[REF PATCH v3 2/2] mm/slab: decouple the SLAB_OBJ_EXT from MEMCG

[alexs]

From: "Alex Shi (Tencent)" <alexs@xxxxxxxxxx>

commit 21c690a349ba ("mm: introduce slabobj_ext to support slab object
extensions") selected SLAB_OBJ_EXT on MEMCG just for SLAB_MATCH
memcg_data, that included SLAB_OBJ_EXT for MEMCG. In fact, I didn't see
the necessary to enable SLAB_OBJ_EXT for MEMCG.

Let's decouple the SLAB_OBJ_EXT from MEMCG and move out
alloc_slab_obj_exts() definition from SLAB_OBJ_EXT only. To alignment
the alloc_slab_obj_exts() return 0 for good. change its return value to
'-1' for always failed with !SLAB_OBJ_EXT. Now we could save unnecessary
code from MEMCG but !SLAB_OBJ_EXT.

Signed-off-by: Alex Shi (Tencent) <alexs@xxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Yoann Congal <yoann.congal@xxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
---
 init/Kconfig | 1 -
 mm/slab.h    | 6 +++---
 mm/slub.c    | 6 +++---
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 26bf8bb0a7ce..61e43ac9fe75 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -965,7 +965,6 @@ config MEMCG
 	bool "Memory controller"
 	select PAGE_COUNTER
 	select EVENTFD
-	select SLAB_OBJ_EXT
 	help
 	  Provides control over the memory footprint of tasks in a cgroup.
 
diff --git a/mm/slab.h b/mm/slab.h
index 8ffdd4f315f8..6c727ecc1068 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -559,9 +559,6 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
 	return (struct slabobj_ext *)(obj_exts & ~OBJEXTS_FLAGS_MASK);
 }
 
-int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
-                        gfp_t gfp, bool new_slab);
-
 #else /* CONFIG_SLAB_OBJ_EXT */
 
 static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
@@ -571,6 +568,9 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
 
 #endif /* CONFIG_SLAB_OBJ_EXT */
 
+int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
+			gfp_t gfp, bool new_slab);
+
 static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s)
 {
 	return (s->flags & SLAB_RECLAIM_ACCOUNT) ?
diff --git a/mm/slub.c b/mm/slub.c
index cc11f3869cc6..f531c2d67238 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2075,10 +2075,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 
 #else /* CONFIG_SLAB_OBJ_EXT */
 
-static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
-			       gfp_t gfp, bool new_slab)
+int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
+			gfp_t gfp, bool new_slab)
 {
-	return 0;
+	return -1;
 }
 
 static inline void free_slab_obj_exts(struct slab *slab)
-- 
2.43.0