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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A95DFC433DB for ; Tue, 9 Feb 2021 06:13:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3617864EB8 for ; Tue, 9 Feb 2021 06:13:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3617864EB8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8E86D6B0005; Tue, 9 Feb 2021 01:13:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 899B76B006C; Tue, 9 Feb 2021 01:13:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7AF9D6B006E; Tue, 9 Feb 2021 01:13:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0159.hostedemail.com [216.40.44.159]) by kanga.kvack.org (Postfix) with ESMTP id 64E436B0005 for ; Tue, 9 Feb 2021 01:13:54 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 2D1A5824805A for ; Tue, 9 Feb 2021 06:13:54 +0000 (UTC) X-FDA: 77797713588.22.turn84_3c03ecb27605 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id D7AA4180D96BF for ; Tue, 9 Feb 2021 06:13:53 +0000 (UTC) X-HE-Tag: turn84_3c03ecb27605 X-Filterd-Recvd-Size: 2955 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf25.hostedemail.com (Postfix) with ESMTP for ; Tue, 9 Feb 2021 06:13:53 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 52CFD64EB4; Tue, 9 Feb 2021 06:13:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612851232; bh=vXvZjO+dJ8YWmqHgcCh15Ljh8Qtw2DaVGWOZH6EHT0k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2Po3kesrKpij7luyyByApUUHGyuySlg8ir7gDdTWQMwPAG2oVcqY7PkOYOyyZkdHR 9UCuHmQUNEgynRm8VV3Y8+52dGbPgvuzT4YLztJfyDhpku52eLhKzsg0h3UyV7E2DJ mJv3z2j3BLNRH9lPryeE/m71TG8Z7rOffQwEK4Ik= Date: Tue, 9 Feb 2021 07:13:48 +0100 From: Greg KH To: John Hubbard Cc: Minchan Kim , Andrew Morton , linux-mm , LKML , surenb@google.com, joaodias@google.com, willy@infradead.org Subject: Re: [PATCH v2] mm: cma: support sysfs Message-ID: References: <20210208180142.2765456-1-minchan@kernel.org> <43cd6fc4-5bc5-50ec-0252-ffe09afd68ea@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43cd6fc4-5bc5-50ec-0252-ffe09afd68ea@nvidia.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000042, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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? thanks, greg k-h