On Thu, 30 Jan 2014, Andrew Morton wrote:
> > It always was.
>
> eh? kmem_cache_create_memcg()'s kstrdup() will allocate the minimum
> needed amount of memory.
>
Ah, good point. We could this incrementally on my patch:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -637,6 +637,9 @@ int memcg_limited_groups_array_size;
* better kept as an internal representation in cgroup.c. In any case, the
* cgrp_id space is not getting any smaller, and we don't have to necessarily
* increase ours as well if it increases.
+ *
+ * Updates to MAX_SIZE should update the space for the memcg name in
+ * memcg_create_kmem_cache().
*/
#define MEMCG_CACHES_MIN_SIZE 4
#define MEMCG_CACHES_MAX_SIZE MEM_CGROUP_ID_MAX
@@ -3400,8 +3403,10 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
struct kmem_cache *s)
{
- char *name = NULL;
struct kmem_cache *new;
+ const char *cgrp_name;
+ char *name = NULL;
+ size_t len;
BUG_ON(!memcg_can_account_kmem(memcg));
@@ -3409,9 +3414,22 @@ static struct kmem_cache *memcg_create_kmem_cache(struct
mem_cgroup *memcg,
if (unlikely(!name))
return NULL;
+ /*
+ * Format of a memcg's kmem cache name:
+ * <cache-name>(<memcg-id>:<cgroup-name>)
+ */
+ len = strlen(s->name);
+ /* Space for parentheses, colon, terminator */
+ len += 4;
+ /* MEMCG_CACHES_MAX_SIZE is USHRT_MAX */
+ len += 5;
+ BUILD_BUG_ON(MEMCG_CACHES_MAX_SIZE > USHRT_MAX);
+
rcu_read_lock();
- snprintf(name, PATH_MAX, "%s(%d:%s)", s->name, memcg_cache_id(memcg),
- cgroup_name(memcg->css.cgroup));
+ cgrp_name = cgroup_name(memcg->css.cgroup);
+ len += strlen(cgrp_name);
+ snprintf(name, len, "%s(%d:%s)", s->name, memcg_cache_id(memcg),
+ cgrp_name);
rcu_read_unlock();
new = kmem_cache_create_memcg(memcg, name, s->object_size, s->align,
--
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