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Wed, 29 Jun 2022 12:25:59 -0700 (PDT) Date: Thu, 30 Jun 2022 04:25:57 +0900 From: Tejun Heo To: Vasily Averin Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , Roman Gushchin , Shakeel Butt , Michal Hocko , Zefan Li , Johannes Weiner , 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 cgroup] cgroup: set the correct return code if hierarchy limits are reached Message-ID: References: <186d5b5b-a082-3814-9963-bf57dfe08511@openvz.org> <17916824-ba97-68ba-8166-9402d5f4440c@openvz.org> <20220628091648.GA12249@blackbody.suse.cz> <525a3eea-8431-64ad-e464-5503f3297722@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <525a3eea-8431-64ad-e464-5503f3297722@openvz.org> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656530761; a=rsa-sha256; cv=none; b=EyoyMiP3Hlj+Lj7J4dFtFlWhp3Q3RkvukG8CpQAcJuY1XuHCUkHPm94M+CmYprNx7Cd5IP 75cCqOJbzdmKlKk7Yyp4iTknk++KaqXkdK1y2TlQOYFvZf3wA5rv5nJt0XSjTNCSKs1DEx N29uDl+yq9iHISMwsLwY6xYNA59+YjY= ARC-Authentication-Results: i=1; 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dkim=pass header.d=gmail.com header.s=20210112 header.b=V9dUu8Wt; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=pass (imf26.hostedemail.com: domain of htejun@gmail.com designates 209.85.210.169 as permitted sender) smtp.mailfrom=htejun@gmail.com X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1656530761-214889 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 Wed, Jun 29, 2022 at 09:13:02AM +0300, Vasily Averin wrote: > I experimented on fedora36 node with LXC and centos stream 9 container. > and I did not noticed any critical systemd troubles with original -EAGAIN. > When cgroup's limit is reached systemd cannot start new services, > for example lxc-attach generates following output: > > [root@fc34-vvs ~]# lxc-attach c9s > lxc-attach: c9s: cgroups/cgfsng.c: cgroup_attach_leaf: 2084 Resource temporarily unavailable - Failed to create leaf cgroup ".lxc" > lxc-attach: c9s: cgroups/cgfsng.c: __cgroup_attach_many: 3517 Resource temporarily unavailable - Failed to attach to cgroup fd 11 > lxc-attach: c9s: attach.c: lxc_attach: 1679 Resource temporarily unavailable - Failed to attach cgroup > lxc-attach: c9s: attach.c: do_attach: 1237 No data available - Failed to receive lsm label fd > lxc-attach: c9s: attach.c: do_attach: 1375 Failed to attach to container > > I did not found any loop in userspace caused by EAGAIN. > Messages looks unclear, however situation with the patched kernel is not much better: > > [root@fc34-vvs ~]# lxc-attach c9s > lxc-attach: c9s: cgroups/cgfsng.c: cgroup_attach_leaf: 2084 No space left on device - Failed to create leaf cgroup ".lxc" > lxc-attach: c9s: cgroups/cgfsng.c: __cgroup_attach_many: 3517 No space left on device - Failed to attach to cgroup fd 11 > lxc-attach: c9s: attach.c: lxc_attach: 1679 No space left on device - Failed to attach cgroup > lxc-attach: c9s: attach.c: do_attach: 1237 No data available - Failed to receive lsm label fd > lxc-attach: c9s: attach.c: do_attach: 1375 Failed to attach to container I'd say "resource temporarily unavailable" is better fitting than "no space left on device" and the syscall restart thing isn't handled by -EAGAIN return value. Grep restart_block for that. Thanks. -- tejun