1 files changed, 41 insertions, 0 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 45085e14e023..bd9b5d73bc2b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -449,6 +449,10 @@ void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep);
 
 int memcg_update_cache_size(struct kmem_cache *s, int num_groups);
 void memcg_update_array_size(int num_groups);
+
+struct kmem_cache *
+__memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
+
 /**
  * memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
  * @gfp: the gfp allocation flags.
@@ -518,6 +522,37 @@ memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg, int order)
                 __memcg_kmem_commit_charge(page, memcg, order);
 }
 
+/**
+ * memcg_kmem_get_cache: selects the correct per-memcg cache for allocation
+ * @cachep: the original global kmem cache
+ * @gfp: allocation flags.
+ *
+ * This function assumes that the task allocating, which determines the memcg
+ * in the page allocator, belongs to the same cgroup throughout the whole
+ * process.  Misacounting can happen if the task calls memcg_kmem_get_cache()
+ * while belonging to a cgroup, and later on changes. This is considered
+ * acceptable, and should only happen upon task migration.
+ *
+ * Before the cache is created by the memcg core, there is also a possible
+ * imbalance: the task belongs to a memcg, but the cache being allocated from
+ * is the global cache, since the child cache is not yet guaranteed to be
+ * ready. This case is also fine, since in this case the GFP_KMEMCG will not be
+ * passed and the page allocator will not attempt any cgroup accounting.
+ */
+static __always_inline struct kmem_cache *
+memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
+{
+        if (!memcg_kmem_enabled())
+                return cachep;
+        if (gfp & __GFP_NOFAIL)
+                return cachep;
+        if (in_interrupt() || (!current->mm) || (current->flags & PF_KTHREAD))
+                return cachep;
+        if (unlikely(fatal_signal_pending(current)))
+                return cachep;
+
+        return __memcg_kmem_get_cache(cachep, gfp);
+}
 #else
 static inline bool
 memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **memcg, int order)
@@ -553,6 +588,12 @@ static inline void memcg_cache_list_add(struct mem_cgroup *memcg,
                                         struct kmem_cache *s)
 {
 }
+
+static inline struct kmem_cache *
+memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
+{
+        return cachep;
+}
 #endif /* CONFIG_MEMCG_KMEM */
 #endif /* _LINUX_MEMCONTROL_H */