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Tue, 4 May 2021 00:26:58 +0000 Received: from [10.2.50.162] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 4 May 2021 00:26:58 +0000 Subject: Re: [PATCH 13/16] nvme-pci: Convert to using dma_map_sg_p2pdma for p2pdma pages To: Logan Gunthorpe , , , , , , CC: Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?UTF-8?Q?Christian_K=c3=b6nig?= , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy References: <20210408170123.8788-1-logang@deltatee.com> <20210408170123.8788-14-logang@deltatee.com> <78a165e1-657b-c284-d31a-adc8c9ded55d@nvidia.com> <4ad9c1d9-ec2a-1fe1-c5d9-19d2053da912@deltatee.com> From: John Hubbard Message-ID: <92116e67-7388-aa31-cff3-71a7da82a731@nvidia.com> Date: Mon, 3 May 2021 17:26:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <4ad9c1d9-ec2a-1fe1-c5d9-19d2053da912@deltatee.com> 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 HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 167a9abe-a59e-4567-3a56-08d90e93544b X-MS-TrafficTypeDiagnostic: CH2PR12MB3767: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:5797; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(396003)(39860400002)(346002)(136003)(376002)(36840700001)(46966006)(53546011)(478600001)(16526019)(82740400003)(54906003)(186003)(36756003)(70586007)(36860700001)(36906005)(2616005)(4744005)(31686004)(356005)(70206006)(316002)(47076005)(82310400003)(336012)(426003)(2906002)(8936002)(31696002)(8676002)(7636003)(5660300002)(16576012)(110136005)(86362001)(4326008)(26005)(7416002)(43740500002)(2101003);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 May 2021 00:26:58.5694 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 167a9abe-a59e-4567-3a56-08d90e93544b 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: DM6NAM11FT037.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB3767 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 5/3/21 10:19 AM, Logan Gunthorpe wrote: ... >>> + nr_mapped = dma_map_sg_p2pdma_attrs(dev->dev, iod->sg, iod->nents, >>> + rq_dma_dir(req), DMA_ATTR_NO_WARN); >>> + if (nr_mapped < 0) { >>> + if (nr_mapped != -ENOMEM) >>> + ret = BLK_STS_TARGET; >>> goto out_free_sg; >>> + } >> >> But now the "nr_mapped == 0" case is no longer doing an early out_free_sg. >> Is that OK? > > dma_map_sg_p2pdma_attrs() never returns zero. It will return -ENOMEM in > the same situation and results in the same goto out_free_sg. > OK...that's true, it doesn't return zero. A comment or WARN or something might be nice, to show that the zero case hasn't been overlooked. It's true that the dma_map_sg_p2pdma_attrs() documentation sort of says that (although not quite out loud). thanks, -- John Hubbard NVIDIA