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Tue, 17 Dec 2019 10:13:10 -0800 (PST) Received: from [192.168.43.142] ([109.126.149.134]) by smtp.gmail.com with ESMTPSA id i5sm3794900wml.31.2019.12.17.10.13.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Dec 2019 10:13:10 -0800 (PST) Subject: Re: [PATCH 3/3] io_uring: move *queue_link_head() from common path To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <17f7900c-385f-0dfa-11bf-af99d080f894@gmail.com> <76917820-052d-9597-133d-424fee3edade@kernel.dk> <5d4af2f6-26a2-b241-5131-3a0155cbbf22@kernel.dk> <3b5100a7-2922-a9f2-e4e2-76252318959d@gmail.com> <7edd6631-326c-ac9c-7c5b-fa4bab3932d3@kernel.dk> <4f3f9b65-6e9f-b650-65b8-1e0844321697@gmail.com> <69cb864c-9fa9-2d5a-7b75-f72633cb32f5@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== Message-ID: Date: Tue, 17 Dec 2019 21:12:44 +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: <69cb864c-9fa9-2d5a-7b75-f72633cb32f5@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zVeI1w3A3FylcW2gBXjb1YYgTgAqxJLK8" 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) --zVeI1w3A3FylcW2gBXjb1YYgTgAqxJLK8 Content-Type: multipart/mixed; boundary="DaddbFasQNuVPg5p4mHw2bbG8IePXXq4A"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: Subject: Re: [PATCH 3/3] io_uring: move *queue_link_head() from common path References: <17f7900c-385f-0dfa-11bf-af99d080f894@gmail.com> <76917820-052d-9597-133d-424fee3edade@kernel.dk> <5d4af2f6-26a2-b241-5131-3a0155cbbf22@kernel.dk> <3b5100a7-2922-a9f2-e4e2-76252318959d@gmail.com> <7edd6631-326c-ac9c-7c5b-fa4bab3932d3@kernel.dk> <4f3f9b65-6e9f-b650-65b8-1e0844321697@gmail.com> <69cb864c-9fa9-2d5a-7b75-f72633cb32f5@kernel.dk> In-Reply-To: <69cb864c-9fa9-2d5a-7b75-f72633cb32f5@kernel.dk> --DaddbFasQNuVPg5p4mHw2bbG8IePXXq4A Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 17/12/2019 21:07, Jens Axboe wrote: > On 12/17/19 11:05 AM, Pavel Begunkov wrote: >> On 17/12/2019 21:01, Jens Axboe wrote: >>> On 12/17/19 10:52 AM, Pavel Begunkov wrote: >>>> On 17/12/2019 20:37, Jens Axboe wrote: >>>>> On 12/17/19 9:45 AM, Jens Axboe wrote: >>>>>> On 12/16/19 4:38 PM, Pavel Begunkov wrote: >>>>>>> On 17/12/2019 02:22, Pavel Begunkov wrote: >>>>>>>> - } else if (req->sqe->flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)= ) { >>>>>>>> + >>>>>>>> + /* last request of a link, enqueue the link */ >>>>>>>> + if (!(sqe_flags & IOSQE_IO_LINK)) { >>>>>>> >>>>>>> This looks suspicious (as well as in the current revision). Retur= ning back >>>>>>> to my questions a few days ago can sqe->flags have IOSQE_IO_HARDL= INK, but not >>>>>>> IOSQE_IO_LINK? I don't find any check. >>>>>>> >>>>>>> In other words, should it be as follows? >>>>>>> !(sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) >>>>>> >>>>>> Yeah, I think that should check for both. I'm fine with either app= roach >>>>>> in general: >>>>>> >>>>>> - IOSQE_IO_HARDLINK must have IOSQE_IO_LINK set >>>>>> >>>>>> or >>>>>> >>>>>> - IOSQE_IO_HARDLINK implies IOSQE_IO_LINK >>>>>> >>>>>> Seems like the former is easier to verify in terms of functionalit= y, >>>>>> since we can rest easy if we check this early and -EINVAL if that = isn't >>>>>> the case. >>>>>> >>>>>> What do you think? >>>>> >>>>> If you agree, want to send in a patch for that for 5.5? Then I can = respin >>>>> for-5.6/io_uring on top of that, and we can apply your cleanups the= re. >>>>> >>>> Yes, that's the idea. Already got a patch, if you haven't done it ye= t. >>> >>> I haven't. >>> >>>> Just was thinking, whether to add a check for not setting both flags= >>>> at the same moment in the "imply" case. Would give us 1 state in 2 b= its >>>> for future use. >>> >>> Not sure I follow what you're saying here, can you elaborate? >>> >> >> Sure >> >> #define IOSQE_IO_LINK (1U << 2) /* links next sqe */ >> #define IOSQE_IO_HARDLINK (1U << 3) /* like LINK, but stronger */ >> >> That's 2 consequent bits, so 4 states: >> 0,0 -> not a link >> 1,0 -> common link >> 0,1 -> hard link >> 1,1 -> reserved, space for another link-quirk type >> >> But that would require additional check, i.e. >> >> if (flags&(LINK|HARDLINK) =3D=3D (LINK|HARDLINK)) ... >=20 > Ah, I see. In terms of usability, I think it makes more sense to have >=20 > IOSQE_LINK | IOSQE_HARDLINK >=20 > be the same as just IOSQE_LINK. It would be nice to retain that for Probably, you meant it to be the same as __IOSQE_HARDLINK__ > something else, but I think it'll be more confusing to users. >=20 Yeah, and it's easier for something like: sqe->flags |=3D IOSQE_LINK; [some code] if (timer_or_whatever()) sqe->flags |=3D IOSQE_HARDLINK; --=20 Pavel Begunkov --DaddbFasQNuVPg5p4mHw2bbG8IePXXq4A-- --zVeI1w3A3FylcW2gBXjb1YYgTgAqxJLK8 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl35GpwACgkQWt5b1Glr +6Xm5w/+Py5sgWj31AS3rhNGDS6qyJCS4ZrimKu4/WjxTk09JYgO78ndf3/8RnUi MyKeoaNRWExRVsCfWJ6Nowr93f5ztP8Dyag1v57lKdlbYfh6ERnS9mhbAcTl907i r32U7obrmNtgFeMWphsDCwfHwclwX4YM25n58/TMtIVLU4BIVmVMTCtz7NUID0q8 Kn4naoNkPD+qoA70N9QLeC1+6RACzpG7xDS4ABrtWXA+rFkGO8y8HTOUE0U4xu/l U86zLc6FDS7ElotKEVKyce7XL56Dq732H6opifajcnZTyECeRByce/C42NogM7LB eDDij8okKZMY3RwzRtWxts9mkMosGAu7IqmhuOVto7owbWbHOZbF7BqbFySqrGM5 EHf3EAYw9SZwY1h0aUdvHPTNh/Tu+rGwF9OoI5wi6LO7d2Vz5kZSIJvbRinBJBAV g8VOHSeG9kB+/Yd7FKWSddl5Fcdtf5lpV8QlXglJs2a0aNwk2Q70//jJmrYWyZIy DWuuK8dmlJ/BxUUvMPYngft7lnkGNBUxvFEgb2UImHaxTktgC38YJ9M1IA+xohNb TiaxTdKLGvtHeo8sXnMAfAiz5eBSZfENBcCS3Emu4q3IHRadDzO+oGiprMODqsNW LesI3G6wagevoSTkyEWalLamtHe4+9/+0pA+vvqbWLdRORgJ37M= =FGRQ -----END PGP SIGNATURE----- --zVeI1w3A3FylcW2gBXjb1YYgTgAqxJLK8--