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Wed, 30 Jun 2021 09:14:13 +0000 Received: from [172.27.12.24] (172.20.187.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 30 Jun 2021 09:14:08 +0000 Subject: Re: [PATCH rdma-next v1 1/2] lib/scatterlist: Fix wrong update of orig_nents To: Christoph Hellwig , Leon Romanovsky CC: Doug Ledford , Jason Gunthorpe , Dennis Dalessandro , , , "Mike Marciniszyn" , Yishai Hadas , Zhu Yanjun References: From: Maor Gottlieb Message-ID: <2134e949-0569-c495-cb0b-f0324c5920df@nvidia.com> Date: Wed, 30 Jun 2021 12:14:04 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [172.20.187.5] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: df31ab85-3b3e-40cd-053f-08d93ba76d9b X-MS-TrafficTypeDiagnostic: MWHPR1201MB2526: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6108; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2021 09:14:13.3069 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: df31ab85-3b3e-40cd-053f-08d93ba76d9b 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: CO1NAM11FT032.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1201MB2526 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/30/2021 10:16 AM, Christoph Hellwig wrote: > On Wed, Jun 30, 2021 at 10:02:11AM +0300, Leon Romanovsky wrote: >> Another possible solution is to change __sg_alloc_table()/__sg_alloc_table_from_pages >> to return total_nents and expect from the users to store it internally and pass >> it later to the __sg_free_table(). >> >> Something like that. > Yes, that sounds pretty reasonable. OK. So we have two options 1. Add another argument (output) to __sg_alloc_table_from_pages and __sg_free_table.     The thing is that __sg_free_table gets free_fn as argument while __sg_alloc_table_from_pages doesn't get alloc function. Users will pass NULL as free_fn and scatterlist internally will use sg_kfree. 2. Have dedicated functions to the appending allocations - sg_alloc_table_from_pages_append and sg_free_table_append. With this approach users that use __sg_alloc_table_from_pages not for appending allocation don't need to maintain the new argument. Christoph, what do you prefer? do you see a better option?