[PATCH 21/23] memcg: Track all the memcg children of a kmem_cache.

[Glauber Costa <glommer@parallels.com>]

From: Suleiman Souhlal <ssouhlal@FreeBSD.org>

This enables us to remove all the children of a kmem_cache being
destroyed, if for example the kernel module it's being used in
gets unloaded. Otherwise, the children will still point to the
destroyed parent.

We also use this to propagate /proc/slabinfo settings to all
the children of a cache, when, for example, changing its
batchsize.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
---
 include/linux/slab.h |    1 +
 mm/slab.c            |   53 ++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 909b508..0dc49fa 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -163,6 +163,7 @@ struct mem_cgroup_cache_params {
 	size_t orig_align;
 	atomic_t refcnt;
 
+	struct list_head sibling_list;
 #endif
 	struct list_head destroyed_list; /* Used when deleting cpuset cache */
 };
diff --git a/mm/slab.c b/mm/slab.c
index ac0916b..86f2275 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2561,6 +2561,7 @@ __kmem_cache_create(struct mem_cgroup *memcg, const char *name, size_t size,
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
 	mem_cgroup_register_cache(memcg, cachep);
 	atomic_set(&cachep->memcg_params.refcnt, 1);
+	INIT_LIST_HEAD(&cachep->memcg_params.sibling_list);
 #endif
 
 	if (setup_cpu_cache(cachep, gfp)) {
@@ -2628,6 +2629,8 @@ kmem_cache_dup(struct mem_cgroup *memcg, struct kmem_cache *cachep)
 		return NULL;
 	}
 
+	list_add(&new->memcg_params.sibling_list,
+	    &cachep->memcg_params.sibling_list);
 	if ((cachep->limit != new->limit) ||
 	    (cachep->batchcount != new->batchcount) ||
 	    (cachep->shared != new->shared))
@@ -2815,6 +2818,29 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 {
 	BUG_ON(!cachep || in_interrupt());
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	/* Destroy all the children caches if we aren't a memcg cache */
+	if (cachep->memcg_params.id != -1) {
+		struct kmem_cache *c;
+		struct mem_cgroup_cache_params *p, *tmp;
+
+		mutex_lock(&cache_chain_mutex);
+		list_for_each_entry_safe(p, tmp,
+		    &cachep->memcg_params.sibling_list, sibling_list) {
+			c = container_of(p, struct kmem_cache, memcg_params);
+			if (c == cachep)
+				continue;
+			mutex_unlock(&cache_chain_mutex);
+			BUG_ON(c->memcg_params.id != -1);
+			mem_cgroup_remove_child_kmem_cache(c,
+			    cachep->memcg_params.id);
+			kmem_cache_destroy(c);
+			mutex_lock(&cache_chain_mutex);
+		}
+		mutex_unlock(&cache_chain_mutex);
+	}
+#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
+
 	/* Find the cache in the chain of caches. */
 	get_online_cpus();
 	mutex_lock(&cache_chain_mutex);
@@ -2822,6 +2848,9 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 	 * the chain is never empty, cache_cache is never destroyed
 	 */
 	list_del(&cachep->next);
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	list_del(&cachep->memcg_params.sibling_list);
+#endif
 	if (__cache_shrink(cachep)) {
 		slab_error(cachep, "Can't free all objects");
 		list_add(&cachep->next, &cache_chain);
@@ -4644,11 +4673,27 @@ static ssize_t slabinfo_write(struct file *file, const char __user *buffer,
 			if (limit < 1 || batchcount < 1 ||
 					batchcount > limit || shared < 0) {
 				res = 0;
-			} else {
-				res = do_tune_cpucache(cachep, limit,
-						       batchcount, shared,
-						       GFP_KERNEL);
+				break;
 			}
+
+			res = do_tune_cpucache(cachep, limit, batchcount,
+			    shared, GFP_KERNEL);
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+			{
+				struct kmem_cache *c;
+				struct mem_cgroup_cache_params *p;
+
+				list_for_each_entry(p,
+				    &cachep->memcg_params.sibling_list,
+				    sibling_list) {
+					c = container_of(p, struct kmem_cache,
+					    memcg_params);
+					do_tune_cpucache(c, limit, batchcount,
+					    shared, GFP_KERNEL);
+				}
+			}
+#endif
 			break;
 		}
 	}
-- 
1.7.7.6