From: Vladimir Davydov <vdavydov@parallels.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <mhocko@suse.cz>,
<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] memcg: fix mutex not unlocked on memcg_create_kmem_cache fail path
Date: Fri, 31 Jan 2014 10:53:47 +0400 [thread overview]
Message-ID: <52EB487B.6040701@parallels.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1401301438500.12223@chino.kir.corp.google.com>
Hi, David
Thank you for taking look at this and adding the missing patch
description. WRT your patch, please see the comment inline.
On 01/31/2014 02:39 AM, David Rientjes wrote:
> 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);
> +
This looks cumbersome, IMO. Let's leave it as is for now. AFAIK,
cgroup_name() will be reworked soon so that it won't require RCU-context
(https://lkml.org/lkml/2014/1/28/530). Therefore, it will be possible to
get rid of this pointless tmp_name allocation by making
kmem_cache_create_memcg() take not just name, but printf-like format +
vargs.
Thanks.
next prev parent reply other threads:[~2014-01-31 6:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-30 16:01 [PATCH] memcg: fix mutex not unlocked on memcg_create_kmem_cache fail path Vladimir Davydov
2014-01-30 21:01 ` Andrew Morton
2014-01-30 21:14 ` David Rientjes
2014-01-30 21:29 ` Andrew Morton
2014-01-30 21:38 ` David Rientjes
2014-01-30 21:50 ` Andrew Morton
2014-01-30 22:04 ` David Rientjes
2014-01-30 22:09 ` Andrew Morton
2014-01-30 22:13 ` David Rientjes
2014-01-30 22:15 ` Andrew Morton
2014-01-30 22:39 ` David Rientjes
2014-01-31 6:53 ` Vladimir Davydov [this message]
2014-01-31 10:42 ` David Rientjes
2014-01-31 11:29 ` Vladimir Davydov
2014-01-30 21:36 ` David Rientjes
2014-01-30 21:09 ` David Rientjes
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