[PATCH 04/16] mm: memcg/slab: allocate space for memcg ownership data for non-root slabs

[Roman Gushchin]

Allocate and release memory for storing the memcg ownership data.
For each slab page allocate space sufficient for number_of_objects
pointers to struct mem_cgroup_vec.

The mem_cgroup field of the struct page isn't used for slab pages,
so let's use the space for storing the pointer for the allocated
space.

This commit makes sure that the space is ready for use, but nobody
is actually using it yet. Following commits in the series will fix it.

Signed-off-by: Roman Gushchin <guro@xxxxxx>
---
 include/linux/mm_types.h |  5 ++++-
 mm/slab.c                |  3 ++-
 mm/slab.h                | 37 ++++++++++++++++++++++++++++++++++++-
 mm/slub.c                |  2 +-
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 2222fa795284..4d99ee5a9c53 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -198,7 +198,10 @@ struct page {
 	atomic_t _refcount;
 
 #ifdef CONFIG_MEMCG
-	struct mem_cgroup *mem_cgroup;
+	union {
+		struct mem_cgroup *mem_cgroup;
+		struct mem_cgroup_ptr **mem_cgroup_vec;
+	};
 #endif
 
 	/*
diff --git a/mm/slab.c b/mm/slab.c
index f1e1840af533..ffa16dd966ef 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1370,7 +1370,8 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
 		return NULL;
 	}
 
-	if (charge_slab_page(page, flags, cachep->gfporder, cachep)) {
+	if (charge_slab_page(page, flags, cachep->gfporder, cachep,
+			     cachep->num)) {
 		__free_pages(page, cachep->gfporder);
 		return NULL;
 	}
diff --git a/mm/slab.h b/mm/slab.h
index 03833b02b9ae..8620a0a1d5fa 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -406,6 +406,23 @@ static __always_inline void memcg_uncharge_slab(struct page *page, int order,
 	percpu_ref_put_many(&s->memcg_params.refcnt, 1 << order);
 }
 
+static inline int memcg_alloc_page_memcg_vec(struct page *page, gfp_t gfp,
+					     unsigned int objects)
+{
+	page->mem_cgroup_vec = kmalloc(sizeof(struct mem_cgroup_ptr *) *
+				       objects, gfp | __GFP_ZERO);
+	if (!page->mem_cgroup_vec)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static inline void memcg_free_page_memcg_vec(struct page *page)
+{
+	kfree(page->mem_cgroup_vec);
+	page->mem_cgroup_vec = NULL;
+}
+
 extern void slab_init_memcg_params(struct kmem_cache *);
 extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
 
@@ -455,6 +472,16 @@ static inline void memcg_uncharge_slab(struct page *page, int order,
 {
 }
 
+static inline int memcg_alloc_page_memcg_vec(struct page *page, gfp_t gfp,
+					     unsigned int objects)
+{
+	return 0;
+}
+
+static inline void memcg_free_page_memcg_vec(struct page *page)
+{
+}
+
 static inline void slab_init_memcg_params(struct kmem_cache *s)
 {
 }
@@ -479,14 +506,21 @@ static inline struct kmem_cache *virt_to_cache(const void *obj)
 
 static __always_inline int charge_slab_page(struct page *page,
 					    gfp_t gfp, int order,
-					    struct kmem_cache *s)
+					    struct kmem_cache *s,
+					    unsigned int objects)
 {
+	int ret;
+
 	if (is_root_cache(s)) {
 		mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
 				    PAGE_SIZE << order);
 		return 0;
 	}
 
+	ret = memcg_alloc_page_memcg_vec(page, gfp, objects);
+	if (ret)
+		return ret;
+
 	return memcg_charge_slab(page, gfp, order, s);
 }
 
@@ -499,6 +533,7 @@ static __always_inline void uncharge_slab_page(struct page *page, int order,
 		return;
 	}
 
+	memcg_free_page_memcg_vec(page);
 	memcg_uncharge_slab(page, order, s);
 }
 
diff --git a/mm/slub.c b/mm/slub.c
index bd902d65a71c..e810582f5b86 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1518,7 +1518,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s,
 	else
 		page = __alloc_pages_node(node, flags, order);
 
-	if (page && charge_slab_page(page, flags, order, s)) {
+	if (page && charge_slab_page(page, flags, order, s, oo_objects(oo))) {
 		__free_pages(page, order);
 		page = NULL;
 	}
-- 
2.21.0