memcg: simplify and inline __mem_cgroup_from_kmem

Before the previous patch ("memcg: unify slab and other kmem pages
charging"), __mem_cgroup_from_kmem had to handle two types of kmem - slab
pages and pages allocated with alloc_kmem_pages - memcg in the page
struct.  Now we can unify it.  Since after it, this function becomes tiny
we can fold it into mem_cgroup_from_kmem.

[hughd@google.com: move mem_cgroup_from_kmem into list_lru.c]
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 10 insertions, 18 deletions

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 28237476b055..afc71ea9a381 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -63,6 +63,16 @@ list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
         return &nlru->lru;
 }
 
+static __always_inline struct mem_cgroup *mem_cgroup_from_kmem(void *ptr)
+{
+        struct page *page;
+
+        if (!memcg_kmem_enabled())
+                return NULL;
+        page = virt_to_head_page(ptr);
+        return page->mem_cgroup;
+}
+
 static inline struct list_lru_one *
 list_lru_from_kmem(struct list_lru_node *nlru, void *ptr)
 {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9575cff544fa..c0111cb667b5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2430,24 +2430,6 @@ void __memcg_kmem_uncharge(struct page *page, int order)
         page->mem_cgroup = NULL;
         css_put_many(&memcg->css, nr_pages);
 }
-
-struct mem_cgroup *__mem_cgroup_from_kmem(void *ptr)
-{
-        struct mem_cgroup *memcg = NULL;
-        struct kmem_cache *cachep;
-        struct page *page;
-
-        page = virt_to_head_page(ptr);
-        if (PageSlab(page)) {
-                cachep = page->slab_cache;
-                if (!is_root_cache(cachep))
-                        memcg = cachep->memcg_params.memcg;
-        } else
-                /* page allocated by alloc_kmem_pages */
-                memcg = page->mem_cgroup;
-
-        return memcg;
-}
 #endif /* CONFIG_MEMCG_KMEM */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE