Re: [PATCH] cfq-iosched: Reduce linked group count upon group destruction

[Jens Axboe <jaxboe@fusionio.com>]

On 2011-08-01 20:47, Vivek Goyal wrote:
> CFQ 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.

Thanks Vivek, applied.

-- 
Jens Axboe