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Sun, 1 Aug 2021 18:49:22 +0000 Subject: Re: [Resend PATCH v4] scsi: target: tcmu: Add new feature KEEP_BUF To: Bodo Stroesser , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, "Martin K. Petersen" References: <20210713175021.20103-1-bostroesser@gmail.com> From: Mike Christie Message-ID: <1ace896d-5a3f-4f20-5b79-1907805097d4@oracle.com> Date: Sun, 1 Aug 2021 13:49:20 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 In-Reply-To: <20210713175021.20103-1-bostroesser@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DM5PR12CA0059.namprd12.prod.outlook.com (2603:10b6:3:103::21) To BYAPR10MB3573.namprd10.prod.outlook.com (2603:10b6:a03:11e::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [20.15.0.204] (73.88.28.6) by DM5PR12CA0059.namprd12.prod.outlook.com (2603:10b6:3:103::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4373.20 via Frontend Transport; Sun, 1 Aug 2021 18:49:22 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8f0ae849-a1f5-460f-cd10-08d9551d13c9 X-MS-TrafficTypeDiagnostic: BYAPR10MB3128: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6430; 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In that case userspace has to > copy data before sending completion, because cmd completion also > implicitly releases the data buffer in data area. > > The new feature KEEP_BUF allows userspace to optionally keep the > buffer after completion by setting new bit TCMU_UFLAG_KEEP_BUF in > tcmu_cmd_entry_hdr->uflags. In that case buffer has to be released > explicitly by writing the cmd_id to new action item free_kept_buf. > > All kept buffers are released during reset_ring and if userspace > closes uio device (tcmu_release). > > Signed-off-by: Bodo Stroesser Reviewed-by: Mike Christie