mm: shrinker: make shrinker not depend on memcg kmem

Currently shrinker is just allocated and can work when memcg kmem is
enabled.  But, THP deferred split shrinker is not slab shrinker, it
doesn't make too much sense to have such shrinker depend on memcg kmem.
It should be able to reclaim THP even though memcg kmem is disabled.

Introduce a new shrinker flag, SHRINKER_NONSLAB, for non-slab shrinker.
When memcg kmem is disabled, just such shrinkers can be called in
shrinking memcg slab.

[yang.shi@linux.alibaba.com: add comment]
  Link: http://lkml.kernel.org/r/1566496227-84952-4-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1565144277-36240-4-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 17 insertions, 9 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ad8f1a397ae4..a3c0a639c824 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -128,9 +128,8 @@ struct mem_cgroup_per_node {
 
         struct mem_cgroup_reclaim_iter  iter[DEF_PRIORITY + 1];
 
-#ifdef CONFIG_MEMCG_KMEM
         struct memcg_shrinker_map __rcu *shrinker_map;
-#endif
+
         struct rb_node          tree_node;      /* RB tree node */
         unsigned long           usage_in_excess;/* Set to the value by which */
                                                 /* the soft limit is exceeded*/
@@ -1311,6 +1310,11 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
         } while ((memcg = parent_mem_cgroup(memcg)));
         return false;
 }
+
+extern int memcg_expand_shrinker_maps(int new_id);
+
+extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
+                                   int nid, int shrinker_id);
 #else
 #define mem_cgroup_sockets_enabled 0
 static inline void mem_cgroup_sk_alloc(struct sock *sk) { };
@@ -1319,6 +1323,11 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 {
         return false;
 }
+
+static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
+                                          int nid, int shrinker_id)
+{
+}
 #endif
 
 struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
@@ -1390,10 +1399,6 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
         return memcg ? memcg->kmemcg_id : -1;
 }
 
-extern int memcg_expand_shrinker_maps(int new_id);
-
-extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
-                                   int nid, int shrinker_id);
 #else
 
 static inline int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
@@ -1435,8 +1440,6 @@ static inline void memcg_put_cache_ids(void)
 {
 }
 
-static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
-                                          int nid, int shrinker_id) { }
 #endif /* CONFIG_MEMCG_KMEM */
 
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 9443cafd1969..0f80123650e2 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -69,7 +69,7 @@ struct shrinker {
 
         /* These are for internal use */
         struct list_head list;
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
         /* ID in shrinker_idr */
         int id;
 #endif
@@ -81,6 +81,11 @@ struct shrinker {
 /* Flags */
 #define SHRINKER_NUMA_AWARE     (1 << 0)
 #define SHRINKER_MEMCG_AWARE    (1 << 1)
+/*
+ * It just makes sense when the shrinker is also MEMCG_AWARE for now,
+ * non-MEMCG_AWARE shrinker should not have this flag set.
+ */
+#define SHRINKER_NONSLAB        (1 << 2)
 
 extern int prealloc_shrinker(struct shrinker *shrinker);
 extern void register_shrinker_prepared(struct shrinker *shrinker);