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Wed, 27 Jan 2021 07:46:28 -0800 (PST) Subject: Re: [RFC PATCH 0/4] Asynchronous passthrough ioctl To: Kanchan Joshi , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me References: <20210127150029.13766-1-joshi.k@samsung.com> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <489691ce-3b1e-30ce-9f72-d32389e33901@gmail.com> Date: Wed, 27 Jan 2021 15:42:46 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20210127150029.13766-1-joshi.k@samsung.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210127_104633_116384_ECF71B64 X-CRM114-Status: GOOD ( 24.73 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: selvakuma.s1@samsung.com, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, javier.gonz@samsung.com, nj.shetty@samsung.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 27/01/2021 15:00, Kanchan Joshi wrote: > This RFC patchset adds asynchronous ioctl capability for NVMe devices. > Purpose of RFC is to get the feedback and optimize the path. > > At the uppermost io-uring layer, a new opcode IORING_OP_IOCTL_PT is > presented to user-space applications. Like regular-ioctl, it takes > ioctl opcode and an optional argument (ioctl-specific input/output > parameter). Unlike regular-ioctl, it is made to skip the block-layer > and reach directly to the underlying driver (nvme in the case of this > patchset). This path between io-uring and nvme is via a newly > introduced block-device operation "async_ioctl". This operation > expects io-uring to supply a callback function which can be used to > report completion at later stage. > > For a regular ioctl, NVMe driver submits the command to the device and > the submitter (task) is made to wait until completion arrives. For > async-ioctl, completion is decoupled from submission. Submitter goes > back to its business without waiting for nvme-completion. When > nvme-completion arrives, it informs io-uring via the registered > completion-handler. But some ioctls may require updating certain > ioctl-specific fields which can be accessed only in context of the > submitter task. For that reason, NVMe driver uses task-work infra for > that ioctl-specific update. Since task-work is not exported, it cannot > be referenced when nvme is compiled as a module. Therefore, one of the > patch exports task-work API. > > Here goes example of usage (pseudo-code). > Actual nvme-cli source, modified to issue all ioctls via this opcode > is present at- > https://github.com/joshkan/nvme-cli/commit/a008a733f24ab5593e7874cfbc69ee04e88068c5 see https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-fops Looks like good time to bring that branch/discussion back > > With regular ioctl- > int nvme_submit_passthru(int fd, unsigned long ioctl_cmd, > struct nvme_passthru_cmd *cmd) > { > return ioctl(fd, ioctl_cmd, cmd); > } > > With uring passthru ioctl- > int nvme_submit_passthru(int fd, unsigned long ioctl_cmd, > struct nvme_passthru_cmd *cmd) > { > return uring_ioctl(fd, ioctl_cmd, cmd); > } > int uring_ioctl(int fd, unsinged long cmd, u64 arg) > { > sqe = io_uring_get_sqe(ring); > > /* prepare sqe */ > sqe->fd = fd; > sqe->opcode = IORING_OP_IOCTL_PT; > sqe->ioctl_cmd = cmd; > sqe->ioctl_arg = arg; > > /* submit sqe */ > io_uring_submit(ring); > > /* reap completion and obtain result */ > io_uring_wait_cqe(ring, &cqe); > printf("ioctl result =%d\n", cqe->res) > } > > Kanchan Joshi (4): > block: introduce async ioctl operation > kernel: export task_work_add > nvme: add async ioctl support > io_uring: add async passthrough ioctl support > > drivers/nvme/host/core.c | 347 +++++++++++++++++++++++++++------- > fs/io_uring.c | 77 ++++++++ > include/linux/blkdev.h | 12 ++ > include/uapi/linux/io_uring.h | 7 +- > kernel/task_work.c | 2 +- > 5 files changed, 376 insertions(+), 69 deletions(-) > -- Pavel Begunkov _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme