[RFC] [PATCH 4/8] cfq-iosched: Get rid of st->active

[Gui Jianfeng]

When a cfq group is running, it won't be dequeued from service tree, so
there's no need to store the active one in st->active. Just gid rid of it.

Signed-off-by: Gui Jianfeng <guijianfeng@xxxxxxxxxxxxxx>
---
 block/cfq-iosched.c |   15 +--------------
 1 files changed, 1 insertions(+), 14 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ef88931..ad577b5 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -88,7 +88,6 @@ struct cfq_rb_root {
 	unsigned count;
 	unsigned total_weight;
 	u64 min_vdisktime;
-	struct rb_node *active;
 };
 #define CFQ_RB_ROOT	(struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
 			.count = 0, .min_vdisktime = 0, }
@@ -599,11 +598,6 @@ static void update_min_vdisktime(struct cfq_rb_root *st)
 	u64 vdisktime = st->min_vdisktime;
 	struct io_sched_entity *entity;
 
-	if (st->active) {
-		entity = rb_entry_entity(st->active);
-		vdisktime = entity->vdisktime;
-	}
-
 	if (st->left) {
 		entity = rb_entry_entity(st->left);
 		vdisktime = min_vdisktime(vdisktime, entity->vdisktime);
@@ -925,9 +919,6 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
 	struct cfq_rb_root *st = &cfqd->grp_service_tree;
 	struct io_sched_entity *group_entity = &cfqg->group_entity;
 
-	if (st->active == &group_entity->rb_node)
-		st->active = NULL;
-
 	BUG_ON(cfqg->nr_cfqq < 1);
 	cfqg->nr_cfqq--;
 
@@ -1130,7 +1121,7 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
 	if (!atomic_dec_and_test(&cfqg->ref))
 		return;
 	for_each_cfqg_st(cfqg, i, j, st)
-		BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
+		BUG_ON(!RB_EMPTY_ROOT(&st->rb));
 	kfree(cfqg);
 }
 
@@ -1773,9 +1764,6 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	if (cfqq == cfqd->active_queue)
 		cfqd->active_queue = NULL;
 
-	if (&cfqq->cfqg->group_entity.rb_node == cfqd->grp_service_tree.active)
-		cfqd->grp_service_tree.active = NULL;
-
 	if (cfqd->active_cic) {
 		put_io_context(cfqd->active_cic->ioc);
 		cfqd->active_cic = NULL;
@@ -2305,7 +2293,6 @@ static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
 	group_entity = cfq_rb_first_entity(st);
 	cfqg = cfqg_of_entity(group_entity);
 	BUG_ON(!cfqg);
-	st->active = &group_entity->rb_node;
 	update_min_vdisktime(st);
 	return cfqg;
 }
-- 
1.6.5.2





-- 
Regards
Gui Jianfeng
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