From a5395b83b78f62ccf5e3af854aacd025c2a6e7b5 Mon Sep 17 00:00:00 2001 From: Vivek Goyal <vgoyal@redhat.com> Date: Tue, 2 Aug 2011 09:24:09 +0200 Subject: [PATCH] cfq-iosched: Reduce linked group count upon group destruction FQ keeps track of number of groups which are linked on blkcg->blkg_list. This is useful to avoid races between queue exit and cgroup exit code paths. So if at the request queue exit time linked group count is not zero, that means there are some group out there which is yet to be deleted under rcu read period and queue exit code should wait for on rcu period. In my previous patch I forgot to decrease the number of group count. So in current form, we nr_blkcg_linked_grps is always non-zero and we will always wait one rcu period (if BLK_CGROUP=y). The side effect of this is that it can increase boot time. I am surprised, nobody complained so far. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> --- block/cfq-iosched.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 1f96ad6254f1..650834537606 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1209,6 +1209,9 @@ static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) hlist_del_init(&cfqg->cfqd_node); + BUG_ON(cfqd->nr_blkcg_linked_grps <= 0); + cfqd->nr_blkcg_linked_grps--; + /* * Put the reference taken at the time of creation so that when all * queues are gone, group can be destroyed.