blkcg: make blkcg_policy methods take a pointer to blkcg_policy_data

The newly added ->pd_alloc_fn() and ->pd_free_fn() deal with pd
(blkg_policy_data) while the older ones use blkg (blkcg_gq).  As using
blkg doesn't make sense for ->pd_alloc_fn() and after allocation pd
can always be mapped to blkg and given that these are policy-specific
methods, it makes sense to converge on pd.

This patch makes all methods deal with pd instead of blkg.  Most
conversions are trivial.  In blk-cgroup.c, a couple method invocation
sites now test whether pd exists instead of policy state for
consistency.  This shouldn't cause any behavioral differences.

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

@@ -242,7 +242,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 		struct blkcg_policy *pol = blkcg_policy[i];
 
 		if (blkg->pd[i] && pol->pd_init_fn)
-			pol->pd_init_fn(blkg);
+			pol->pd_init_fn(blkg->pd[i]);
 	}
 
 	/* insert */
@@ -256,7 +256,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 			struct blkcg_policy *pol = blkcg_policy[i];
 
 			if (blkg->pd[i] && pol->pd_online_fn)
-				pol->pd_online_fn(blkg);
+				pol->pd_online_fn(blkg->pd[i]);
 		}
 	}
 	blkg->online = true;
@@ -347,7 +347,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 		struct blkcg_policy *pol = blkcg_policy[i];
 
 		if (blkg->pd[i] && pol->pd_offline_fn)
-			pol->pd_offline_fn(blkg);
+			pol->pd_offline_fn(blkg->pd[i]);
 	}
 	blkg->online = false;
 
@@ -468,9 +468,8 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 		for (i = 0; i < BLKCG_MAX_POLS; i++) {
 			struct blkcg_policy *pol = blkcg_policy[i];
 
-			if (blkcg_policy_enabled(blkg->q, pol) &&
-			    pol->pd_reset_stats_fn)
-				pol->pd_reset_stats_fn(blkg);
+			if (blkg->pd[i] && pol->pd_reset_stats_fn)
+				pol->pd_reset_stats_fn(blkg->pd[i]);
 		}
 	}
 
@@ -1076,7 +1075,7 @@ pd_prealloc:
 		pd->blkg = blkg;
 		pd->plid = pol->plid;
 		if (pol->pd_init_fn)
-			pol->pd_init_fn(blkg);
+			pol->pd_init_fn(pd);
 	}
 
 	__set_bit(pol->plid, q->blkcg_pols);
@@ -1116,10 +1115,9 @@ void blkcg_deactivate_policy(struct request_queue *q,
 		/* grab blkcg lock too while removing @pd from @blkg */
 		spin_lock(&blkg->blkcg->lock);
 
-		if (pol->pd_offline_fn)
-			pol->pd_offline_fn(blkg);
-
 		if (blkg->pd[pol->plid]) {
+			if (pol->pd_offline_fn)
+				pol->pd_offline_fn(blkg->pd[pol->plid]);
 			pol->pd_free_fn(blkg->pd[pol->plid]);
 			blkg->pd[pol->plid] = NULL;
 		}

block/blk-throttle.c

@@ -377,9 +377,10 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
 	return &tg->pd;
 }
 
-static void throtl_pd_init(struct blkcg_gq *blkg)
+static void throtl_pd_init(struct blkg_policy_data *pd)
 {
-	struct throtl_grp *tg = blkg_to_tg(blkg);
+	struct throtl_grp *tg = pd_to_tg(pd);
+	struct blkcg_gq *blkg = tg_to_blkg(tg);
 	struct throtl_data *td = blkg->q->td;
 	struct throtl_service_queue *sq = &tg->service_queue;
 
@@ -417,13 +418,13 @@ static void tg_update_has_rules(struct throtl_grp *tg)
 				    (tg->bps[rw] != -1 || tg->iops[rw] != -1);
 }
 
-static void throtl_pd_online(struct blkcg_gq *blkg)
+static void throtl_pd_online(struct blkg_policy_data *pd)
 {
 	/*
 	 * We don't want new groups to escape the limits of its ancestors.
 	 * Update has_rules[] after a new group is brought online.
 	 */
-	tg_update_has_rules(blkg_to_tg(blkg));
+	tg_update_has_rules(pd_to_tg(pd));
 }
 
 static void throtl_pd_free(struct blkg_policy_data *pd)
@@ -435,9 +436,9 @@ static void throtl_pd_free(struct blkg_policy_data *pd)
 	kfree(tg);
 }
 
-static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
+static void throtl_pd_reset_stats(struct blkg_policy_data *pd)
 {
-	struct throtl_grp *tg = blkg_to_tg(blkg);
+	struct throtl_grp *tg = pd_to_tg(pd);
 	int cpu;
 
 	for_each_possible_cpu(cpu) {

block/cfq-iosched.c

@@ -1597,18 +1597,18 @@ static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)
 	return &cfqg->pd;
 }
 
-static void cfq_pd_init(struct blkcg_gq *blkg)
+static void cfq_pd_init(struct blkg_policy_data *pd)
 {
-	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
-	struct cfq_group_data *cgd = blkcg_to_cfqgd(blkg->blkcg);
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
+	struct cfq_group_data *cgd = blkcg_to_cfqgd(pd->blkg->blkcg);
 
 	cfqg->weight = cgd->weight;
 	cfqg->leaf_weight = cgd->leaf_weight;
 }
 
-static void cfq_pd_offline(struct blkcg_gq *blkg)
+static void cfq_pd_offline(struct blkg_policy_data *pd)
 {
-	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
 	int i;
 
 	for (i = 0; i < IOPRIO_BE_NR; i++) {
@@ -1661,9 +1661,9 @@ static struct blkg_rwstat cfqg_rwstat_pd_recursive_sum(struct blkg_policy_data *
 	return a;
 }
 
-static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
+static void cfq_pd_reset_stats(struct blkg_policy_data *pd)
 {
-	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
 
 	cfqg_stats_reset(&cfqg->stats);
 	cfqg_stats_reset(&cfqg->dead_stats);

include/linux/blk-cgroup.h

@@ -125,11 +125,11 @@ struct blkcg_gq {
 
 typedef void (blkcg_pol_init_cpd_fn)(const struct blkcg *blkcg);
 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_init_pd_fn)(struct blkg_policy_data *pd);
+typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
+typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
-typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
 
 struct blkcg_policy {
 	int				plid;