Commit 576682fa authored by Paolo Valente's avatar Paolo Valente Committed by Jens Axboe
Browse files

block, bfq: make reparent_leaf_entity actually work only on leaf entities 



bfq_reparent_leaf_entity() reparents the input leaf entity (a leaf
entity represents just a bfq_queue in an entity tree). Yet, the input
entity is guaranteed to always be a leaf entity only in two-level
entity trees. In this respect, because of the error fixed by
commit 14afc593 ("block, bfq: fix overwrite of bfq_group pointer
in bfq_find_set_group()"), all (wrongly collapsed) entity trees happened
to actually have only two levels. After the latter commit, this does not
hold any longer.

This commit fixes this problem by modifying
bfq_reparent_leaf_entity(), so that it searches an active leaf entity
down the path that stems from the input entity. Such a leaf entity is
guaranteed to exist when bfq_reparent_leaf_entity() is invoked.

Tested-by: default avatar <cki-project@redhat.com>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c8997736

block/bfq-cgroup.c

+31 −17
Original line number Diff line number Diff line
@@ -815,39 +815,53 @@ static void bfq_flush_idle_tree(struct bfq_service_tree *st) 
/**

 * bfq_reparent_leaf_entity - move leaf entity to the root_group.

 * @bfqd: the device data structure with the root group.

 * @entity: the entity to move.

 * @entity: the entity to move, if entity is a leaf; or the parent entity

 *	    of an active leaf entity to move, if entity is not a leaf.

 */

static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,

				     struct bfq_entity *entity)

				     struct bfq_entity *entity,

				     int ioprio_class)

{

	struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);

	struct bfq_queue *bfqq;

	struct bfq_entity *child_entity = entity;



	while (child_entity->my_sched_data) { /* leaf not reached yet */

		struct bfq_sched_data *child_sd = child_entity->my_sched_data;

		struct bfq_service_tree *child_st = child_sd->service_tree +

			ioprio_class;

		struct rb_root *child_active = &child_st->active;



		child_entity = bfq_entity_of(rb_first(child_active));



		if (!child_entity)

			child_entity = child_sd->in_service_entity;

	}



	bfqq = bfq_entity_to_bfqq(child_entity);

	bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);

}



/**

 * bfq_reparent_active_entities - move to the root group all active

 *                                entities.

 * bfq_reparent_active_queues - move to the root group all active queues.

 * @bfqd: the device data structure with the root group.

 * @bfqg: the group to move from.

 * @st: the service tree with the entities.

 * @st: the service tree to start the search from.

 */

static void bfq_reparent_active_entities(struct bfq_data *bfqd,

static void bfq_reparent_active_queues(struct bfq_data *bfqd,

				       struct bfq_group *bfqg,

					 struct bfq_service_tree *st)

				       struct bfq_service_tree *st,

				       int ioprio_class)

{

	struct rb_root *active = &st->active;

	struct bfq_entity *entity = NULL;



	if (!RB_EMPTY_ROOT(&st->active))

		entity = bfq_entity_of(rb_first(active));

	struct bfq_entity *entity;



	for (; entity ; entity = bfq_entity_of(rb_first(active)))

		bfq_reparent_leaf_entity(bfqd, entity);

	while ((entity = bfq_entity_of(rb_first(active))))

		bfq_reparent_leaf_entity(bfqd, entity, ioprio_class);



	if (bfqg->sched_data.in_service_entity)

		bfq_reparent_leaf_entity(bfqd,

			bfqg->sched_data.in_service_entity);

					 bfqg->sched_data.in_service_entity,

					 ioprio_class);

}



/**
@@ -898,7 +912,7 @@ static void bfq_pd_offline(struct blkg_policy_data *pd) 
		 * There is no need to put the sync queues, as the

		 * scheduler has taken no reference.

		 */

		bfq_reparent_active_entities(bfqd, bfqg, st);

		bfq_reparent_active_queues(bfqd, bfqg, st, i);

	}



	__bfq_deactivate_entity(entity, false);

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