From: Glauber Costa <glommer@parallels.com>
To: Li Zefan <lizefan@huawei.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 13/12] memcg: don't need memcg->memcg_name
Date: Tue, 9 Apr 2013 11:53:50 +0400 [thread overview]
Message-ID: <5163C90E.8040602@parallels.com> (raw)
In-Reply-To: <5163887D.1040809@huawei.com>
On 04/09/2013 07:18 AM, Li Zefan wrote:
>>> @@ -5188,12 +5154,28 @@ static int mem_cgroup_dangling_read(struct cgroup *cont, struct cftype *cft,
>>> struct seq_file *m)
>>> {
>>> struct mem_cgroup *memcg;
>>> + char *memcg_name;
>>> + int ret;
>>> +
>>> + /*
>>> + * cgroup.c will do page-sized allocations most of the time,
>>> + * so we'll just follow the pattern. Also, __get_free_pages
>>> + * is a better interface than kmalloc for us here, because
>>> + * we'd like this memory to be always billed to the root cgroup,
>>> + * not to the process removing the memcg. While kmalloc would
>>> + * require us to wrap it into memcg_stop/resume_kmem_account,
>>> + * with __get_free_pages we just don't pass the memcg flag.
>>> + */
>>> + memcg_name = (char *)__get_free_pages(GFP_KERNEL, 0);
>>> + if (!memcg_name)
>>> + return -ENOMEM;
>>>
>>> mutex_lock(&dangling_memcgs_mutex);
>>>
>>> list_for_each_entry(memcg, &dangling_memcgs, dead) {
>>> - if (memcg->memcg_name)
>>> - seq_printf(m, "%s:\n", memcg->memcg_name);
>>> + ret = cgroup_path(memcg->css.cgroup, memcg_name, PAGE_SIZE);
>>> + if (!ret)
>>> + seq_printf(m, "%s:\n", memcg_name);
>>> else
>>> seq_printf(m, "%p (name lost):\n", memcg);
>>>
>>
>> I'm sorry for dawm question ...when this error happens ?
>> We may get ENAMETOOLONG even with PAGE_SIZE(>=4096bytes) buffer ?
>>
>
> It does no harm to check the return value, and we don't have to
> worry about if cgroup_path() will be changed to return some other
> errno like ENOMEM in the future.
>
I feel more comfortable with the check as well. This is a debugging
interface after all. People tend to resort to this when things go wrong.
So at this point the less assumptions we make, the better.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
prev parent reply other threads:[~2013-04-09 7:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 6:32 [PATCH 0/12][V2] memcg: make memcg's life cycle the same as cgroup Li Zefan
2013-04-08 6:33 ` [PATCH 01/12] memcg: take reference before releasing rcu_read_lock Li Zefan
2013-04-08 6:33 ` [PATCH 02/12] memcg: avoid accessing memcg after releasing reference Li Zefan
2013-04-08 6:33 ` [PATCH 03/12] Revert "memcg: avoid dangling reference count in creation failure." Li Zefan
2013-04-09 2:50 ` Kamezawa Hiroyuki
2013-04-08 6:33 ` [PATCH 04/12] memcg, kmem: fix reference count handling on the error path Li Zefan
2013-04-09 2:51 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 05/12] memcg: use css_get() in sock_update_memcg() Li Zefan
2013-04-08 6:34 ` [PATCH 06/12] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Li Zefan
2013-04-09 2:53 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 07/12] memcg: use css_get/put when charging/uncharging kmem Li Zefan
2013-04-08 14:14 ` Michal Hocko
2013-04-09 2:55 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 08/12] memcg: use css_get/put for swap memcg Li Zefan
2013-04-08 6:35 ` [PATCH 09/12] cgroup: make sure parent won't be destroyed before its children Li Zefan
2013-04-08 15:36 ` Tejun Heo
2013-04-08 6:35 ` [PATCH 10/12] memcg: don't need to get a reference to the parent Li Zefan
2013-04-08 6:36 ` [PATCH 11/12] memcg: kill memcg refcnt Li Zefan
2013-04-08 6:36 ` [PATCH 12/12] memcg: don't need to free memcg via RCU or workqueue Li Zefan
2013-04-08 14:15 ` Michal Hocko
2013-04-09 2:57 ` Kamezawa Hiroyuki
2013-04-08 6:36 ` [PATCH 13/12] memcg: don't need memcg->memcg_name Li Zefan
2013-04-08 14:25 ` Michal Hocko
2013-04-09 1:28 ` Li Zefan
2013-04-09 3:10 ` Kamezawa Hiroyuki
2013-04-09 3:18 ` Li Zefan
2013-04-09 3:46 ` Kamezawa Hiroyuki
2013-04-09 7:55 ` Glauber Costa
2013-04-09 3:59 ` Tejun Heo
2013-04-09 7:53 ` Glauber Costa [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5163C90E.8040602@parallels.com \
--to=glommer@parallels.com \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lizefan@huawei.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox