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>

3 files changed, 28 insertions, 30 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 71dced17b16d..24b6bded13f8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2378,7 +2378,7 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
         struct page_counter *counter;
         int ret;
 
-        if (!memcg_kmem_is_active(memcg))
+        if (!memcg_kmem_online(memcg))
                 return 0;
 
         if (!page_counter_try_charge(&memcg->kmem, nr_pages, &counter))
@@ -2861,14 +2861,13 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
 }
 
 #ifdef CONFIG_MEMCG_KMEM
-static int memcg_activate_kmem(struct mem_cgroup *memcg)
+static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
         int err = 0;
         int memcg_id;
 
         BUG_ON(memcg->kmemcg_id >= 0);
-        BUG_ON(memcg->kmem_acct_activated);
-        BUG_ON(memcg->kmem_acct_active);
+        BUG_ON(memcg->kmem_state);
 
         /*
          * For simplicity, we won't allow this to be disabled.  It also can't
@@ -2898,14 +2897,13 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg)
 
         static_branch_inc(&memcg_kmem_enabled_key);
         /*
-         * A memory cgroup is considered kmem-active as soon as it gets
+         * A memory cgroup is considered kmem-online as soon as it gets
          * kmemcg_id. Setting the id after enabling static branching will
          * guarantee no one starts accounting before all call sites are
          * patched.
          */
         memcg->kmemcg_id = memcg_id;
-        memcg->kmem_acct_activated = true;
-        memcg->kmem_acct_active = true;
+        memcg->kmem_state = KMEM_ONLINE;
 out:
         return err;
 }
@@ -2917,8 +2915,8 @@ static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
 
         mutex_lock(&memcg_limit_mutex);
         /* Top-level cgroup doesn't propagate from root */
-        if (!memcg_kmem_is_active(memcg)) {
-                ret = memcg_activate_kmem(memcg);
+        if (!memcg_kmem_online(memcg)) {
+                ret = memcg_online_kmem(memcg);
                 if (ret)
                         goto out;
         }
@@ -2938,11 +2936,12 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
 
         mutex_lock(&memcg_limit_mutex);
         /*
-         * If the parent cgroup is not kmem-active now, it cannot be activated
-         * after this point, because it has at least one child already.
+         * If the parent cgroup is not kmem-online now, it cannot be
+         * onlined after this point, because it has at least one child
+         * already.
          */
-        if (memcg_kmem_is_active(parent))
-                ret = memcg_activate_kmem(memcg);
+        if (memcg_kmem_online(parent))
+                ret = memcg_online_kmem(memcg);
         mutex_unlock(&memcg_limit_mutex);
         return ret;
 }
@@ -3590,22 +3589,21 @@ static int memcg_init_kmem(struct mem_cgroup *memcg)
         return tcp_init_cgroup(memcg);
 }
 
-static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
+static void memcg_offline_kmem(struct mem_cgroup *memcg)
 {
         struct cgroup_subsys_state *css;
         struct mem_cgroup *parent, *child;
         int kmemcg_id;
 
-        if (!memcg->kmem_acct_active)
+        if (memcg->kmem_state != KMEM_ONLINE)
                 return;
-
         /*
-         * Clear the 'active' flag before clearing memcg_caches arrays entries.
-         * Since we take the slab_mutex in memcg_deactivate_kmem_caches(), it
-         * guarantees no cache will be created for this cgroup after we are
-         * done (see memcg_create_kmem_cache()).
+         * Clear the online state before clearing memcg_caches array
+         * entries. The slab_mutex in memcg_deactivate_kmem_caches()
+         * guarantees that no cache will be created for this cgroup
+         * after we are done (see memcg_create_kmem_cache()).
          */
-        memcg->kmem_acct_active = false;
+        memcg->kmem_state = KMEM_ALLOCATED;
 
         memcg_deactivate_kmem_caches(memcg);
 
@@ -3636,9 +3634,9 @@ static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
         memcg_free_cache_id(kmemcg_id);
 }
 
-static void memcg_destroy_kmem(struct mem_cgroup *memcg)
+static void memcg_free_kmem(struct mem_cgroup *memcg)
 {
-        if (memcg->kmem_acct_activated) {
+        if (memcg->kmem_state == KMEM_ALLOCATED) {
                 memcg_destroy_kmem_caches(memcg);
                 static_branch_dec(&memcg_kmem_enabled_key);
                 WARN_ON(page_counter_read(&memcg->kmem));
@@ -3651,11 +3649,11 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
         return 0;
 }
 
-static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
+static void memcg_offline_kmem(struct mem_cgroup *memcg)
 {
 }
 
-static void memcg_destroy_kmem(struct mem_cgroup *memcg)
+static void memcg_free_kmem(struct mem_cgroup *memcg)
 {
 }
 #endif
@@ -4308,7 +4306,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 
         vmpressure_cleanup(&memcg->vmpressure);
 
-        memcg_deactivate_kmem(memcg);
+        memcg_offline_kmem(memcg);
 
         wb_memcg_offline(memcg);
 }
@@ -4324,7 +4322,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
-        memcg_destroy_kmem(memcg);
+        memcg_free_kmem(memcg);
 #ifdef CONFIG_INET
         if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                 static_branch_dec(&memcg_sockets_enabled_key);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index e016178063e1..8c262e6dc33e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -503,10 +503,10 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
         mutex_lock(&slab_mutex);
 
         /*
-         * The memory cgroup could have been deactivated while the cache
+         * The memory cgroup could have been offlined while the cache
          * creation work was pending.
          */
-        if (!memcg_kmem_is_active(memcg))
+        if (!memcg_kmem_online(memcg))
                 goto out_unlock;
 
         idx = memcg_cache_id(memcg);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5ac86956ff9d..05dd182f04fd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -411,7 +411,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
         struct shrinker *shrinker;
         unsigned long freed = 0;
 
-        if (memcg && !memcg_kmem_is_active(memcg))
+        if (memcg && !memcg_kmem_online(memcg))
                 return 0;
 
         if (nr_scanned == 0)