linux-kernel - [PATCH -mm 3/6] slab: use css id for naming per memcg caches

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Date:	Fri, 16 Jan 2015 17:13:03 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH -mm 3/6] slab: use css id for naming per memcg caches

Currently, we use mem_cgroup->kmemcg_id to guarantee kmem_cache->name
uniqueness. This is correct, because kmemcg_id is only released on css
free after destroying all per memcg caches.

However, I am going to change that and release kmemcg_id on css offline,
because it is not wise to keep it for so long, wasting valuable entries
of memcg_cache_params->memcg_caches arrays. Therefore, to preserve cache
name uniqueness, let us switch to css->id.

Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
---
 mm/slab_common.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index fe99859ba34c..512ee119e5c3 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -487,6 +487,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
 			     struct kmem_cache *root_cache)
 {
 	static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */
+	struct cgroup_subsys_state *css = mem_cgroup_css(memcg);
 	struct memcg_cache_array *arr;
 	struct kmem_cache *s = NULL;
 	char *cache_name;
@@ -509,10 +510,9 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
 	if (arr->entries[idx])
 		goto out_unlock;
 
-	cgroup_name(mem_cgroup_css(memcg)->cgroup,
-		    memcg_name_buf, sizeof(memcg_name_buf));
+	cgroup_name(css->cgroup, memcg_name_buf, sizeof(memcg_name_buf));
 	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
-			       idx, memcg_name_buf);
+			       css->id, memcg_name_buf);
 	if (!cache_name)
 		goto out_unlock;
 
-- 
1.7.10.4

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