From 7b5af5cffce569298b1d03af1ddf1dc43570ab42 Mon Sep 17 00:00:00 2001 From: Toshiaki Makita Date: Thu, 28 Aug 2014 17:14:58 +0900 Subject: [PATCH] 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 Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index d7494637c5db..3f31cf9508e6 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1272,6 +1272,9 @@ __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) 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 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) /* 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);