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Tue, 21 Jan 2020 19:12:08 -0800 (PST) Received: from [192.168.43.234] ([109.126.145.157]) by smtp.gmail.com with ESMTPSA id q3sm56270381wrn.33.2020.01.21.19.12.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 19:12:08 -0800 (PST) To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Alexander Viro References: <63119dd6-7668-a7bc-ea24-1db4909762bb@kernel.dk> 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== Subject: Re: [POC RFC 0/3] splice(2) support for io_uring Message-ID: <45f0b63b-e3e7-ba71-d037-9af1db7bbd98@gmail.com> Date: Wed, 22 Jan 2020 06:11:27 +0300 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: <63119dd6-7668-a7bc-ea24-1db4909762bb@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Ir6uQ8kmMcOcEUhuO6HLX6yuWsMNYgzNE" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Ir6uQ8kmMcOcEUhuO6HLX6yuWsMNYgzNE Content-Type: multipart/mixed; boundary="x0tm5hLtcuaId6zzrES9YU9sroBKl5WwS"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Alexander Viro Message-ID: <45f0b63b-e3e7-ba71-d037-9af1db7bbd98@gmail.com> Subject: Re: [POC RFC 0/3] splice(2) support for io_uring References: <63119dd6-7668-a7bc-ea24-1db4909762bb@kernel.dk> In-Reply-To: <63119dd6-7668-a7bc-ea24-1db4909762bb@kernel.dk> --x0tm5hLtcuaId6zzrES9YU9sroBKl5WwS Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 22/01/2020 04:55, Jens Axboe wrote: > On 1/21/20 5:05 PM, Pavel Begunkov wrote: >> It works well for basic cases, but there is still work to be done. E.g= =2E >> it misses @hash_reg_file checks for the second (output) file. Anyway, >> there are some questions I want to discuss: >> >> - why sqe->len is __u32? Splice uses size_t, and I think it's better >> to have something wider (e.g. u64) for fututre use. That's the story >> behind added sqe->splice_len. >=20 > IO operations in Linux generally are INT_MAX, so the u32 is plenty big.= > That's why I chose it. For this specifically, if you look at splice: >=20 > if (unlikely(len > MAX_RW_COUNT)) > len =3D MAX_RW_COUNT; >=20 > so anything larger is truncated anyway. Yeah, I saw this one, but that was rather an argument for the future. It'= s pretty easy to transfer more than 4GB with sg list, but that would be the= case for splice. >=20 >> - it requires 2 fds, and it's painful. Currently file managing is done= >> by common path (e.g. io_req_set_file(), __io_req_aux_free()). I'm >> thinking to make each opcode function handle file grabbing/putting >> themself with some helpers, as it's done in the patch for splice's >> out-file. >> 1. Opcode handler knows, whether it have/needs a file, and thus >> doesn't need extra checks done in common path. >> 2. It will be more consistent with splice. >> Objections? Ideas? >=20 > Sounds reasonable to me, but always easier to judge in patch form :-) >=20 >> - do we need offset pointers with fallback to file->f_pos? Or is it >> enough to have offset value. Jens, I remember you added the first >> option somewhere, could you tell the reasoning? >=20 > I recently added support for -1/cur position, which splice also uses. S= o > you should be fine with that. >=20 I always have been thinking about it as a legacy from old days, and one o= f the problems of posix. It's not hard to count it in the userspace especially = in C++ or high-level languages, and is just another obstacle for having a perfor= mant API. So, I'd rather get rid of it here. But is there any reasons against?= --=20 Pavel Begunkov --x0tm5hLtcuaId6zzrES9YU9sroBKl5WwS-- --Ir6uQ8kmMcOcEUhuO6HLX6yuWsMNYgzNE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl4nvV8ACgkQWt5b1Glr +6VkCA//aCNZp/ksciDSAOD11wim450Ov9jYZXPNn6fFmerie3+01DMZUUE2Zqs0 rsS7FDTQbRECrH9TrVzVFikNjOrHR1p8nXaarZHHt27w8OWajke+pHXDpz3WZo3C rutnN62fK5+P/zYewibsZwSwwXOzZJPwaEXV8ykcUc2IoR2OU+vgVNvggChOChTV QJ8FmsACeZte8CPXjv4wfcJxUc98r4qwCN7rp8//BdUYwQu9QLvCQlbinTeNhO0/ D1vZEFVpEf0bzCj5jQrYDgL/v69CHMiFKHtvxkhe+jVlTgMrogYALeSbFEWhH64w OQZY1iZv1hTACSi8DBAzbN25OgYCLvfvMZck4fQTJfdTbwvPuJ/bPpudyHcNyNvi bpm/Sa08NZWpas6qO5u3jv2hBNBfID7bRBWtXH/5a2v4qcmo/qrQbKVqNasoUTqi L+ZD5yQfq/y9zfm8DyVTbLZEHR8tBh9252A+4asg/Xt6swofMhHQL0nmhB9IEkAf yj3PefJJ5HA46qVoPwl3h0rKo/S/mzMqnwIihHluJjihhX6eMjJXx28zhS1puO12 /v59PNCvSgaiPTqUBiE9wPX+DkYmGWYE98g2Ubx5gohaAQKdFAyRVZ+jbpd9qLUv 2LEUfXzwGuFcFZdOi9Fe4V8WpA74tobjrpBHKcS0g/giKylA7A4= =VszQ -----END PGP SIGNATURE----- --Ir6uQ8kmMcOcEUhuO6HLX6yuWsMNYgzNE--