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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, MAILING_LIST_MULTI,SPF_PASS 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 E008CC43612 for ; Fri, 21 Dec 2018 17:03:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE08921903 for ; Fri, 21 Dec 2018 17:03:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="fTYEw8ta" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389901AbeLURDM (ORCPT ); Fri, 21 Dec 2018 12:03:12 -0500 Received: from mail-it1-f195.google.com ([209.85.166.195]:50202 "EHLO mail-it1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730879AbeLURDM (ORCPT ); Fri, 21 Dec 2018 12:03:12 -0500 Received: by mail-it1-f195.google.com with SMTP id z7so7809770iti.0 for ; Fri, 21 Dec 2018 09:03:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Hf5qZoOeGEo9ju4n7h/sv9g8Q8I5xApPDnIUfUGruv0=; b=fTYEw8taRKtOBatcK/jmE/yizYPBUjdGSjQInlMmVcXEuyiKDKYYLsBl3WgGK16JeS yMRZIQs3O8Smncp3zJzLi88+kNqCm/S4qlL4tEWoGNOpcgwJDXub83YOQOMjBYOmVGDu ni6o3r4w2bHsiXzAXzfbyC+CynGiGu31bMa7Ih8kkcGg/hYQFgeJh9GAa1YKMVT+50iM aS+8brYsAoSMbZzikfObGIYrDymaltYy+uE1K54k3+SEKqmFwqIx7PZh8aCfqzN9AWQW 9xJVpKQfzVBQ6n7LRzoLXN1EyyueuJ+/J+XT1/caKywnk02dchzhUfb8tWmdfYt3X8+x XR2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Hf5qZoOeGEo9ju4n7h/sv9g8Q8I5xApPDnIUfUGruv0=; b=YaBIsrA2MnFPGjMWX6DIq5xht6DCLvk4OVeW3z2aNEZjNaZhvD1QCad+zV/rzJHV8x hfxclEWx8/cEdabqhnWtfLzqW1oMl4xFJgCMpUeFFDWeD6L25lUuYSqGkfimvd/5ZDpD MLOBE6lJpUPXbfscexODQ2eIx4x/z+cnbbyXiwb78PQkL5UkkTE7KQ+1Rn5ieJvOFUgz 2gKEYkE80qHdM3aYfR0j7PMur/0THDvwOKs50QPn9eHS9M84DeZWj1n2KDixdlvqCply C0BongHfW417qyYYKAeyptcKOQw2VCdsZg9sHX4bEjUmIj91lJS6x5rw2YJTdDgCszbf Tfqg== X-Gm-Message-State: AA+aEWZPYSeI5BeZE/xo5TP5Ae17wnqZor/z4wgULRCxUGu/dmXsO3Ys eX0sJMWcvQXnzCkDIEKzfNj32+wCQWm+6w== X-Google-Smtp-Source: AFSGD/XUWF+XpqsQlMTCsV0UOEGMObT2VAkzPKQF9isNZR7GMMQAXgb7/nWBzug+qSePGrfiJwX+VA== X-Received: by 2002:a02:97fd:: with SMTP id v58mr2157219jaj.115.1545411791057; Fri, 21 Dec 2018 09:03:11 -0800 (PST) Received: from [192.168.1.56] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id 195sm6430371itm.2.2018.12.21.09.03.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Dec 2018 09:03:10 -0800 (PST) Subject: Re: [PATCH] blkcg: add rcu lock to bio_clone_blkg_association() To: Dennis Zhou Cc: kernel-team@fb.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20181221145441.13814-1-dennis@kernel.org> <20181221170243.GA17140@dennisz-mbp> From: Jens Axboe Message-ID: Date: Fri, 21 Dec 2018 10:03:08 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181221170243.GA17140@dennisz-mbp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/21/18 10:02 AM, Dennis Zhou wrote: > On Fri, Dec 21, 2018 at 08:26:02AM -0700, Jens Axboe wrote: >> On 12/21/18 7:54 AM, Dennis Zhou wrote: >>> I cleaned up blkg_tryget_closest() to require rcu_read_lock() earlier. >>> However, this was a subtle case too which clearly was too subtle for me. >>> The idea was the src bio should be holding a ref to the blkg so rcu >>> wasn't technically needed. If it doesn't hold a ref, it should be %NULL >>> and the blkg->parent pointers are unused. >>> >>> This adds the appropriate read lock in bio_clone_blkg_association(). >> >> Shall I just fold this with the previous? I staged it in a >> later-in-merge-cycle branch, so that's not an issue to amend. >> > > Yeah that would be great! Done -- Jens Axboe