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=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 6CBFAC433F4 for ; Fri, 31 Aug 2018 01:54:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B19B2082C for ; Fri, 31 Aug 2018 01:54:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="L4pGlUrx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B19B2082C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727669AbeHaF7b (ORCPT ); Fri, 31 Aug 2018 01:59:31 -0400 Received: from mail-yw1-f67.google.com ([209.85.161.67]:47055 "EHLO mail-yw1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727643AbeHaF7a (ORCPT ); Fri, 31 Aug 2018 01:59:30 -0400 Received: by mail-yw1-f67.google.com with SMTP id j131-v6so4510424ywc.13; Thu, 30 Aug 2018 18:54:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=Tu/AriW7HdBy3hcsN7f/g+VUfGV9GCz/UgAHKU8KDmw=; b=L4pGlUrxrEzZMR8p1KPpJpEOBv6PlROFKL19Z+Co1NyRMzzYpT36JXKdJyhaLS6bO3 GjOcIAShcjSmBMHCgcDOSkMrpO62nQJMShLwmrHQ7ouXVbbw6l0oIJzvPAE+gHQq/wkM Dn99dyAfJduPXusYjkX1zeusfVZNzAJcvK0t7a+35zhE6Iuo5/HbQvfkdtVeftf0N1ZW gWxWHleWSoXoyJuOxZf52ULtbNJmt+Mw+PqleW6lwhcVPszJwSjX/eBdythvLZkwFtsM Vo1jzvg3TjmGI6JgfmER06xvh8Z6BDFY2cVoK0WO0ehRxQYSILfhN0FzHvF139fmZXup eI3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=Tu/AriW7HdBy3hcsN7f/g+VUfGV9GCz/UgAHKU8KDmw=; b=CG/tQIUNdo/1vbRW6takbqz3Z4pzjNKDmCsBtBsfjuBVwSrE5iUL0AmHvbp/hksYpH J0jO/HM3HTAxNWbx0r9VDreK1ak2GJu/uCemlEsBiynSacwca1iP6L/yrqpx1kNcOck5 NHF2td0ugEX49IaHr9qpC2XY4n2NyKNz+djo5GiUlZUQFWIPPhiyPJzGDVvV4J1F4h+J fJSE68MEkZ3/UG0cyvomUoOU/8ODu0s8kLhvIANXX84uABIjCBrllTUp0UAg38G14vvw FoURL+u6rZbkuGxxTny7KV8nErU2C3cpimTk8ttvPP1HEWsvwTa40QJ40T+XUlgolBAF eIwQ== X-Gm-Message-State: APzg51BQgQLOZcUkeXDmDqhjYe69via8kZo2vZCLMrTLbJJrxN2Bkf6A cxEoDs8uEvPwDJGV5d3df4uddj8mAw8= X-Google-Smtp-Source: ANB0VdZ7bUqWT+6ztM8v88xQtbpUyudcSJ1Wfs5NqK55EvOnKSrxzSSEg79wfC3FVOyaV4z1G0ge0A== X-Received: by 2002:a0d:d48b:: with SMTP id w133-v6mr7595156ywd.374.1535680467225; Thu, 30 Aug 2018 18:54:27 -0700 (PDT) Received: from dennisz-mbp.thefacebook.com ([199.201.65.129]) by smtp.gmail.com with ESMTPSA id j70-v6sm3274084ywb.69.2018.08.30.18.54.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Aug 2018 18:54:26 -0700 (PDT) From: Dennis Zhou To: Jens Axboe , Tejun Heo , Johannes Weiner , Josef Bacik Cc: kernel-team@fb.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, "Dennis Zhou (Facebook)" Subject: [PATCH 13/15] blkcg: change blkg reference counting to use percpu_ref Date: Thu, 30 Aug 2018 21:53:54 -0400 Message-Id: <20180831015356.69796-14-dennisszhou@gmail.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20180831015356.69796-1-dennisszhou@gmail.com> References: <20180831015356.69796-1-dennisszhou@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Dennis Zhou (Facebook)" Now that every bio is associated with a blkg, this puts the use of blkg_get, blkg_try_get, and blkg_put on the hot path. This switches over the refcnt in blkg to use percpu_ref. Signed-off-by: Dennis Zhou --- block/blk-cgroup.c | 56 +++++++++++++++++++++----------------- include/linux/blk-cgroup.h | 14 +++------- 2 files changed, 35 insertions(+), 35 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index f678cd555814..bbea4b44bd8f 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -84,6 +84,30 @@ static void blkg_free(struct blkcg_gq *blkg) kfree(blkg); } +/* + * A group is RCU protected, but having an rcu lock does not mean that one + * can access all the fields of blkg and assume these are valid. For + * example, don't try to follow throtl_data and request queue links. + * + * Having a reference to blkg under an rcu allows accesses to only values + * local to groups like group stats and group rate limits. + */ +static void __blkg_release(struct percpu_ref *ref) +{ + struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt); + + percpu_ref_exit(&blkg->refcnt); + + /* release the blkcg and parent blkg refs this blkg has been holding */ + css_put(&blkg->blkcg->css); + if (blkg->parent) + blkg_put(blkg->parent); + + wb_congested_put(blkg->wb_congested); + + blkg_free(blkg); +} + /** * blkg_alloc - allocate a blkg * @blkcg: block cgroup the new blkg is associated with @@ -110,7 +134,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, blkg->q = q; INIT_LIST_HEAD(&blkg->q_node); blkg->blkcg = blkcg; - atomic_set(&blkg->refcnt, 1); /* root blkg uses @q->root_rl, init rl only for !root blkgs */ if (blkcg != &blkcg_root) { @@ -217,6 +240,10 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, blkg_get(blkg->parent); } + ret = percpu_ref_init(&blkg->refcnt, __blkg_release, 0, GFP_KERNEL); + if (ret) + goto err_cancel_ref; + /* invoke per-policy init */ for (i = 0; i < BLKCG_MAX_POLS; i++) { struct blkcg_policy *pol = blkcg_policy[i]; @@ -249,6 +276,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, blkg_put(blkg); return ERR_PTR(ret); +err_cancel_ref: + percpu_ref_exit(&blkg->refcnt); err_put_congested: wb_congested_put(wb_congested); err_put_css: @@ -378,7 +407,7 @@ static void blkg_destroy(struct blkcg_gq *blkg) * Put the reference taken at the time of creation so that when all * queues are gone, group can be destroyed. */ - blkg_put(blkg); + percpu_ref_kill(&blkg->refcnt); } /** @@ -405,29 +434,6 @@ static void blkg_destroy_all(struct request_queue *q) q->root_rl.blkg = NULL; } -/* - * A group is RCU protected, but having an rcu lock does not mean that one - * can access all the fields of blkg and assume these are valid. For - * example, don't try to follow throtl_data and request queue links. - * - * Having a reference to blkg under an rcu allows accesses to only values - * local to groups like group stats and group rate limits. - */ -void __blkg_release_rcu(struct rcu_head *rcu_head) -{ - struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head); - - /* release the blkcg and parent blkg refs this blkg has been holding */ - css_put(&blkg->blkcg->css); - if (blkg->parent) - blkg_put(blkg->parent); - - wb_congested_put(blkg->wb_congested); - - blkg_free(blkg); -} -EXPORT_SYMBOL_GPL(__blkg_release_rcu); - /* * The next function used by blk_queue_for_each_rl(). It's a bit tricky * because the root blkg uses @q->root_rl instead of its own rl. diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index 97cb82029b18..b60d063fb0d7 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -126,7 +126,7 @@ struct blkcg_gq { struct request_list rl; /* reference count */ - atomic_t refcnt; + struct percpu_ref refcnt; /* is this blkg online? protected by both blkcg and q locks */ bool online; @@ -455,8 +455,7 @@ static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen) */ static inline void blkg_get(struct blkcg_gq *blkg) { - WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0); - atomic_inc(&blkg->refcnt); + percpu_ref_get(&blkg->refcnt); } /** @@ -468,23 +467,18 @@ static inline void blkg_get(struct blkcg_gq *blkg) */ static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg) { - if (atomic_inc_not_zero(&blkg->refcnt)) + if (percpu_ref_tryget(&blkg->refcnt)) return blkg; return NULL; } - -void __blkg_release_rcu(struct rcu_head *rcu); - /** * blkg_put - put a blkg reference * @blkg: blkg to put */ static inline void blkg_put(struct blkcg_gq *blkg) { - WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0); - if (atomic_dec_and_test(&blkg->refcnt)) - call_rcu(&blkg->rcu_head, __blkg_release_rcu); + percpu_ref_put(&blkg->refcnt); } /** -- 2.17.1