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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 C03C5C43387 for ; Fri, 21 Dec 2018 17:02:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C09B21903 for ; Fri, 21 Dec 2018 17:02:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545411768; bh=qPl7/9fq8kgrjSFdwZxRRY0jZwzMjoTD/kEnc9Abbig=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=NOqS5HVFOH7ggsAmje3bRc+euqH5RpONsRTSh3HSAY/1Yu4z+37z0+sV/Anf92oY7 0ZunZWtp4uRTicF/g94nu7hrw3G2lCNcSjqu82hT0ntuHYTk2vekXuWRu/zeeYHaRg rV9xaD0ecv/TJrke1V6ZcCJNS2qp2FpY6p6+8/rM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389856AbeLURCr (ORCPT ); Fri, 21 Dec 2018 12:02:47 -0500 Received: from mail-it1-f193.google.com ([209.85.166.193]:40396 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389352AbeLURCr (ORCPT ); Fri, 21 Dec 2018 12:02:47 -0500 Received: by mail-it1-f193.google.com with SMTP id h193so7454219ita.5; Fri, 21 Dec 2018 09:02:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=f2S/HUpNrybDo8EwdKrGzEanCsjWjx4bQPRK1gN9MBY=; b=qDr++mgo3iurYUnuiZGIBuVbI6kaPtL7Et7S52LODMvs7D1rZszQWPbo0BtCST/i4K M6l0t0Cv571hcv83MXM9JXSCShaOsf2l/nH/sD59nT7LWW1g/Gblni4l2VHTLj2+C1cG wTPICcubP8AjIR1Hjo6N7x3vn2tNgH0TuRhnGzahe/MyCJyYK8pf8/ZoZL276nUhyMce vI4n7abfB3/iMR2KFednlvL5/7lTam19AglzN08SQdmcW0AeMPWkRjfjUsYHI9CDkjCu egGlXH1MMj9VEkaUit4eoKY6T0IbzFpD20VfTk/zUWre4OfEfmGk1/f2OMuSzkNQJzI1 aKvQ== X-Gm-Message-State: AA+aEWZvYfx9Uvqu+j+K8pU0UhJeIKmzW2AaQ7Kp+3k2cCIVxPyggYPl n5Z170p8aW3cfD2ic6CrGTo= X-Google-Smtp-Source: AFSGD/V0jbPIWeeyNyEQrPC4vUNzvTGeuMLcZIp7FeGiHEF+vyBhELkWwzJ4F/USoDWFeB1kKZ2Fug== X-Received: by 2002:a24:4709:: with SMTP id t9mr2658005itb.47.1545411766213; Fri, 21 Dec 2018 09:02:46 -0800 (PST) Received: from dennisz-mbp (c-68-59-32-93.hsd1.mn.comcast.net. [68.59.32.93]) by smtp.gmail.com with ESMTPSA id y76sm6966359ita.18.2018.12.21.09.02.45 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Dec 2018 09:02:45 -0800 (PST) Date: Fri, 21 Dec 2018 11:02:43 -0600 From: Dennis Zhou To: Jens Axboe Cc: Dennis Zhou , kernel-team@fb.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] blkcg: add rcu lock to bio_clone_blkg_association() Message-ID: <20181221170243.GA17140@dennisz-mbp> References: <20181221145441.13814-1-dennis@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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! Thanks, Dennis