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Tue, 21 May 2024 07:06:44 +0000 Message-ID: Date: Tue, 21 May 2024 09:06:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v20 04/12] block: add emulation for copy Content-Language: en-US To: Nitesh Shetty , Jens Axboe , Jonathan Corbet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Keith Busch , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Alexander Viro , Christian Brauner , Jan Kara Cc: martin.petersen@oracle.com, bvanassche@acm.org, david@fromorbit.com, damien.lemoal@opensource.wdc.com, anuj20.g@samsung.com, joshi.k@samsung.com, nitheshshetty@gmail.com, gost.dev@samsung.com, Vincent Fu , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, dm-devel@lists.linux.dev, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org References: <20240520102033.9361-1-nj.shetty@samsung.com> <20240520102033.9361-5-nj.shetty@samsung.com> From: Hannes Reinecke In-Reply-To: <20240520102033.9361-5-nj.shetty@samsung.com> Content-Type: text/plain; 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DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240521_000648_675211_436FE300 X-CRM114-Status: GOOD ( 14.42 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 5/20/24 12:20, Nitesh Shetty wrote: > For the devices which does not support copy, copy emulation is added. > It is required for in-kernel users like fabrics, where file descriptor is > not available and hence they can't use copy_file_range. > Copy-emulation is implemented by reading from source into memory and > writing to the corresponding destination. > At present in kernel user of emulation is fabrics. > > Signed-off-by: Nitesh Shetty > Signed-off-by: Vincent Fu > Signed-off-by: Anuj Gupta > --- > block/blk-lib.c | 223 +++++++++++++++++++++++++++++++++++++++++ > include/linux/blkdev.h | 4 + > 2 files changed, 227 insertions(+) > Again, I'm not sure if we need this. After all, copy offload _is_optional, so we need to be prepared to handle systems where it's not supported. In the end, the caller might decide to do something else entirely; having an in-kernel emulation would defeat that. And with adding an emulation to nullblk we already have an emulation target to try if people will want to start experimenting. So I'd rather not have this but rather let the caller deal with the fact that copy offload is optional. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich