Re: [PATCH cgroup/for-3.12] cgroup: make css_for_each_descendant() and friends include the origin css in the iteration

[Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

> Previously, all css descendant iterators didn't include the origin
> (root of subtree) css in the iteration.  The reasons were maintaining
> consistency with css_for_each_child() and that at the time of
> introduction more use cases needed skipping the origin anyway;
> however, given that css_is_descendant() considers self to be a
> descendant, omitting the origin css has become more confusing and
> looking at the accumulated use cases rather clearly indicates that
> including origin would result in simpler code overall.
> 
> While this is a change which can easily lead to subtle bugs, cgroup
> API including the iterators has recently gone through major
> restructuring and no out-of-tree changes will be applicable without
> adjustments making this a relatively acceptable opportunity for this
> type of change.
> 
> The conversions are mostly straight-forward.  If the iteration block
> had explicit origin handling before or after, it's moved inside the
> iteration.  If not, if (pos == origin) continue; is added.  Some
> conversions add extra reference get/put around origin handling by
> consolidating origin handling and the rest.  While the extra ref
> operations aren't strictly necessary, this shouldn't cause any
> noticeable difference.
> 
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
> Cc: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> Cc: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
> Cc: Balbir Singh <bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Aristeu Rozanski <aris-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

I was wondering this would be better when I converted cgroup_cfts_commits()
to use this iterator.

Acked-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>