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=-2.7 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 46B2BC43143 for ; Thu, 6 Sep 2018 21:11:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA93D20844 for ; Thu, 6 Sep 2018 21:11:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QmBKY0Nd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA93D20844 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 S1728392AbeIGBsT (ORCPT ); Thu, 6 Sep 2018 21:48:19 -0400 Received: from mail-yb1-f193.google.com ([209.85.219.193]:37876 "EHLO mail-yb1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728114AbeIGBsS (ORCPT ); Thu, 6 Sep 2018 21:48:18 -0400 Received: by mail-yb1-f193.google.com with SMTP id f145-v6so4692918ybg.4; Thu, 06 Sep 2018 14:11:01 -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=GsrSo3YYCaTDgNImQTvjTcK+H+77PIQv1o+ghf7Ahqs=; b=QmBKY0NdXoF0ARRChPUg4DTo5DQZXZvHuL/dbTpZ2cJUeglw3itd1ywwtni2pmAHzU iA0O/kaqWA+ohPhxgl+U1HjPWhVdjQYSyu895+JVCcqD9AeE4+N/uayJcfsB9wYA5be4 Il9ln3ho2OI4glGXLIbDvSfjoZfjjcc9qO09qTAZFwgEevO2mOHkfmp7QbkylSEwhClg tYfUVmsQwRQcwiHn6aI3CTyiBkoxCMqZ3alYv6FT5wsMJEM59lVkBDgP/NOa9j4P9SI+ LPh0SXWA8LL39N8HPlsl3ND9wmcZWCN6N+Hb3+oTi2SRwtLmcVTIVbrQmLMtG6A2tBei ywzA== 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=GsrSo3YYCaTDgNImQTvjTcK+H+77PIQv1o+ghf7Ahqs=; b=WAUWuxvqov7WAEMfclGSL/vO6iHQ2jbHc1+4a/TRRZA0CTbrLvqjXi86LzbGsAh6bp 6o9ChWmWXcTkY9F2EJKoA8spzhCfc+dppUg8wBdJovafvy7amDxKoZPDF8kIfq5hIEfC JEbWEsMaIth7kmUn0pED0sY0cjgjQqfcvJbJuja8b4ZqkuKZMK6w2YczGavnElF2ZeMe /HT5e/sGa862pmxQINAlNX2+sCFiD9YWKAQMGgxnvWu0eL+cODBgIUdZ8aszkKITGUr6 FaOejpQVLzNKQUFNLMdOC7F2oTxCfRADCzHyoanUpCZytLg/fGOXFFA2TkCX9IomKtdl P/SA== X-Gm-Message-State: APzg51AiybNghQptrpNm2IVOymH6vZ0pkC0DMqrf5DDEvTiFMil3fx7s +1NX1REDTYqKcDXvfyzZmeo= X-Google-Smtp-Source: ANB0VdZ22ia+d7E9FmG28mSALWWj8FELmZA0qkq/ZnDtnMxcapLaIzBAh2S4K+axKU6h3XGUcc9tYw== X-Received: by 2002:a25:ac8c:: with SMTP id x12-v6mr2611813ybi.513.1536268260766; Thu, 06 Sep 2018 14:11:00 -0700 (PDT) Received: from dennisz-mbp.thefacebook.com ([199.201.65.129]) by smtp.gmail.com with ESMTPSA id u67-v6sm2032802ywa.56.2018.09.06.14.10.59 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Sep 2018 14:11:00 -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 03/12] blkcg: convert blkg_lookup_create to find closest blkg Date: Thu, 6 Sep 2018 17:10:36 -0400 Message-Id: <20180906211045.29055-4-dennisszhou@gmail.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20180906211045.29055-1-dennisszhou@gmail.com> References: <20180906211045.29055-1-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)" There are several scenarios where blkg_lookup_create can fail. Examples include the blkcg dying, request_queue is dying, or simply being OOM. At the end of the day, most handle this by simply falling back to the q->root_blkg and calling it a day. This patch implements the notion of closest blkg. During blkg_lookup_create, if it fails to create, return the closest blkg found or the q->root_blkg. blkg_try_get_closest is introduced and used during association so a bio is always attached to a blkg. Signed-off-by: Dennis Zhou --- block/bio.c | 4 +--- block/blk-cgroup.c | 22 +++++++++++++++------- include/linux/blk-cgroup.h | 14 ++++++++++++++ 3 files changed, 30 insertions(+), 10 deletions(-) diff --git a/block/bio.c b/block/bio.c index 91c6b1458454..cd947ad4cf08 100644 --- a/block/bio.c +++ b/block/bio.c @@ -2021,9 +2021,7 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) { if (unlikely(bio->bi_blkg)) return -EBUSY; - if (!blkg_try_get(blkg)) - return -ENODEV; - bio->bi_blkg = blkg; + bio->bi_blkg = blkg_try_get_closest(blkg); return 0; } diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index cd0d97bed83d..9f8aba29b7c1 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -268,9 +268,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, * that all non-root blkg's have access to the parent blkg. This function * should be called under RCU read lock and @q->queue_lock. * - * Returns pointer to the looked up or created blkg on success, ERR_PTR() - * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not - * dead and bypassing, returns ERR_PTR(-EBUSY). + * Returns the blkg or the closest blkg if blkg_create fails as it walks + * down from root. */ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, struct request_queue *q) @@ -285,7 +284,7 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, * we shouldn't allow anything to go through for a bypassing queue. */ if (unlikely(blk_queue_bypass(q))) - return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY); + return q->root_blkg; blkg = __blkg_lookup(blkcg, q, true); if (blkg) @@ -298,14 +297,23 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, while (true) { struct blkcg *pos = blkcg; struct blkcg *parent = blkcg_parent(blkcg); - - while (parent && !__blkg_lookup(parent, q, false)) { + struct blkcg_gq *ret_blkg = NULL; + + while (parent) { + blkg = __blkg_lookup(parent, q, false); + if (blkg) { + /* remember closest blkg */ + ret_blkg = blkg; + break; + } pos = parent; parent = blkcg_parent(parent); } blkg = blkg_create(pos, q, NULL); - if (pos == blkcg || IS_ERR(blkg)) + if (IS_ERR(blkg)) + return ret_blkg ?: q->root_blkg; + if (pos == blkcg) return blkg; } } diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index cc0f238530f6..1fbff1bbb651 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -549,6 +549,20 @@ static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg) return NULL; } +/** + * blkg_try_get_closest - try and get a blkg ref on the closet blkg + * @blkg: blkg to get + * + * This walks up the blkg tree to find the closest non-dying blkg and returns + * the blkg that it did association with as it may not be the passed in blkg. + */ +static inline struct blkcg_gq *blkg_try_get_closest(struct blkcg_gq *blkg) +{ + while (!atomic_inc_not_zero(&blkg->refcnt)) + blkg = blkg->parent; + + return blkg; +} void __blkg_release_rcu(struct rcu_head *rcu); -- 2.17.1