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 0660FC43387 for ; Fri, 21 Dec 2018 15:26:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C8C7F21917 for ; Fri, 21 Dec 2018 15:26:07 +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="dbdhsJmG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730462AbeLUP0G (ORCPT ); Fri, 21 Dec 2018 10:26:06 -0500 Received: from mail-io1-f67.google.com ([209.85.166.67]:34769 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729898AbeLUP0G (ORCPT ); Fri, 21 Dec 2018 10:26:06 -0500 Received: by mail-io1-f67.google.com with SMTP id l22so730712ioh.1 for ; Fri, 21 Dec 2018 07:26:05 -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=/MOIU7hCsgrd/rUq3ud9ch+X2/+EbU8ewisM4YIgtGY=; b=dbdhsJmGsOSB+AA63/Q6jCU3vqxbAlLr63XWlj390FEt8OOeuM8ZmgoHB9RvePlScG VCowq9+tpRgDDO1iJVDD643fvYoqdq6iVvwwElexMCjsSp8f8eYI5Un57Jgrr1izJqbS eO+ZoyGAjGIBk8XE3ZfS+DsOiFW2VkOcDXFSWGCA26RPrXbFZi2HLP15TXbj578glYcL j+XqEX6bz+cccsuhirxecTJIRP7QvDp/NGjFO+VssqVRkDvEUkso2Qy+3X9qKez3lvd1 pB1jOso2VDpT1GLcb9c81ge/FimYGArb3SyvrJxVE4MUfLVtgWxPENFGAEJdTt45+FqJ uCpw== 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=/MOIU7hCsgrd/rUq3ud9ch+X2/+EbU8ewisM4YIgtGY=; b=FjhVOnnTOWVoRm0U3dtysU+ceqziWLowBSNRNY04SKek0UbIUBLwFbGXbIOn5d7XKz 3sjW0/VGw0KDz1G/1wQX8cuMRI7ksq7f00s7RkjkPxh1dgYYe5klE7dOg2ecr6eK84FE 8Z9CkiRLo1TlLgtodAMh15WZ2bKFw3H7NQmBqPYATsoVjzOY+4qhnHzByCTddO0uv+mu p0MpkRlHmcRfPM01HTPzmoxd82zaOf0+2AXGNvntVJTE0dtkATpYHL1jsnyH5MYcIOvV Vh7zvUi8zWHplibkup+iK+6v/IHsixlA0x/nNs7sh+jBZ2ZuVRiJVGxydV1EckNn+SJn feyg== X-Gm-Message-State: AJcUuke59FRShrthJa+bm1owJSPg7dkIZ6N3Mg382cnjii5huMBVU03t z6Vd3F0EbHDvZbejDLf3lGzW+qrK3p8NrQ== X-Google-Smtp-Source: ALg8bN7eb4DsG7be1azb0kU80jXkAxew9Aky/32eIZBv1A2iAPECCzCmdxuWsAcCaQgH4XWgIH03fg== X-Received: by 2002:a6b:3bc8:: with SMTP id i191mr1974794ioa.23.1545405964947; Fri, 21 Dec 2018 07:26:04 -0800 (PST) Received: from [192.168.1.56] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id p19sm9205231itp.13.2018.12.21.07.26.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Dec 2018 07:26:03 -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> From: Jens Axboe Message-ID: Date: Fri, 21 Dec 2018 08:26:02 -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: <20181221145441.13814-1-dennis@kernel.org> 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 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. -- Jens Axboe