mm: memcontrol: give the kmem states more descriptive names

On any given memcg, the kmem accounting feature has three separate
states: not initialized, structures allocated, and actively accounting
slab memory.  These are represented through a combination of the
kmem_acct_activated and kmem_acct_active flags, which is confusing.

Convert to a kmem_state enum with the states NONE, ALLOCATED, and
ONLINE.  Then rename the functions to modify the state accordingly.
This follows the nomenclature of css object states more closely.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 189f04d..54dab4d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -152,6 +152,12 @@
 	struct mem_cgroup_threshold_ary *spare;
 };
 
+enum memcg_kmem_state {
+	KMEM_NONE,
+	KMEM_ALLOCATED,
+	KMEM_ONLINE,
+};
+
 /*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
@@ -233,8 +239,7 @@
 #if defined(CONFIG_MEMCG_KMEM)
         /* Index in the kmem_cache->memcg_params.memcg_caches array */
 	int kmemcg_id;
-	bool kmem_acct_activated;
-	bool kmem_acct_active;
+	enum memcg_kmem_state kmem_state;
 #endif
 
 	int last_scanned_node;
@@ -750,9 +755,9 @@
 	return static_branch_unlikely(&memcg_kmem_enabled_key);
 }
 
-static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
+static inline bool memcg_kmem_online(struct mem_cgroup *memcg)
 {
-	return memcg->kmem_acct_active;
+	return memcg->kmem_state == KMEM_ONLINE;
 }
 
 /*
@@ -850,7 +855,7 @@
 	return false;
 }
 
-static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
+static inline bool memcg_kmem_online(struct mem_cgroup *memcg)
 {
 	return false;
 }