cgroup: add cgroup->id

With the introduction of generic cgroup hierarchy iterators, css_id is
being phased out.  It was unnecessarily complex, id'ing the wrong
thing (cgroups need IDs, not CSSes) and has other oddities like not
being available at ->css_alloc().

This patch adds cgroup->id, which is a simple per-hierarchy
ida-allocated ID which is assigned before ->css_alloc() and released
after ->css_free().

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c798997e5011..82cf9e6fc77b 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -159,6 +159,8 @@ struct cgroup {
          */
         atomic_t count;
 
+        int id;                         /* ida allocated in-hierarchy ID */
+
         /*
          * We link our 'sibling' struct into our parent's 'children'.
          * Our children link their 'sibling' into our 'children'.