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 X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DAB7C76191 for ; Wed, 24 Jul 2019 17:38:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5823321926 for ; Wed, 24 Jul 2019 17:38:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563989880; bh=HU+UJEwKj7oJ8yx1arDBtwt//GkoHkAe1Tgtv1vNwIE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=yRZF6hZpw8q4cILU8ZRFqf7ogajX2ROD5d8pbC236teavPgZHceuj0LXn+oROBCKk gZ3IJL3ztlpFM7xJq7rnfhKP5xdP9pvKjXEc0tYYfE1EUvyi4eYinyF0692hYRBVce ooxVJWeyN3T6Xt+2Ccrg5DP7svTQ3BDQ9WmPDecE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728734AbfGXRh7 (ORCPT ); Wed, 24 Jul 2019 13:37:59 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:44995 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726323AbfGXRh6 (ORCPT ); Wed, 24 Jul 2019 13:37:58 -0400 Received: by mail-pl1-f196.google.com with SMTP id t14so22248469plr.11; Wed, 24 Jul 2019 10:37:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=210jieYj6x4iDn+RzSO4QMxbDZOJTaHp79XKUEHy4po=; b=hEIOZzj60rL78OaSsU8W3pEv0nJLPBgdwJhBm+OTrlPQ4Dd28EfK2xeqNvC+YGG1iS o7+D047hKFmZkjPSVvrcm81oE1rDcz+IZmg6FJ/axEGwNDZR95o5vSzbXgpbwrf2/mfc z8SddeI9szOe6KIUJ7vMY/XhgwLeyq8qXJzegLuhJRZrhtXpnYfG93bp8qHbj5Z5m+BC eGqOrfAFGREptDwpyg3OOnPOGiQK1kk2OIYuZ8WwuEv+wR1kuDyJz5E4YTlRTomysIRU LP0OHdDIafKLY5KlYpdPJE9e41tYkm7y46iWC3NOVLtZveI4poFnX5aOg9hOiMzgpwn/ +9/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=210jieYj6x4iDn+RzSO4QMxbDZOJTaHp79XKUEHy4po=; b=P/C3R4isLq1o+mFXfYrNrFyhzJb4hVbwYxGkWIXXSZE598Jfs1hsROXWBnMwkpWtI2 yqJgLry+LuF+QAUoCEkKV7uobc+mZGOiT9I65ptD8lRgnGUyvLHN0+15nT+taQMwQBs1 BgUizfAy2AFkgqul34xw8HkSZ+MaOv4adeBKduTBZRGvv6f+LrTIcwYAFEDKmbISm0vl I8++DR39U/1mS9MSdnO1GWXRIszaMWugCZUPNSFR7NtTwf5hUCBvAJrT/F/N50IX/MJQ z6CPnJ2z4ir7JdZFcs/JZQo4ETGnFZP4W9RI1krTU9vQ1oPEgdHQedi4ju/EFP3AnTRA cACQ== X-Gm-Message-State: APjAAAWiN4LFYeCtgy40kANFvRQOEp1iBEw0ZZxTKFZ/blGdbFaGhhP8 Iv5eTZAVAekj7ABpOejp6V+sY54+ X-Google-Smtp-Source: APXvYqz22Xp4Bha/kHcoUHwURa5oH9/WA3W1Js1+o3th/+U8OIMfM61Tbdg9ifuIT2cMuqk1plKZQA== X-Received: by 2002:a17:902:6a87:: with SMTP id n7mr85600071plk.336.1563989877739; Wed, 24 Jul 2019 10:37:57 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::2:c91a]) by smtp.gmail.com with ESMTPSA id d15sm82710266pjc.8.2019.07.24.10.37.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 10:37:57 -0700 (PDT) Date: Wed, 24 Jul 2019 10:37:55 -0700 From: Tejun Heo To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 2/2] blkcg: don't offline parent blkcg first Message-ID: <20190724173755.GB569612@devbig004.ftw2.facebook.com> References: <20190724173517.GA559934@devbig004.ftw2.facebook.com> <20190724173722.GA569612@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724173722.GA569612@devbig004.ftw2.facebook.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org blkcg->cgwb_refcnt is used to delay blkcg offlining so that blkgs don't get offlined while there are active cgwbs on them. However, it ends up making offlining unordered sometimes causing parents to be offlined before children. Let's fix this by making child blkcgs pin the parents' online states. Note that pin/unpin names are chosen over get/put intentionally because css uses get/put online for something different. Signed-off-by: Tejun Heo --- block/blk-cgroup.c | 16 ++++++++++++++++ include/linux/blk-cgroup.h | 6 +++++- 2 files changed, 21 insertions(+), 1 deletion(-) --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1158,6 +1158,21 @@ unlock: return ret; } +static int blkcg_css_online(struct cgroup_subsys_state *css) +{ + struct blkcg *blkcg = css_to_blkcg(css); + struct blkcg *parent = blkcg_parent(blkcg); + + /* + * blkcg_pin_online() is used to delay blkcg offline so that blkgs + * don't go offline while cgwbs are still active on them. Pin the + * parent so that offline always happens towards the root. + */ + if (parent) + blkcg_pin_online(parent); + return 0; +} + /** * blkcg_init_queue - initialize blkcg part of request queue * @q: request_queue to initialize @@ -1300,6 +1315,7 @@ static void blkcg_exit(struct task_struc struct cgroup_subsys io_cgrp_subsys = { .css_alloc = blkcg_css_alloc, + .css_online = blkcg_css_online, .css_offline = blkcg_css_offline, .css_free = blkcg_css_free, .can_attach = blkcg_can_attach, --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -455,8 +455,12 @@ static inline void blkcg_pin_online(stru */ static inline void blkcg_unpin_online(struct blkcg *blkcg) { - if (refcount_dec_and_test(&blkcg->online_pin)) + do { + if (!refcount_dec_and_test(&blkcg->online_pin)) + break; blkcg_destroy_blkgs(blkcg); + blkcg = blkcg_parent(blkcg); + } while (blkcg); } /**