blk-throttle: clean up blkg_policy_data alloc/init/exit/free methods

With the recent addition of alloc and free methods, things became
messier.  This patch reorganizes them according to the followings.

* ->pd_alloc_fn()

  Responsible for allocation and static initializations - the ones
  which can be done independent of where the pd might be attached.

* ->pd_init_fn()

  Initializations which require the knowledge of where the pd is
  attached.

* ->pd_free_fn()

  The counter part of pd_alloc_fn().  Static de-init and freeing.

This leaves ->pd_exit_fn() without any users.  Removed.

While at it, collapse an one liner function throtl_pd_exit(), which
has only one user, into its user.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-cgroup.c

@@ -402,15 +402,6 @@ static void blkg_destroy_all(struct request_queue *q)
 void __blkg_release_rcu(struct rcu_head *rcu_head)
 {
 	struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
-	int i;
-
-	/* tell policies that this one is being freed */
-	for (i = 0; i < BLKCG_MAX_POLS; i++) {
-		struct blkcg_policy *pol = blkcg_policy[i];
-
-		if (blkg->pd[i] && pol->pd_exit_fn)
-			pol->pd_exit_fn(blkg);
-	}
 
 	/* release the blkcg and parent blkg refs this blkg has been holding */
 	css_put(&blkg->blkcg->css);
@@ -1127,8 +1118,6 @@ void blkcg_deactivate_policy(struct request_queue *q,
 
 		if (pol->pd_offline_fn)
 			pol->pd_offline_fn(blkg);
-		if (pol->pd_exit_fn)
-			pol->pd_exit_fn(blkg);
 
 		if (blkg->pd[pol->plid]) {
 			pol->pd_free_fn(blkg->pd[pol->plid]);

block/blk-throttle.c

@@ -330,26 +330,19 @@ static struct bio *throtl_pop_queued(struct list_head *queued,
 }
 
 /* init a service_queue, assumes the caller zeroed it */
-static void throtl_service_queue_init(struct throtl_service_queue *sq,
-				      struct throtl_service_queue *parent_sq)
+static void throtl_service_queue_init(struct throtl_service_queue *sq)
 {
 	INIT_LIST_HEAD(&sq->queued[0]);
 	INIT_LIST_HEAD(&sq->queued[1]);
 	sq->pending_tree = RB_ROOT;
-	sq->parent_sq = parent_sq;
 	setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
 		    (unsigned long)sq);
 }
 
-static void throtl_service_queue_exit(struct throtl_service_queue *sq)
-{
-	del_timer_sync(&sq->pending_timer);
-}
-
 static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 {
 	struct throtl_grp *tg;
-	int cpu;
+	int rw, cpu;
 
 	tg = kzalloc_node(sizeof(*tg), gfp, node);
 	if (!tg)
@@ -361,6 +354,19 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 		return NULL;
 	}
 
+	throtl_service_queue_init(&tg->service_queue);
+
+	for (rw = READ; rw <= WRITE; rw++) {
+		throtl_qnode_init(&tg->qnode_on_self[rw], tg);
+		throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
+	}
+
+	RB_CLEAR_NODE(&tg->rb_node);
+	tg->bps[READ] = -1;
+	tg->bps[WRITE] = -1;
+	tg->iops[READ] = -1;
+	tg->iops[WRITE] = -1;
+
 	for_each_possible_cpu(cpu) {
 		struct tg_stats_cpu *stats_cpu = per_cpu_ptr(tg->stats_cpu, cpu);
 
@@ -375,8 +381,7 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
 {
 	struct throtl_grp *tg = blkg_to_tg(blkg);
 	struct throtl_data *td = blkg->q->td;
-	struct throtl_service_queue *parent_sq;
-	int rw;
+	struct throtl_service_queue *sq = &tg->service_queue;
 
 	/*
 	 * If on the default hierarchy, we switch to properly hierarchical
@@ -391,25 +396,10 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
 	 * Limits of a group don't interact with limits of other groups
 	 * regardless of the position of the group in the hierarchy.
 	 */
-	parent_sq = &td->service_queue;
-
+	sq->parent_sq = &td->service_queue;
 	if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent)
-		parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
-
-	throtl_service_queue_init(&tg->service_queue, parent_sq);
-
-	for (rw = READ; rw <= WRITE; rw++) {
-		throtl_qnode_init(&tg->qnode_on_self[rw], tg);
-		throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
-	}
-
-	RB_CLEAR_NODE(&tg->rb_node);
+		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
 	tg->td = td;
-
-	tg->bps[READ] = -1;
-	tg->bps[WRITE] = -1;
-	tg->iops[READ] = -1;
-	tg->iops[WRITE] = -1;
 }
 
 /*
@@ -436,17 +426,11 @@ static void throtl_pd_online(struct blkcg_gq *blkg)
 	tg_update_has_rules(blkg_to_tg(blkg));
 }
 
-static void throtl_pd_exit(struct blkcg_gq *blkg)
-{
-	struct throtl_grp *tg = blkg_to_tg(blkg);
-
-	throtl_service_queue_exit(&tg->service_queue);
-}
-
 static void throtl_pd_free(struct blkg_policy_data *pd)
 {
 	struct throtl_grp *tg = pd_to_tg(pd);
 
+	del_timer_sync(&tg->service_queue.pending_timer);
 	free_percpu(tg->stats_cpu);
 	kfree(tg);
 }
@@ -1421,7 +1405,6 @@ static struct blkcg_policy blkcg_policy_throtl = {
 	.pd_alloc_fn		= throtl_pd_alloc,
 	.pd_init_fn		= throtl_pd_init,
 	.pd_online_fn		= throtl_pd_online,
-	.pd_exit_fn		= throtl_pd_exit,
 	.pd_free_fn		= throtl_pd_free,
 	.pd_reset_stats_fn	= throtl_pd_reset_stats,
 };
@@ -1616,7 +1599,7 @@ int blk_throtl_init(struct request_queue *q)
 		return -ENOMEM;
 
 	INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
-	throtl_service_queue_init(&td->service_queue, NULL);
+	throtl_service_queue_init(&td->service_queue);
 
 	q->td = td;
 	td->queue = q;

block/cfq-iosched.c

@@ -1584,7 +1584,17 @@ static void cfq_cpd_init(const struct blkcg *blkcg)
 
 static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)
 {
-	return kzalloc_node(sizeof(struct cfq_group), gfp, node);
+	struct cfq_group *cfqg;
+
+	cfqg = kzalloc_node(sizeof(*cfqg), gfp, node);
+	if (!cfqg)
+		return NULL;
+
+	cfq_init_cfqg_base(cfqg);
+	cfqg_stats_init(&cfqg->stats);
+	cfqg_stats_init(&cfqg->dead_stats);
+
+	return &cfqg->pd;
 }
 
 static void cfq_pd_init(struct blkcg_gq *blkg)
@@ -1592,11 +1602,8 @@ static void cfq_pd_init(struct blkcg_gq *blkg)
 	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
 	struct cfq_group_data *cgd = blkcg_to_cfqgd(blkg->blkcg);
 
-	cfq_init_cfqg_base(cfqg);
 	cfqg->weight = cgd->weight;
 	cfqg->leaf_weight = cgd->leaf_weight;
-	cfqg_stats_init(&cfqg->stats);
-	cfqg_stats_init(&cfqg->dead_stats);
 }
 
 static void cfq_pd_offline(struct blkcg_gq *blkg)

include/linux/blk-cgroup.h

@@ -128,7 +128,6 @@ typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp, int node);
 typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);
 typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
 typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);
-typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
 typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
 
@@ -145,7 +144,6 @@ struct blkcg_policy {
 	blkcg_pol_init_pd_fn		*pd_init_fn;
 	blkcg_pol_online_pd_fn		*pd_online_fn;
 	blkcg_pol_offline_pd_fn		*pd_offline_fn;
-	blkcg_pol_exit_pd_fn		*pd_exit_fn;
 	blkcg_pol_free_pd_fn		*pd_free_fn;
 	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;
 };