cfqq_on_rr(cfqq))
-                cfq_service_tree_add(cfqq->cfqd, cfqq);
+                cfq_service_tree_add(cfqd, cfqq, 0);
 }
 
 /*
@@ -536,7 +533,7 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         cfq_mark_cfqq_on_rr(cfqq);
         cfqd->busy_queues++;
 
-        cfq_resort_rr_list(cfqq, 0);
+        cfq_resort_rr_list(cfqd, cfqq);
 }
 
 /*
@@ -548,7 +545,6 @@ cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         BUG_ON(!cfq_cfqq_on_rr(cfqq));
         cfq_clear_cfqq_on_rr(cfqq);
-        list_del_init(&cfqq->cfq_list);
 
         if (!RB_EMPTY_NODE(&cfqq->rb_node))
                 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
@@ -771,7 +767,7 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         if (timed_out && !cfq_cfqq_slice_new(cfqq))
                 cfqq->slice_resid = cfqq->slice_end - jiffies;
 
-        cfq_resort_rr_list(cfqq, preempted);
+        cfq_resort_rr_list(cfqd, cfqq);
 
         if (cfqq == cfqd->active_queue)
                 cfqd->active_queue = NULL;
@@ -799,31 +795,28 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
  */
 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
-        struct cfq_queue *cfqq = NULL;
+        struct cfq_queue *cfqq;
+        struct rb_node *n;
 
-        if (!list_empty(&cfqd->cur_rr)) {
-                /*
-                 * if current list is non-empty, grab first entry.
-                 */
-                cfqq = list_entry_cfqq(cfqd->cur_rr.next);
-        } else if (!RB_EMPTY_ROOT(&cfqd->service_tree.rb)) {
-                struct rb_node *n = cfq_rb_first(&cfqd->service_tree);
+        if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
+                return NULL;
 
-                cfqq = rb_entry(n, struct cfq_queue, rb_node);
-                if (cfq_class_idle(cfqq)) {
-                        unsigned long end;
+        n = cfq_rb_first(&cfqd->service_tree);
+        cfqq = rb_entry(n, struct cfq_queue, rb_node);
 
-                        /*
-                         * if we have idle queues and no rt or be queues had
-                         * pending requests, either allow immediate service if
-                         * the grace period has passed or arm the idle grace
-                         * timer
-                         */
-                        end = cfqd->last_end_request + CFQ_IDLE_GRACE;
-                        if (time_before(jiffies, end)) {
-                                mod_timer(&cfqd->idle_class_timer, end);
-                                cfqq = NULL;
-                        }
+        if (cfq_class_idle(cfqq)) {
+                unsigned long end;
+
+                /*
+                 * if we have idle queues and no rt or be queues had
+                 * pending requests, either allow immediate service if
+                 * the grace period has passed or arm the idle grace
+                 * timer
+                 */
+                end = cfqd->last_end_request + CFQ_IDLE_GRACE;
+                if (time_before(jiffies, end)) {
+                        mod_timer(&cfqd->idle_class_timer, end);
+                        cfqq = NULL;
                 }
         }
 
@@ -1075,18 +1068,6 @@ static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
         return dispatched;
 }
 
-static int cfq_forced_dispatch_cfqqs(struct list_head *list)
-{
-        struct cfq_queue *cfqq, *next;
-        int dispatched;
-
-        dispatched = 0;
-        list_for_each_entry_safe(cfqq, next, list, cfq_list)
-                dispatched += __cfq_forced_dispatch_cfqq(cfqq);
-
-        return dispatched;
-}
-
 /*
  * Drain our current requests. Used for barriers and when switching
  * io schedulers on-the-fly.
@@ -1102,8 +1083,6 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
         }
 
-        dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
-
         cfq_slice_expired(cfqd, 0, 0);
 
         BUG_ON(cfqd->busy_queues);
@@ -1433,7 +1412,6 @@ retry:
                 memset(cfqq, 0, sizeof(*cfqq));
 
                 INIT_HLIST_NODE(&cfqq->cfq_hash);
-                INIT_LIST_HEAD(&cfqq->cfq_list);
                 RB_CLEAR_NODE(&cfqq->rb_node);
                 INIT_LIST_HEAD(&cfqq->fifo);
 
@@ -1712,8 +1690,8 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
          * so we know that it will be selected next.
          */
         BUG_ON(!cfq_cfqq_on_rr(cfqq));
-        list_del_init(&cfqq->cfq_list);
-        list_add(&cfqq->cfq_list, &cfqd->cur_rr);
+
+        cfq_service_tree_add(cfqd, cfqq, 1);
 
         cfqq->slice_end = 0;
         cfq_mark_cfqq_slice_new(cfqq);
@@ -2077,7 +2055,6 @@ static void *cfq_init_queue(request_queue_t *q)
         memset(cfqd, 0, sizeof(*cfqd));
 
         cfqd->service_tree = CFQ_RB_ROOT;
-        INIT_LIST_HEAD(&cfqd->cur_rr);
         INIT_LIST_HEAD(&cfqd->cic_list);
 
         cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);