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=-8.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3C21EC433E6 for ; Tue, 9 Feb 2021 06:27:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C063864EB9 for ; Tue, 9 Feb 2021 06:27:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C063864EB9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1C0316B006E; Tue, 9 Feb 2021 01:27:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1710A6B0070; Tue, 9 Feb 2021 01:27:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0864A6B0071; Tue, 9 Feb 2021 01:27:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0135.hostedemail.com [216.40.44.135]) by kanga.kvack.org (Postfix) with ESMTP id E6FD06B006E for ; Tue, 9 Feb 2021 01:27:27 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9AD3E18327DE3 for ; Tue, 9 Feb 2021 06:27:27 +0000 (UTC) X-FDA: 77797747734.03.nut46_290679127605 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 75A3428A4E9 for ; Tue, 9 Feb 2021 06:27:27 +0000 (UTC) X-HE-Tag: nut46_290679127605 X-Filterd-Recvd-Size: 4347 Received: from hqnvemgate26.nvidia.com (hqnvemgate26.nvidia.com [216.228.121.65]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Tue, 9 Feb 2021 06:27:26 +0000 (UTC) Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, AES256-SHA) id ; Mon, 08 Feb 2021 22:27:25 -0800 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 9 Feb 2021 06:27:24 +0000 Received: from [10.2.50.67] (172.20.145.6) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 9 Feb 2021 06:27:24 +0000 Subject: Re: [PATCH v2] mm: cma: support sysfs To: Greg KH CC: Minchan Kim , Andrew Morton , linux-mm , LKML , , , References: <20210208180142.2765456-1-minchan@kernel.org> <43cd6fc4-5bc5-50ec-0252-ffe09afd68ea@nvidia.com> From: John Hubbard Message-ID: <7cc229f4-609c-71dd-9361-063ef1bf7c73@nvidia.com> Date: Mon, 8 Feb 2021 22:27:24 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:85.0) Gecko/20100101 Thunderbird/85.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To DRHQMAIL107.nvidia.com (10.27.9.16) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1612852045; bh=X0aIckYSF9wc/TONr7/whXV7WyEI3S3ZRv/IkzFkkzw=; h=Subject:To:CC:References:From:Message-ID:Date:User-Agent: MIME-Version:In-Reply-To:Content-Type:Content-Language: Content-Transfer-Encoding:X-Originating-IP:X-ClientProxiedBy; b=KRzOE4v0vMuGPLYxhNQn2OXAeSmuSgrbctCSIrCIKYpZd2sc41twl/ibfplX4GxTO TzMElz0s24BeSyr43v3+hgD9C3s81a9Lv/iHYMhLUYTaRth/8+iWd9IjLQNC+ZTc33 bvl7ZxZQoH+STN6yc8HYgKPdEG2otJ3DXdP4DqhTp5hu6ig0/jdhyCD+ucg5FB7+Y8 +kheXPXiU453iApKBzQ2wN4g4qMAM4QimxGYbLYFd5VYV1QHJmRvldWyQS4WySJ+j5 fB5pIBKtY9cqSX0e1nDF8hXLZVEyazk8lQmWCBHul7/NM0VxmDWAILvC5SfcT22lGm yEI007isKxtMA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/8/21 10:13 PM, Greg KH wrote: > On Mon, Feb 08, 2021 at 05:57:17PM -0800, John Hubbard wrote: >> On 2/8/21 3:36 PM, Minchan Kim wrote: >> ... >>>>> char name[CMA_MAX_NAME]; >>>>> +#ifdef CONFIG_CMA_SYSFS >>>>> + struct cma_stat *stat; >>>> >>>> This should not be a pointer. By making it a pointer, you've added a bunch of pointless >>>> extra code to the implementation. >>> >>> Originally, I went with the object lifetime with struct cma as you >>> suggested to make code simple. However, Greg KH wanted to have >>> release for kobj_type since it is consistent with other kboject >>> handling. >> >> Are you talking about the kobj in your new struct cma_stat? That seems >> like circular logic if so. I'm guessing Greg just wanted kobj methods >> to be used *if* you are dealing with kobjects. That's a narrower point. >> >> I can't imagine that he would have insisted on having additional >> allocations just so that kobj freeing methods could be used. :) > > Um, yes, I was :) > > You can not add a kobject to a structure and then somehow think you can > just ignore the reference counting issues involved. If a kobject is > part of a structure then the kobject is responsible for controling the > lifespan of the memory, nothing else can be. > > So by making the kobject dynamic, you properly handle that memory > lifespan of the object, instead of having to worry about the lifespan of > the larger object (which the original patch was not doing.) > > Does that make sense? > That part makes sense, yes, thanks. The part that I'm trying to straighten out is, why was kobject even added to the struct cma_stat in the first place? Why not just leave .stat as a static member variable, without a kobject in it, and done? thanks, -- John Hubbard NVIDIA