Re: [PATCH v3 05/35] mm: introduce slabobj_ext to support slab object extensions

--- a/mm/slab_common.c
+++ b/mm/slab_common.c

@@ -201,6 +201,54 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
 	return NULL;
 }
 
+#ifdef CONFIG_SLAB_OBJ_EXT
+/*
+ * The allocated objcg pointers array is not accounted directly.
+ * Moreover, it should not come from DMA buffer and is not readily
+ * reclaimable. So those GFP bits should be masked off.
+ */
+#define OBJCGS_CLEAR_MASK	(__GFP_DMA | __GFP_RECLAIMABLE | \
+				__GFP_ACCOUNT | __GFP_NOFAIL)
+
+int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
+			gfp_t gfp, bool new_slab)

+{
+	unsigned int objects = objs_per_slab(s, slab);
+	unsigned long obj_exts;
+	void *vec;
+
+	gfp &= ~OBJCGS_CLEAR_MASK;
+	vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp,
+			   slab_nid(slab));
+	if (!vec)
+		return -ENOMEM;
+
+	obj_exts = (unsigned long)vec;
+#ifdef CONFIG_MEMCG
+	obj_exts |= MEMCG_DATA_OBJEXTS;
+#endif
+	if (new_slab) {
+		/*
+		 * If the slab is brand new and nobody can yet access its
+		 * obj_exts, no synchronization is required and obj_exts can
+		 * be simply assigned.
+		 */
+		slab->obj_exts = obj_exts;
+	} else if (cmpxchg(&slab->obj_exts, 0, obj_exts)) {
+		/*
+		 * If the slab is already in use, somebody can allocate and
+		 * assign slabobj_exts in parallel. In this case the existing
+		 * objcg vector should be reused.
+		 */
+		kfree(vec);
+		return 0;
+	}
+
+	kmemleak_not_leak(vec);
+	return 0;
+}
+#endif /* CONFIG_SLAB_OBJ_EXT */
+
 static struct kmem_cache *create_cache(const char *name,
 		unsigned int object_size, unsigned int align,
 		slab_flags_t flags, unsigned int useroffset,

diff --git a/mm/slub.c b/mm/slub.c
index 2ef88bbf56a3..1eb1050814aa 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -683,10 +683,10 @@ static inline bool __slab_update_freelist(struct kmem_cache *s, struct slab *sla
 
 	if (s->flags & __CMPXCHG_DOUBLE) {
 		ret = __update_freelist_fast(slab, freelist_old, counters_old,
-				            freelist_new, counters_new);
+					    freelist_new, counters_new);
 	} else {
 		ret = __update_freelist_slow(slab, freelist_old, counters_old,
-				            freelist_new, counters_new);
+					    freelist_new, counters_new);
 	}
 	if (likely(ret))
 		return true;

@@ -710,13 +710,13 @@ static inline bool slab_update_freelist(struct kmem_cache *s, struct slab *slab,
 
 	if (s->flags & __CMPXCHG_DOUBLE) {
 		ret = __update_freelist_fast(slab, freelist_old, counters_old,
-				            freelist_new, counters_new);
+					    freelist_new, counters_new);
 	} else {
 		unsigned long flags;
 
 		local_irq_save(flags);
 		ret = __update_freelist_slow(slab, freelist_old, counters_old,
-				            freelist_new, counters_new);
+					    freelist_new, counters_new);

 		local_irq_restore(flags);
 	}
 	if (likely(ret))

@@ -1881,13 +1881,25 @@ static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s)
 		NR_SLAB_RECLAIMABLE_B : NR_SLAB_UNRECLAIMABLE_B;
 }
 
-#ifdef CONFIG_MEMCG_KMEM
-static inline void memcg_free_slab_cgroups(struct slab *slab)
+#ifdef CONFIG_SLAB_OBJ_EXT
+static inline void free_slab_obj_exts(struct slab *slab)

@@ -3817,6 +3820,7 @@ void slab_post_alloc_hook(struct kmem_cache *s,	struct obj_cgroup *objcg,
 		kmemleak_alloc_recursive(p[i], s->object_size, 1,
 					 s->flags, init_flags);
 		kmsan_slab_alloc(s, p[i], init_flags);
+		obj_exts = prepare_slab_obj_exts_hook(s, flags, p[i]);