memcg: zap kmem_account_flags

The only such flag is KMEM_ACCOUNTED_ACTIVE, but it's set iff
mem_cgroup->kmemcg_id is initialized, so we can check kmemcg_id instead of
having a separate flags field.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 21 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5a27e224d561..bb8c237026cc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -296,7 +296,6 @@ struct mem_cgroup {
          * Should the accounting and control be hierarchical, per subtree?
          */
         bool use_hierarchy;
-        unsigned long kmem_account_flags; /* See KMEM_ACCOUNTED_*, below */
 
         bool            oom_lock;
         atomic_t        under_oom;
@@ -366,22 +365,11 @@ struct mem_cgroup {
         /* WARNING: nodeinfo must be the last member here */
 };
 
-/* internal only representation about the status of kmem accounting. */
-enum {
-        KMEM_ACCOUNTED_ACTIVE, /* accounted by this cgroup itself */
-};
-
 #ifdef CONFIG_MEMCG_KMEM
-static inline void memcg_kmem_set_active(struct mem_cgroup *memcg)
-{
-        set_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
-}
-
 static bool memcg_kmem_is_active(struct mem_cgroup *memcg)
 {
-        return test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
+        return memcg->kmemcg_id >= 0;
 }
-
 #endif
 
 /* Stuffs for move charges at task migration. */
@@ -3564,23 +3552,21 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg,
                 goto out;
         }
 
-        memcg->kmemcg_id = memcg_id;
-        INIT_LIST_HEAD(&memcg->memcg_slab_caches);
-
         /*
-         * We couldn't have accounted to this cgroup, because it hasn't got the
-         * active bit set yet, so this should succeed.
+         * We couldn't have accounted to this cgroup, because it hasn't got
+         * activated yet, so this should succeed.
          */
         err = page_counter_limit(&memcg->kmem, nr_pages);
         VM_BUG_ON(err);
 
         static_key_slow_inc(&memcg_kmem_enabled_key);
         /*
-         * Setting the active bit after enabling static branching will
+         * A memory cgroup is considered kmem-active 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_kmem_set_active(memcg);
+        memcg->kmemcg_id = memcg_id;
 out:
         return err;
 }
@@ -4252,7 +4238,6 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
         int ret;
 
-        memcg->kmemcg_id = -1;
         ret = memcg_propagate_kmem(memcg);
         if (ret)
                 return ret;
@@ -4786,6 +4771,10 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
         vmpressure_init(&memcg->vmpressure);
         INIT_LIST_HEAD(&memcg->event_list);
         spin_lock_init(&memcg->event_list_lock);
+#ifdef CONFIG_MEMCG_KMEM
+        memcg->kmemcg_id = -1;
+        INIT_LIST_HEAD(&memcg->memcg_slab_caches);
+#endif
 
         return &memcg->css;