cfq-iosched: Add comments on update timing of weight
Explain that weight has to be updated on activation.
This complements previous fix e15693ef18e1 ("cfq-iosched: Fix wrong
children_weight calculation").
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d749463..3f31cf9 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1272,6 +1272,9 @@
rb_insert_color(&cfqg->rb_node, &st->rb);
}
+/*
+ * This has to be called only on activation of cfqg
+ */
static void
cfq_update_group_weight(struct cfq_group *cfqg)
{
@@ -1303,6 +1306,11 @@
/* add to the service tree */
BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+ /*
+ * Update leaf_weight. We cannot update weight at this point
+ * because cfqg might already have been activated and is
+ * contributing its current weight to the parent's child_weight.
+ */
cfq_update_group_leaf_weight(cfqg);
__cfq_group_service_tree_add(st, cfqg);