mm: memcg/slab: uncharge during kmem_cache_free_bulk()

commit d1b2cf6 upstream.

Object cgroup charging is done for all the objects during allocation, but
during freeing, uncharging ends up happening for only one object in the
case of bulk allocation/freeing.

Fix this by having a separate call to uncharge all the objects from
kmem_cache_free_bulk() and by modifying memcg_slab_free_hook() to take
care of bulk uncharging.

Fixes: 964d4bd ("mm: memcg/slab: save obj_cgroup for non-root slab objects"
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201009060423.390479-1-bharata@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/slab.c

@@ -3440,7 +3440,7 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
 		memset(objp, 0, cachep->object_size);
 	kmemleak_free_recursive(objp, cachep->flags);
 	objp = cache_free_debugcheck(cachep, objp, caller);
-	memcg_slab_free_hook(cachep, virt_to_head_page(objp), objp);
+	memcg_slab_free_hook(cachep, &objp, 1);
 
 	/*
 	 * Skip calling cache_free_alien() when the platform is not numa.

mm/slab.h

@@ -345,30 +345,42 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
 	obj_cgroup_put(objcg);
 }
 
-static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
-					void *p)
+static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
+					void **p, int objects)
 {
+	struct kmem_cache *s;
 	struct obj_cgroup *objcg;
+	struct page *page;
 	unsigned int off;
+	int i;
 
 	if (!memcg_kmem_enabled())
 		return;
 
-	if (!page_has_obj_cgroups(page))
-		return;
+	for (i = 0; i < objects; i++) {
+		if (unlikely(!p[i]))
+			continue;
 
-	off = obj_to_index(s, page, p);
-	objcg = page_obj_cgroups(page)[off];
-	page_obj_cgroups(page)[off] = NULL;
+		page = virt_to_head_page(p[i]);
+		if (!page_has_obj_cgroups(page))
+			continue;
 
-	if (!objcg)
-		return;
+		if (!s_orig)
+			s = page->slab_cache;
+		else
+			s = s_orig;
 
-	obj_cgroup_uncharge(objcg, obj_full_size(s));
-	mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s),
-			-obj_full_size(s));
+		off = obj_to_index(s, page, p[i]);
+		objcg = page_obj_cgroups(page)[off];
+		if (!objcg)
+			continue;
 
-	obj_cgroup_put(objcg);
+		page_obj_cgroups(page)[off] = NULL;
+		obj_cgroup_uncharge(objcg, obj_full_size(s));
+		mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s),
+				-obj_full_size(s));
+		obj_cgroup_put(objcg);
+	}
 }
 
 #else /* CONFIG_MEMCG_KMEM */
@@ -406,8 +418,8 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
 {
 }
 
-static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
-					void *p)
+static inline void memcg_slab_free_hook(struct kmem_cache *s,
+					void **p, int objects)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */

mm/slub.c

@@ -3091,7 +3091,7 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
 	struct kmem_cache_cpu *c;
 	unsigned long tid;
 
-	memcg_slab_free_hook(s, page, head);
+	memcg_slab_free_hook(s, &head, 1);
 redo:
 	/*
 	 * Determine the currently cpus per cpu slab.
@@ -3253,6 +3253,7 @@ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
 	if (WARN_ON(!size))
 		return;
 
+	memcg_slab_free_hook(s, p, size);
 	do {
 		struct detached_freelist df;