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Commit 329a6781 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

block cfq: don't use atomic_t for cfq_group 



cfq_group->ref is used with queue_lock hold, the only exception is
cfq_set_request, which looks like a bug to me, so ref doesn't need
to be an atomic and atomic operation is slower.

Signed-off-by: default avatarShaohua Li <shaohua.li@intel.com>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 30d7b944

block/cfq-iosched.c

+12 −11
Original line number Diff line number Diff line
@@ -207,7 +207,7 @@ struct cfq_group { 
	struct blkio_group blkg;

#ifdef CONFIG_CFQ_GROUP_IOSCHED

	struct hlist_node cfqd_node;

	atomic_t ref;

	int ref;

#endif

	/* number of requests that are on the dispatch list or inside driver */

	int dispatched;
@@ -1014,7 +1014,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create) 
	 * elevator which will be dropped by either elevator exit

	 * or cgroup deletion path depending on who is exiting first.

	 */

	atomic_set(&cfqg->ref, 1);

	cfqg->ref = 1;



	/*

	 * Add group onto cgroup list. It might happen that bdi->dev is
@@ -1059,7 +1059,7 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) 


static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)

{

	atomic_inc(&cfqg->ref);

	cfqg->ref++;

	return cfqg;

}
@@ -1071,7 +1071,7 @@ static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) 


	cfqq->cfqg = cfqg;

	/* cfqq reference on cfqg */

	atomic_inc(&cfqq->cfqg->ref);

	cfqq->cfqg->ref++;

}



static void cfq_put_cfqg(struct cfq_group *cfqg)
@@ -1079,8 +1079,9 @@ static void cfq_put_cfqg(struct cfq_group *cfqg) 
	struct cfq_rb_root *st;

	int i, j;



	BUG_ON(atomic_read(&cfqg->ref) <= 0);

	if (!atomic_dec_and_test(&cfqg->ref))

	BUG_ON(cfqg->ref <= 0);

	cfqg->ref--;

	if (cfqg->ref)

		return;

	for_each_cfqg_st(cfqg, i, j, st)

		BUG_ON(!RB_EMPTY_ROOT(&st->rb));
@@ -1188,7 +1189,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
			cfq_group_service_tree_del(cfqd, cfqq->cfqg);

		cfqq->orig_cfqg = cfqq->cfqg;

		cfqq->cfqg = &cfqd->root_group;

		atomic_inc(&cfqd->root_group.ref);

		cfqd->root_group.ref++;

		group_changed = 1;

	} else if (!cfqd->cfq_group_isolation

		   && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
@@ -3681,12 +3682,12 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 


	cfqq->allocated[rw]++;

	cfqq->ref++;



	spin_unlock_irqrestore(q->queue_lock, flags);



	rq->elevator_private = cic;

	rq->elevator_private2 = cfqq;

	rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg);



	spin_unlock_irqrestore(q->queue_lock, flags);



	return 0;



queue_fail:
@@ -3884,7 +3885,7 @@ static void *cfq_init_queue(struct request_queue *q) 
	 * Take a reference to root group which we never drop. This is just

	 * to make sure that cfq_put_cfqg() does not try to kfree root group

	 */

	atomic_set(&cfqg->ref, 1);

	cfqg->ref = 1;

	rcu_read_lock();

	cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,

					(void *)cfqd, 0);