From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH v2 1/2] memcg: make cache index determination more robust Date: Fri, 14 Jun 2013 14:04:35 -0400 Message-ID: <1371233076-936-2-git-send-email-glommer@openvz.org> References: <1371233076-936-1-git-send-email-glommer@openvz.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; bh=pm7NlnG2ZFGRBrz1F3UUrDveQUwSo0J0POLCQIgmyOI=; b=wznf463J+xuS0IwXamt3azwML32apzAnaLpP8DqlgfRBOiSOieBIvXf1PvIJMqTU0q pQ796wxbSiIUPrUzNIHv8Xno/ZAdCPeZxOE51Tw9V1rC61eMjvgm8mb58TQ0Ot/oWgPi 4wlNPt7fUjVucciralrDvWn9earetcUpL5/p0M/kADQYtV5oYApylcwnXCal+p+yAkXu Dp7cbQj3PrPZMApAup4E5EleDx2PukB2MMhOALkybpZVxVL8mdahNVtXd+SPMlPQptjO 7IJSDWM6dYaszCn7DCVAZspnR0DuC/hfBhkT1B6cFQw8BKJaqysNCfKBpkiqX1uyZRnI UwTg== In-Reply-To: <1371233076-936-1-git-send-email-glommer-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michal Hocko Cc: linux-mm , cgroups , Johannes Weiner , Andrew Morton , Kamezawa Hiroyuki , Glauber Costa I caught myself doing something like the following outside memcg core: memcg_id = -1; if (memcg && memcg_kmem_is_active(memcg)) memcg_id = memcg_cache_id(memcg); to be able to handle all possible memcgs in a sane manner. In particular, the root cache will have kmemcg_id = -1 (just because we don't call memcg_kmem_init to the root cache since it is not limitable). We have always coped with that by making sure we sanitize which cache is passed to memcg_cache_id. Although this example is given for root, what we really need to know is whether or not a cache is kmem active. But outside the memcg core testing for root, for instance, is not trivial since we don't export mem_cgroup_is_root. I ended up realizing that this tests really belong inside memcg_cache_id. This patch moves a similar but stronger test inside memcg_cache_id and make sure it always return a meaningful value. Signed-off-by: Glauber Costa Cc: Johannes Weiner Cc: Michal Hocko Cc: Kamezawa Hiroyuki --- mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2e851f4..359a53b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3081,7 +3081,9 @@ void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep) */ int memcg_cache_id(struct mem_cgroup *memcg) { - return memcg ? memcg->kmemcg_id : -1; + if (!memcg || !memcg_can_account_kmem(memcg)) + return -1; + return memcg->kmemcg_id; } /* -- 1.8.1.4