From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DF63C43334 for ; Tue, 28 Jun 2022 03:59:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244150AbiF1D7M (ORCPT ); Mon, 27 Jun 2022 23:59:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244143AbiF1D7L (ORCPT ); Mon, 27 Jun 2022 23:59:11 -0400 Received: from mail-lj1-x236.google.com (mail-lj1-x236.google.com [IPv6:2a00:1450:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80A9528E02 for ; Mon, 27 Jun 2022 20:59:09 -0700 (PDT) Received: by mail-lj1-x236.google.com with SMTP id a11so13348474ljb.5 for ; Mon, 27 Jun 2022 20:59:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=openvz-org.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=MFS2x9pNQLwXGwuNgzQ1iIUHTuj+zHNF+6//GrDccok=; b=mxbVmJ++2Cc5/l/lqWx9Fs7t2Zg7/rpqevzlWyOhXZcy9grpe35G9l9ySScKLev9uU Dz4LDLeUYcVPDUSNls7Ymx0CeJl3DwKUSThgh4DQBTI8XLC2NylaXNKQahTJuNrrhUjh aREqf+FUffagdLwymwDwlWSSZTJY8wZ/FbaTDj6Cjw5imW4HlIy0AFuvLVetwmwNEHvp qh5Lj5ek3pFqkm0PtNrDLngV8a5QKRAFrMwMy8CK7R61VAE541rKqNoB9E4tl9f5IEsO KlC6BIKb6Pz11uDudiW1HiZtesTcxv+lpD+FqTR2LY+0s3ApEMvSGfdZXdhf8T98XTo0 pVEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=MFS2x9pNQLwXGwuNgzQ1iIUHTuj+zHNF+6//GrDccok=; b=USIUGgjMrzkHqeTnM+vdhBl9IYxcrbs1uwq2bsCuXivt7IJ9/gsPa7iiyw3ZyFMi9X 5y2tMdIfBiRSnzIpymKivZbciWhwhymg5+yOmbsEQgyUNN2ZJ2MeNnNimzy5RnITJGE/ weg6mYDC0e5oqmCgZWDCmitG/IuYuuF8RWsfYC5i3vrWe4Egw9dVrQlSEshHTgo5g2nr Rc5Fa9JfwpXFSh4xpOsQcVVTF9DdwQzwFpS7bT0mHIIOGFUWF4lIIvDFibWaZxC5MnIw fhzLlK/hx1YD+lR0v8Vgz907ay7e7CSyDtd/CbrhFmn9DN0tL68wuwQy8ObX76qDdEbu hXnQ== X-Gm-Message-State: AJIora8gr+JlcypBK8XZxx8FSQA1W2DOIGcNeaxQtG96qiszZZIONqAK SvCFC2QAOf36n3gcYt83sqlCum25tu9KjQ== X-Google-Smtp-Source: AGRyM1v+P/2CJeZ+6sSIGo0bMtoNBlqMfhE/1f+IChMa8AR46nz3yFZFoohHBHPpjnE3p8uTTovsEQ== X-Received: by 2002:a05:651c:19aa:b0:25b:d22a:dfc7 with SMTP id bx42-20020a05651c19aa00b0025bd22adfc7mr1008009ljb.410.1656388747749; Mon, 27 Jun 2022 20:59:07 -0700 (PDT) Received: from [192.168.1.65] ([46.188.121.129]) by smtp.gmail.com with ESMTPSA id s13-20020a05651c200d00b0025a928f3d63sm1586153ljo.61.2022.06.27.20.59.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasily Averin Subject: Re: [PATCH cgroup] cgroup: set the correct return code if hierarchy limits are reached Date: Tue, 28 Jun 2022 06:59:06 +0300 Message-ID: <17916824-ba97-68ba-8166-9402d5f4440c@openvz.org> References: <186d5b5b-a082-3814-9963-bf57dfe08511@openvz.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=openvz-org.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=MFS2x9pNQLwXGwuNgzQ1iIUHTuj+zHNF+6//GrDccok=; b=mxbVmJ++2Cc5/l/lqWx9Fs7t2Zg7/rpqevzlWyOhXZcy9grpe35G9l9ySScKLev9uU Dz4LDLeUYcVPDUSNls7Ymx0CeJl3DwKUSThgh4DQBTI8XLC2NylaXNKQahTJuNrrhUjh aREqf+FUffagdLwymwDwlWSSZTJY8wZ/FbaTDj6Cjw5imW4HlIy0AFuvLVetwmwNEHvp qh5Lj5ek3pFqkm0PtNrDLngV8a5QKRAFrMwMy8CK7R61VAE541rKqNoB9E4tl9f5IEsO KlC6BIKb6Pz11uDudiW1HiZtesTcxv+lpD+FqTR2LY+0s3ApEMvSGfdZXdhf8T98XTo0 pVEw== Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" To: Roman Gushchin Cc: Shakeel Butt , =?UTF-8?Q?Michal_Koutn=c3=bd?= , Michal Hocko , Tejun Heo , Zefan Li , Johannes Weiner , kernel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Vlastimil Babka , Muchun Song , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org 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