1 files changed, 41 insertions, 98 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1f7127b03490d..53b7bd4c7000c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -79,6 +79,7 @@ static void blkg_free(struct blkcg_gq *blkg)
 
 	blkg_rwstat_exit(&blkg->stat_ios);
 	blkg_rwstat_exit(&blkg->stat_bytes);
+	percpu_ref_exit(&blkg->refcnt);
 	kfree(blkg);
 }
 
@@ -86,8 +87,6 @@ static void __blkg_release(struct rcu_head *rcu)
 {
 	struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
 
-	percpu_ref_exit(&blkg->refcnt);
-
 	/* release the blkcg and parent blkg refs this blkg has been holding */
 	css_put(&blkg->blkcg->css);
 	if (blkg->parent)
@@ -132,6 +131,9 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 	if (!blkg)
 		return NULL;
 
+	if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
+		goto err_free;
+
 	if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) ||
 	    blkg_rwstat_init(&blkg->stat_ios, gfp_mask))
 		goto err_free;
@@ -244,11 +246,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 		blkg_get(blkg->parent);
 	}
 
-	ret = percpu_ref_init(&blkg->refcnt, blkg_release, 0,
-			      GFP_NOWAIT | __GFP_NOWARN);
-	if (ret)
-		goto err_cancel_ref;
-
 	/* invoke per-policy init */
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
@@ -281,8 +278,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	blkg_put(blkg);
 	return ERR_PTR(ret);
 
-err_cancel_ref:
-	percpu_ref_exit(&blkg->refcnt);
 err_put_congested:
 	wb_congested_put(wb_congested);
 err_put_css:
@@ -549,7 +544,7 @@ EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
  * Print @rwstat to @sf for the device assocaited with @pd.
  */
 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
-			 const struct blkg_rwstat *rwstat)
+			 const struct blkg_rwstat_sample *rwstat)
 {
 	static const char *rwstr[] = {
 		[BLKG_RWSTAT_READ]	= "Read",
@@ -567,31 +562,17 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 
 	for (i = 0; i < BLKG_RWSTAT_NR; i++)
 		seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
-			   (unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
+			   rwstat->cnt[i]);
 
-	v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
-		atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]) +
-		atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_DISCARD]);
-	seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
+	v = rwstat->cnt[BLKG_RWSTAT_READ] +
+		rwstat->cnt[BLKG_RWSTAT_WRITE] +
+		rwstat->cnt[BLKG_RWSTAT_DISCARD];
+	seq_printf(sf, "%s Total %llu\n", dname, v);
 	return v;
 }
 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
 
 /**
- * blkg_prfill_stat - prfill callback for blkg_stat
- * @sf: seq_file to print to
- * @pd: policy private data of interest
- * @off: offset to the blkg_stat in @pd
- *
- * prfill callback for printing a blkg_stat.
- */
-u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
-{
-	return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
-}
-EXPORT_SYMBOL_GPL(blkg_prfill_stat);
-
-/**
  * blkg_prfill_rwstat - prfill callback for blkg_rwstat
  * @sf: seq_file to print to
  * @pd: policy private data of interest
@@ -602,8 +583,9 @@ EXPORT_SYMBOL_GPL(blkg_prfill_stat);
 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 		       int off)
 {
-	struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
+	struct blkg_rwstat_sample rwstat = { };
 
+	blkg_rwstat_read((void *)pd + off, &rwstat);
 	return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
@@ -611,8 +593,9 @@ EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
 static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
 				    struct blkg_policy_data *pd, int off)
 {
-	struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
+	struct blkg_rwstat_sample rwstat = { };
 
+	blkg_rwstat_read((void *)pd->blkg + off, &rwstat);
 	return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 
@@ -654,8 +637,9 @@ static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
 					      struct blkg_policy_data *pd,
 					      int off)
 {
-	struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
-							      NULL, off);
+	struct blkg_rwstat_sample rwstat;
+
+	blkg_rwstat_recursive_sum(pd->blkg, NULL, off, &rwstat);
 	return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 
@@ -690,52 +674,11 @@ int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v)
 EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive);
 
 /**
- * blkg_stat_recursive_sum - collect hierarchical blkg_stat
- * @blkg: blkg of interest
- * @pol: blkcg_policy which contains the blkg_stat
- * @off: offset to the blkg_stat in blkg_policy_data or @blkg
- *
- * Collect the blkg_stat specified by @blkg, @pol and @off and all its
- * online descendants and their aux counts.  The caller must be holding the
- * queue lock for online tests.
- *
- * If @pol is NULL, blkg_stat is at @off bytes into @blkg; otherwise, it is
- * at @off bytes into @blkg's blkg_policy_data of the policy.
- */
-u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
-			    struct blkcg_policy *pol, int off)
-{
-	struct blkcg_gq *pos_blkg;
-	struct cgroup_subsys_state *pos_css;
-	u64 sum = 0;
-
-	lockdep_assert_held(&blkg->q->queue_lock);
-
-	rcu_read_lock();
-	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
-		struct blkg_stat *stat;
-
-		if (!pos_blkg->online)
-			continue;
-
-		if (pol)
-			stat = (void *)blkg_to_pd(pos_blkg, pol) + off;
-		else
-			stat = (void *)blkg + off;
-
-		sum += blkg_stat_read(stat) + atomic64_read(&stat->aux_cnt);
-	}
-	rcu_read_unlock();
-
-	return sum;
-}
-EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
-
-/**
  * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
  * @blkg: blkg of interest
  * @pol: blkcg_policy which contains the blkg_rwstat
  * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
+ * @sum: blkg_rwstat_sample structure containing the results
  *
  * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
  * online descendants and their aux counts.  The caller must be holding the
@@ -744,13 +687,12 @@ EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
  * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
  * is at @off bytes into @blkg's blkg_policy_data of the policy.
  */
-struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
-					     struct blkcg_policy *pol, int off)
+void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol,
+		int off, struct blkg_rwstat_sample *sum)
 {
 	struct blkcg_gq *pos_blkg;
 	struct cgroup_subsys_state *pos_css;
-	struct blkg_rwstat sum = { };
-	int i;
+	unsigned int i;
 
 	lockdep_assert_held(&blkg->q->queue_lock);
 
@@ -767,13 +709,9 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
 			rwstat = (void *)pos_blkg + off;
 
 		for (i = 0; i < BLKG_RWSTAT_NR; i++)
-			atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) +
-				percpu_counter_sum_positive(&rwstat->cpu_cnt[i]),
-				&sum.aux_cnt[i]);
+			sum->cnt[i] = blkg_rwstat_read_counter(rwstat, i);
 	}
 	rcu_read_unlock();
-
-	return sum;
 }
 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
 
@@ -939,7 +877,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
 		const char *dname;
 		char *buf;
-		struct blkg_rwstat rwstat;
+		struct blkg_rwstat_sample rwstat;
 		u64 rbytes, wbytes, rios, wios, dbytes, dios;
 		size_t size = seq_get_buf(sf, &buf), off = 0;
 		int i;
@@ -959,17 +897,17 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 
 		spin_lock_irq(&blkg->q->queue_lock);
 
-		rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
-					offsetof(struct blkcg_gq, stat_bytes));
-		rbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
-		wbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
-		dbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]);
+		blkg_rwstat_recursive_sum(blkg, NULL,
+				offsetof(struct blkcg_gq, stat_bytes), &rwstat);
+		rbytes = rwstat.cnt[BLKG_RWSTAT_READ];
+		wbytes = rwstat.cnt[BLKG_RWSTAT_WRITE];
+		dbytes = rwstat.cnt[BLKG_RWSTAT_DISCARD];
 
-		rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
-					offsetof(struct blkcg_gq, stat_ios));
-		rios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
-		wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
-		dios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]);
+		blkg_rwstat_recursive_sum(blkg, NULL,
+					offsetof(struct blkcg_gq, stat_ios), &rwstat);
+		rios = rwstat.cnt[BLKG_RWSTAT_READ];
+		wios = rwstat.cnt[BLKG_RWSTAT_WRITE];
+		dios = rwstat.cnt[BLKG_RWSTAT_DISCARD];
 
 		spin_unlock_irq(&blkg->q->queue_lock);
 
@@ -1006,8 +944,12 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 		}
 next:
 		if (has_stats) {
-			off += scnprintf(buf+off, size-off, "\n");
-			seq_commit(sf, off);
+			if (off < size - 1) {
+				off += scnprintf(buf+off, size-off, "\n");
+				seq_commit(sf, off);
+			} else {
+				seq_commit(sf, -1);
+			}
 		}
 	}
 
@@ -1391,7 +1333,8 @@ pd_prealloc:
 
 	spin_lock_irq(&q->queue_lock);
 
-	list_for_each_entry(blkg, &q->blkg_list, q_node) {
+	/* blkg_list is pushed at the head, reverse walk to init parents first */
+	list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
 		struct blkg_policy_data *pd;
 
 		if (blkg->pd[pol->plid])