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From: Roman Gushchin To: Vasily Averin Cc: Shakeel Butt , Michal =?iso-8859-1?Q?Koutn=FD?= , Michal Hocko , kernel@openvz.org, linux-kernel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, Vlastimil Babka , Muchun Song , cgroups@vger.kernel.org Subject: Re: [PATCH RFC] memcg: notify about global mem_cgroup_id space depletion Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656208572; a=rsa-sha256; cv=none; b=oap3r6YUzk0N9xqUsEL0lb4MuVIw2tcuRJm5xlGgv2MRRthBlACxF7PC/G4tTfzmt4JElw qnrOB6rgapVA/JrLqY+2WmrxezZqpiTvFE+VmFPJZ1SQYXLGxaMOwuTZkKl1oqrNfL1z/D Bfqx+nbr9Nx++wHSuaXsKgRuGURn+1o= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="vBWYqIw/"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.121.223.63 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656208572; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=bjZI8DTIvucVtX5WQZE5x3xoKYG/ekTnBVDG7567Nww=; b=1eXj8WrxgLCWzgsX4OulafBmJEyTq4VUEIqKJxaQDvl5nWLdVG7DoR4JMUiawrL5XbYbBS 0a65DUHEBHqqKlf6Nugq8biGl9M76lPuhKcx6s51teKtct/7rsVuL35DsbYsEmOqJy2tw2 8RJ/iz+h9mUWlE2vZ+ZfTqONgHwIUHA= X-Rspam-User: X-Stat-Signature: 1hy3hx5fe7yyk4gdzwg8odcfwr3qh5rp X-Rspamd-Queue-Id: 854A2180019 Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="vBWYqIw/"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.121.223.63 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev X-Rspamd-Server: rspam03 X-HE-Tag: 1656208572-970944 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Jun 25, 2022 at 05:04:27PM +0300, Vasily Averin wrote: > Currently host owner is not informed about the exhaustion of the > global mem_cgroup_id space. When this happens, systemd cannot > start a new service, but nothing points to the real cause of > this failure. > > Signed-off-by: Vasily Averin > --- > mm/memcontrol.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index d4c606a06bcd..5229321636f2 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5317,6 +5317,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void) > 1, MEM_CGROUP_ID_MAX + 1, GFP_KERNEL); > if (memcg->id.id < 0) { > error = memcg->id.id; > + pr_notice_ratelimited("mem_cgroup_id space is exhausted\n"); > goto fail; > } Hm, in this case it should return -ENOSPC and it's a very unique return code. If it's not returned from the mkdir() call, we should fix this. Otherwise it's up to systemd to handle it properly. I'm not opposing for adding a warning, but parsing dmesg is not how the error handling should be done. Thanks!