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Mon, 27 Jun 2022 20:59:07 -0700 (PDT) Message-ID: <17916824-ba97-68ba-8166-9402d5f4440c@openvz.org> Date: Tue, 28 Jun 2022 06:59:06 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH cgroup] cgroup: set the correct return code if hierarchy limits are reached Content-Language: en-US To: Roman Gushchin Cc: Shakeel Butt , =?UTF-8?Q?Michal_Koutn=c3=bd?= , Michal Hocko , Tejun Heo , 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 References: <186d5b5b-a082-3814-9963-bf57dfe08511@openvz.org> From: Vasily Averin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=openvz-org.20210112.gappssmtp.com header.s=20210112 header.b=mxbVmJ++; dmarc=pass (policy=none) header.from=openvz.org; spf=pass (imf03.hostedemail.com: domain of vvs@openvz.org designates 209.85.208.182 as permitted sender) smtp.mailfrom=vvs@openvz.org ARC-Message-Signature: i=1; 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dmarc=pass (policy=none) header.from=openvz.org; spf=pass (imf03.hostedemail.com: domain of vvs@openvz.org designates 209.85.208.182 as permitted sender) smtp.mailfrom=vvs@openvz.org X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1656388750-74392 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 6/28/22 03:44, Roman Gushchin wrote: > On Mon, Jun 27, 2022 at 05:12:55AM +0300, Vasily Averin wrote: >> When cgroup_mkdir reaches the limits of the cgroup hierarchy, it should >> not return -EAGAIN, but instead react similarly to reaching the global >> limit. >> >> Signed-off-by: Vasily Averin >> --- >> kernel/cgroup/cgroup.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c >> index 1be0f81fe8e1..243239553ea3 100644 >> --- a/kernel/cgroup/cgroup.c >> +++ b/kernel/cgroup/cgroup.c >> @@ -5495,7 +5495,7 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode) >> return -ENODEV; >> >> if (!cgroup_check_hierarchy_limits(parent)) { >> - ret = -EAGAIN; >> + ret = -ENOSPC; > > I'd not argue whether ENOSPC is better or worse here, but I don't think we need > to change it now. It's been in this state for a long time and is a part of ABI. > EAGAIN is pretty unique as a mkdir() result, so systemd can handle it well. I would agree with you, however in my opinion EAGAIN is used to restart an interrupted system call. Thus, I worry its return can loop the user space without any chance of continuation. However, maybe I'm confusing something? Thank you, Vasily Averin