mm: memcontrol: export root_mem_cgroup

A later patch will need this symbol in files other than memcontrol.c, so
export it now and replace mem_cgroup_root_css at the same time.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0bc140d..44ed2de 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -76,9 +76,9 @@
 struct cgroup_subsys memory_cgrp_subsys __read_mostly;
 EXPORT_SYMBOL(memory_cgrp_subsys);
 
+struct mem_cgroup *root_mem_cgroup __read_mostly;
+
 #define MEM_CGROUP_RECLAIM_RETRIES	5
-static struct mem_cgroup *root_mem_cgroup __read_mostly;
-struct cgroup_subsys_state *mem_cgroup_root_css __read_mostly;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
@@ -4241,7 +4241,6 @@
 	/* root ? */
 	if (parent_css == NULL) {
 		root_mem_cgroup = memcg;
-		mem_cgroup_root_css = &memcg->css;
 		page_counter_init(&memcg->memory, NULL);
 		memcg->high = PAGE_COUNTER_MAX;
 		memcg->soft_limit = PAGE_COUNTER_MAX;