linux-kernel - [PATCH -next 05/11] block, bfq: count root group into 'num_groups_with_pending

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Date:   Sat, 5 Mar 2022 17:11:59 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <tj@...nel.org>, <axboe@...nel.dk>, <paolo.valente@...aro.org>,
        <jack@...e.cz>
CC:     <cgroups@...r.kernel.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <yukuai3@...wei.com>,
        <yi.zhang@...wei.com>
Subject: [PATCH -next 05/11] block, bfq: count root group into 'num_groups_with_pending_reqs'

Root group is not counted into 'num_groups_with_pending_reqs' because
'entity->parent' is set to NULL for child entities, thus
for_each_entity() can't access root group.

This patch set root_group's entity to 'entity->parent' for child
entities, this way root_group will be counted because for_each_entity()
can access root_group in bfq_activate_requeue_entity(),

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/bfq-cgroup.c  | 6 +++---
 block/bfq-iosched.h | 3 ++-
 block/bfq-wf2q.c    | 5 +++++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 420eda2589c0..6cd65b5e790d 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -436,7 +436,7 @@ void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
 		 */
 		bfqg_and_blkg_get(bfqg);
 	}
-	entity->parent = bfqg->my_entity; /* NULL for root group */
+	entity->parent = &bfqg->entity;
 	entity->sched_data = &bfqg->sched_data;
 }
 
@@ -581,7 +581,7 @@ static void bfq_group_set_parent(struct bfq_group *bfqg,
 	struct bfq_entity *entity;
 
 	entity = &bfqg->entity;
-	entity->parent = parent->my_entity;
+	entity->parent = &parent->entity;
 	entity->sched_data = &parent->sched_data;
 }
 
@@ -688,7 +688,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 	else if (bfqd->last_bfqq_created == bfqq)
 		bfqd->last_bfqq_created = NULL;
 
-	entity->parent = bfqg->my_entity;
+	entity->parent = &bfqg->entity;
 	entity->sched_data = &bfqg->sched_data;
 	/* pin down bfqg and its associated blkg  */
 	bfqg_and_blkg_get(bfqg);
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index ddd8eff5c272..4530ab8b42ac 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1024,13 +1024,14 @@ extern struct blkcg_policy blkcg_policy_bfq;
 /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
 
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
-/* stop at one of the child entities of the root group */
+/* stop at root group */
 #define for_each_entity(entity)	\
 	for (; entity ; entity = entity->parent)
 
 #define is_root_entity(entity) \
 	(entity->sched_data == NULL)
 
+/* stop at one of the child entities of the root group */
 #define for_each_entity_not_root(entity) \
 	for (; entity && !is_root_entity(entity); entity = entity->parent)
 
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 17f1d2c5b8dc..138a2950b841 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -1125,6 +1125,11 @@ static void bfq_activate_requeue_entity(struct bfq_entity *entity,
 {
 	for_each_entity(entity) {
 		bfq_update_groups_with_pending_reqs(entity);
+
+		/* root group is not in service tree */
+		if (is_root_entity(entity))
+			break;
+
 		__bfq_activate_requeue_entity(entity, non_blocking_wait_rq);
 
 		if (!bfq_update_next_in_service(entity->sched_data, entity,
-- 
2.31.1