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SubjectRe: [PATCH 11/12] blkcg: kill blkio_policy_node
Hello,

On Thu, Jan 19, 2012 at 03:32:25PM -0500, Vivek Goyal wrote:
> On Wed, Jan 18, 2012 at 05:11:29PM -0800, Tejun Heo wrote:
>
> [..]
> > @@ -1413,14 +1110,10 @@ static int blkio_weight_write(struct blkio_cgroup *blkcg, u64 val)
> > spin_lock_irq(&blkcg->lock);
> > blkcg->weight = (unsigned int)val;
> >
> > - hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
> > - pn = blkio_policy_search_node(blkcg, blkg->dev,
> > - BLKIO_POLICY_PROP, BLKIO_PROP_weight_device);
> > - if (pn)
> > - continue;
> > + hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
> > + if (blkg->plid == plid && !blkg->conf.weight)
> > + blkio_update_group_weight(blkg, blkcg->weight);
>
> Tejun,
>
> Why do we check for blkg->conf.weight=0 here. Even if a group already has
> weight and if user has changed the cgroup weight later, that update should
> be propogated to all the groups on all the queues.

Maybe I misread the code but if explicit per-device config exists,
cgroup-wide writes are ignored, no? The original code searches for
matching pn and if it exists, continues without updating.

> Where do we assign default cgroup weight to a blkg upon creation? May be at
> group create time, we just need to copy blkcg->weight to blkg.conf.weight.

We don't. blk->conf.weight is set only on explicit per-device
configuration. It's gonna be removed eventually after config
definition and handling are moved into policies.

Thanks.

--
tejun


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