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cfq-iosched: Add comments on update timing of weight

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Explain that weight has to be updated on activation.
This complements previous fix e15693ef18 ("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>
This commit is contained in:
Toshiaki Makita 2014-08-28 17:14:58 +09:00 committed by Jens Axboe
parent e15693ef18
commit 7b5af5cffc
1 changed files with 8 additions and 0 deletions
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8
block/cfq-iosched.c
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@ -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);