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Wed, 24 Mar 2021 22:23:11 +0000 Received: from [10.2.88.242] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 24 Mar 2021 22:23:10 +0000 Subject: Re: [PATCH v7] mm: cma: support sysfs To: Dmitry Osipenko , Minchan Kim , Andrew Morton CC: linux-mm , LKML , , , , , Colin Ian King References: <20210324205503.2132082-1-minchan@kernel.org> <65840bfd-4471-7c8d-ce71-c4705baf3bfe@gmail.com> <0ac4d495-eece-fb71-d334-a46e069b0c35@nvidia.com> <0396987d-1331-51a0-83f4-0c49dd3e150c@gmail.com> From: John Hubbard Message-ID: Date: Wed, 24 Mar 2021 15:23:09 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <0396987d-1331-51a0-83f4-0c49dd3e150c@gmail.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 9dc2b6e3-81ca-4e91-e778-08d8ef1368a5 X-MS-TrafficTypeDiagnostic: MN2PR12MB4205: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6790; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Mar 2021 22:23:11.0396 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9dc2b6e3-81ca-4e91-e778-08d8ef1368a5 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT056.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4205 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/24/21 3:11 PM, Dmitry Osipenko wrote: > 25.03.2021 01:01, John Hubbard пишет: >> On 3/24/21 2:31 PM, Dmitry Osipenko wrote: >>> ... >>>> +#include >>>> + >>>> +struct cma_kobject { >>>> +    struct cma *cma; >>>> +    struct kobject kobj; >>> >>> If you'll place the kobj as the first member of the struct, then >>> container_of will be a no-op. >>> >> >> However, *this does not matter*. Let's not get carried away. If >> container_of() ends up as a compile-time addition of +8, instead >> of +0, there is not going to be a visible effect in the world. >> Or do you have some perf data to the contrary? >> >> Sometimes these kinds of things matter. But other times, they are >> just pointless to fret about, and this is once such case. > > Performance is out of question here, my main point is about maintaining In that case, there is even less reason to harass people about the order of members of a struct. > a good coding style. Otherwise there is no point in not embedding kobj > into cma struct as well, IMO. We really don't need to worry about the order of members in a struct, from a "coding style" point of view. It is a solid step too far. Sorry if that sounds a little too direct. But this review has tended to go quite too far into nitpicks that are normally left as-is, and I've merely picked one that is particularly questionable. I realize that other coding communities have their own standards. Here, I'm explaining what I have observed about linux-mm and linux-kernel, which needs to be respected. thanks, -- John Hubbard NVIDIA