[PATCH 5.4 001/168] block, bfq: get a ref to a group when adding it to a service tree

Greg Kroah-Hartman
2020-03-10T13:33:34Z

From: Paolo Valente <paolo.valente@linaro.org>

[ Upstream commit db37a34c563bf4692b36990ae89005c031385e52 ]

BFQ schedules generic entities, which may represent either bfq_queues
or groups of bfq_queues. When an entity is inserted into a service
tree, a reference must be taken, to make sure that the entity does not
disappear while still referred in the tree. Unfortunately, such a
reference is mistakenly taken only if the entity represents a
bfq_queue. This commit takes a reference also in case the entity
represents a group.

Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Chris Evich <cevich@redhat.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bfq-cgroup.c | 2 +-
block/bfq-iosched.h | 1 +
block/bfq-wf2q.c | 12 ++++++++++--
3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 86a607cf19a10..0999d56bc4d19 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -332,7 +332,7 @@ static void bfqg_put(struct bfq_group *bfqg)
kfree(bfqg);
}

-static void bfqg_and_blkg_get(struct bfq_group *bfqg)
+void bfqg_and_blkg_get(struct bfq_group *bfqg)
{
/* see comments in bfq_bic_update_cgroup for why refcounting bfqg */
bfqg_get(bfqg);
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 5d1a519640f6a..e0e4a413d43a5 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -978,6 +978,7 @@ struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node);
+void bfqg_and_blkg_get(struct bfq_group *bfqg);
void bfqg_and_blkg_put(struct bfq_group *bfqg);

#ifdef CONFIG_BFQ_GROUP_IOSCHED
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 05f0bf4a1144d..44079147e396e 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -536,7 +536,9 @@ static void bfq_get_entity(struct bfq_entity *entity)
bfqq->ref++;
bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
bfqq, bfqq->ref);
- }
+ } else
+ bfqg_and_blkg_get(container_of(entity, struct bfq_group,
+ entity));
}

/**
@@ -650,8 +652,14 @@ static void bfq_forget_entity(struct bfq_service_tree *st,

entity->on_st = false;
st->wsum -= entity->weight;
- if (bfqq && !is_in_service)
+ if (is_in_service)
+ return;
+
+ if (bfqq)
bfq_put_queue(bfqq);
+ else
+ bfqg_and_blkg_put(container_of(entity, struct bfq_group,
+ entity));
}

/**
--
2.20.1