From: Michal Hocko <mhocko@suse.cz> To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Johannes Weiner <hannes@cmpxchg.org>, Ying Han <yinghan@google.com>, Tejun Heo <htejun@gmail.com>, Glauber Costa <glommer@parallels.com>, Li Zefan <lizefan@huawei.com> Subject: [PATCH v3 2/7] memcg: keep prev's css alive for the whole mem_cgroup_iter Date: Thu, 3 Jan 2013 18:54:16 +0100 [thread overview] Message-ID: <1357235661-29564-3-git-send-email-mhocko@suse.cz> (raw) In-Reply-To: <1357235661-29564-1-git-send-email-mhocko@suse.cz> css reference counting keeps the cgroup alive even though it has been already removed. mem_cgroup_iter relies on this fact and takes a reference to the returned group. The reference is then released on the next iteration or mem_cgroup_iter_break. mem_cgroup_iter currently releases the reference right after it gets the last css_id. This is correct because neither prev's memcg nor cgroup are accessed after then. This will change in the next patch so we need to hold the group alive a bit longer so let's move the css_put at the end of the function. Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e71cfde..90a3b1d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1143,12 +1143,9 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, if (prev && !reclaim) id = css_id(&prev->css); - if (prev && prev != root) - css_put(&prev->css); - if (!root->use_hierarchy && root != root_mem_cgroup) { if (prev) - return NULL; + goto out_css_put; return root; } @@ -1166,7 +1163,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, spin_lock(&iter->iter_lock); if (prev && reclaim->generation != iter->generation) { spin_unlock(&iter->iter_lock); - return NULL; + goto out_css_put; } id = iter->position; } @@ -1190,8 +1187,12 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, } if (prev && !css) - return NULL; + goto out_css_put; } +out_css_put: + if (prev && prev != root) + css_put(&prev->css); + return memcg; } -- 1.7.10.4
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@suse.cz> To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Johannes Weiner <hannes@cmpxchg.org>, Ying Han <yinghan@google.com>, Tejun Heo <htejun@gmail.com>, Glauber Costa <glommer@parallels.com>, Li Zefan <lizefan@huawei.com> Subject: [PATCH v3 2/7] memcg: keep prev's css alive for the whole mem_cgroup_iter Date: Thu, 3 Jan 2013 18:54:16 +0100 [thread overview] Message-ID: <1357235661-29564-3-git-send-email-mhocko@suse.cz> (raw) In-Reply-To: <1357235661-29564-1-git-send-email-mhocko@suse.cz> css reference counting keeps the cgroup alive even though it has been already removed. mem_cgroup_iter relies on this fact and takes a reference to the returned group. The reference is then released on the next iteration or mem_cgroup_iter_break. mem_cgroup_iter currently releases the reference right after it gets the last css_id. This is correct because neither prev's memcg nor cgroup are accessed after then. This will change in the next patch so we need to hold the group alive a bit longer so let's move the css_put at the end of the function. Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e71cfde..90a3b1d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1143,12 +1143,9 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, if (prev && !reclaim) id = css_id(&prev->css); - if (prev && prev != root) - css_put(&prev->css); - if (!root->use_hierarchy && root != root_mem_cgroup) { if (prev) - return NULL; + goto out_css_put; return root; } @@ -1166,7 +1163,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, spin_lock(&iter->iter_lock); if (prev && reclaim->generation != iter->generation) { spin_unlock(&iter->iter_lock); - return NULL; + goto out_css_put; } id = iter->position; } @@ -1190,8 +1187,12 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, } if (prev && !css) - return NULL; + goto out_css_put; } +out_css_put: + if (prev && prev != root) + css_put(&prev->css); + return memcg; } -- 1.7.10.4 -- 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>
next prev parent reply other threads:[~2013-01-03 17:54 UTC|newest] Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-01-03 17:54 [PATCH v3 0/7] rework mem_cgroup iterator Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-03 17:54 ` [PATCH v3 1/7] memcg: synchronize per-zone iterator access by a spinlock Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-03 17:54 ` Michal Hocko [this message] 2013-01-03 17:54 ` [PATCH v3 2/7] memcg: keep prev's css alive for the whole mem_cgroup_iter Michal Hocko 2013-01-03 17:54 ` [PATCH v3 3/7] memcg: rework mem_cgroup_iter to use cgroup iterators Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-03 17:54 ` [PATCH v3 4/7] memcg: remove memcg from the reclaim iterators Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-07 6:18 ` Kamezawa Hiroyuki 2013-01-07 6:18 ` Kamezawa Hiroyuki 2013-02-08 19:33 ` Johannes Weiner 2013-02-08 19:33 ` Johannes Weiner 2013-02-11 15:16 ` Michal Hocko 2013-02-11 15:16 ` Michal Hocko 2013-02-11 17:56 ` Johannes Weiner 2013-02-11 17:56 ` Johannes Weiner 2013-02-11 19:29 ` Michal Hocko 2013-02-11 19:29 ` Michal Hocko 2013-02-11 19:58 ` Johannes Weiner 2013-02-11 19:58 ` Johannes Weiner 2013-02-11 21:27 ` Michal Hocko 2013-02-11 21:27 ` Michal Hocko 2013-02-11 22:07 ` Michal Hocko 2013-02-11 22:07 ` Michal Hocko 2013-02-11 22:39 ` Johannes Weiner 2013-02-11 22:39 ` Johannes Weiner 2013-02-12 9:54 ` Michal Hocko 2013-02-12 9:54 ` Michal Hocko 2013-02-12 15:10 ` Johannes Weiner 2013-02-12 15:10 ` Johannes Weiner 2013-02-12 15:43 ` Michal Hocko 2013-02-12 15:43 ` Michal Hocko 2013-02-12 16:10 ` Paul E. McKenney 2013-02-12 16:10 ` Paul E. McKenney 2013-02-12 17:25 ` Johannes Weiner 2013-02-12 17:25 ` Johannes Weiner 2013-02-12 18:31 ` Paul E. McKenney 2013-02-12 18:31 ` Paul E. McKenney 2013-02-12 19:53 ` Johannes Weiner 2013-02-12 19:53 ` Johannes Weiner 2013-02-13 9:51 ` Michal Hocko 2013-02-13 9:51 ` Michal Hocko 2013-02-12 17:56 ` Michal Hocko 2013-02-12 17:56 ` Michal Hocko 2013-02-12 16:13 ` Michal Hocko 2013-02-12 16:13 ` Michal Hocko 2013-02-12 16:24 ` Michal Hocko 2013-02-12 16:24 ` Michal Hocko 2013-02-12 16:37 ` Michal Hocko 2013-02-12 16:37 ` Michal Hocko 2013-02-12 16:41 ` Johannes Weiner 2013-02-12 16:41 ` Johannes Weiner 2013-02-12 17:12 ` Michal Hocko 2013-02-12 17:12 ` Michal Hocko 2013-02-12 17:37 ` Johannes Weiner 2013-02-12 17:37 ` Johannes Weiner 2013-02-13 8:11 ` Glauber Costa 2013-02-13 8:11 ` Glauber Costa 2013-02-13 10:38 ` Michal Hocko 2013-02-13 10:38 ` Michal Hocko 2013-02-13 10:34 ` Michal Hocko 2013-02-13 10:34 ` Michal Hocko 2013-02-13 12:56 ` Michal Hocko 2013-02-13 12:56 ` Michal Hocko 2013-02-12 16:33 ` Johannes Weiner 2013-02-12 16:33 ` Johannes Weiner 2013-01-03 17:54 ` [PATCH v3 5/7] memcg: simplify mem_cgroup_iter Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-03 17:54 ` [PATCH v3 6/7] memcg: further " Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-03 17:54 ` [PATCH v3 7/7] cgroup: remove css_get_next Michal Hocko 2013-01-03 17:54 ` Michal Hocko 2013-01-04 3:42 ` Li Zefan 2013-01-04 3:42 ` Li Zefan 2013-01-23 12:52 ` [PATCH v3 0/7] rework mem_cgroup iterator Michal Hocko 2013-01-23 12:52 ` Michal Hocko
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=1357235661-29564-3-git-send-email-mhocko@suse.cz \ --to=mhocko@suse.cz \ --cc=glommer@parallels.com \ --cc=hannes@cmpxchg.org \ --cc=htejun@gmail.com \ --cc=kamezawa.hiroyu@jp.fujitsu.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=lizefan@huawei.com \ --cc=yinghan@google.com \ /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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.