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-rw-r--r--block/bfq-wf2q.c39
1 files changed, 34 insertions, 5 deletions
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 8726ede19eef..5ec05cd42b80 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -694,10 +694,28 @@ struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity)
return sched_data->service_tree + idx;
}
-
+/*
+ * Update weight and priority of entity. If update_class_too is true,
+ * then update the ioprio_class of entity too.
+ *
+ * The reason why the update of ioprio_class is controlled through the
+ * last parameter is as follows. Changing the ioprio class of an
+ * entity implies changing the destination service trees for that
+ * entity. If such a change occurred when the entity is already on one
+ * of the service trees for its previous class, then the state of the
+ * entity would become more complex: none of the new possible service
+ * trees for the entity, according to bfq_entity_service_tree(), would
+ * match any of the possible service trees on which the entity
+ * is. Complex operations involving these trees, such as entity
+ * activations and deactivations, should take into account this
+ * additional complexity. To avoid this issue, this function is
+ * invoked with update_class_too unset in the points in the code where
+ * entity may happen to be on some tree.
+ */
struct bfq_service_tree *
__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
- struct bfq_entity *entity)
+ struct bfq_entity *entity,
+ bool update_class_too)
{
struct bfq_service_tree *new_st = old_st;
@@ -739,9 +757,15 @@ __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
bfq_weight_to_ioprio(entity->orig_weight);
}
- if (bfqq)
+ if (bfqq && update_class_too)
bfqq->ioprio_class = bfqq->new_ioprio_class;
- entity->prio_changed = 0;
+
+ /*
+ * Reset prio_changed only if the ioprio_class change
+ * is not pending any longer.
+ */
+ if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class)
+ entity->prio_changed = 0;
/*
* NOTE: here we may be changing the weight too early,
@@ -867,7 +891,12 @@ static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
- st = __bfq_entity_update_weight_prio(st, entity);
+ /*
+ * When this function is invoked, entity is not in any service
+ * tree, then it is safe to invoke next function with the last
+ * parameter set (see the comments on the function).
+ */
+ st = __bfq_entity_update_weight_prio(st, entity, true);
bfq_calc_finish(entity, entity->budget);
/*