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Wed, 26 Feb 2020 00:34:18 -0800 (PST) To: Jens Axboe , io-uring References: <1c5f074e-22dd-095a-6be7-730c81eeb1b1@kernel.dk> <82423419-1c14-418e-8085-2d8b902b0a2d@gmail.com> <71add82f-9d25-b879-5fe5-8e2a4eb26877@kernel.dk> <32c9037d-d515-9065-3315-e023edaa4578@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: [PATCH] io_uring: pick up link work on submit reference drop Message-ID: <14cc6bff-565a-c41b-bb96-7b2edad163ce@gmail.com> Date: Wed, 26 Feb 2020 11:33:29 +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: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="VvaYeFCIufJDVPuJsXaZxQyaOuioRvQrG" 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) --VvaYeFCIufJDVPuJsXaZxQyaOuioRvQrG Content-Type: multipart/mixed; boundary="b6uZQqTdcTnP86vZtKvfyxruf9LG9OId0"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring Message-ID: <14cc6bff-565a-c41b-bb96-7b2edad163ce@gmail.com> Subject: Re: [PATCH] io_uring: pick up link work on submit reference drop References: <1c5f074e-22dd-095a-6be7-730c81eeb1b1@kernel.dk> <82423419-1c14-418e-8085-2d8b902b0a2d@gmail.com> <71add82f-9d25-b879-5fe5-8e2a4eb26877@kernel.dk> <32c9037d-d515-9065-3315-e023edaa4578@kernel.dk> In-Reply-To: --b6uZQqTdcTnP86vZtKvfyxruf9LG9OId0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 26/02/2020 01:18, Jens Axboe wrote: > So this found something funky, we really should only be picking up > the next request if we're dropping the final reference to the > request. And io_put_req_find_next() also says that in the comment, > but it always looks it up. That doesn't seem safe at all, I think > this is what it should be: It was weird indeed, it looks good. And now it's safe to do the same in io_wq_submit_work(). Interestingly, this means that passing @nxt into the handlers is useless,= as they won't ever return !=3DNULL, isn't it? I'll prepare the cleanup. >=20 > commit eff5fe974f332c1b86c9bb274627e88b4ecbbc85 > Author: Jens Axboe > Date: Tue Feb 25 13:25:41 2020 -0700 >=20 > io_uring: pick up link work on submit reference drop > =20 > If work completes inline, then we should pick up a dependent link i= tem > in __io_queue_sqe() as well. If we don't do so, we're forced to go = async > with that item, which is suboptimal. > =20 > This also fixes an issue with io_put_req_find_next(), which always = looks > up the next work item. That should only be done if we're dropping t= he > last reference to the request, to prevent multiple lookups of the s= ame > work item. > =20 > Signed-off-by: Jens Axboe >=20 > diff --git a/fs/io_uring.c b/fs/io_uring.c > index ffd9bfa84d86..f79ca494bb56 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -1483,10 +1483,10 @@ static void io_free_req(struct io_kiocb *req) > __attribute__((nonnull)) > static void io_put_req_find_next(struct io_kiocb *req, struct io_kiocb= **nxtptr) > { > - io_req_find_next(req, nxtptr); > - > - if (refcount_dec_and_test(&req->refs)) > + if (refcount_dec_and_test(&req->refs)) { > + io_req_find_next(req, nxtptr); > __io_free_req(req); > + } > } > =20 > static void io_put_req(struct io_kiocb *req) > @@ -4749,7 +4749,7 @@ static void __io_queue_sqe(struct io_kiocb *req, = const struct io_uring_sqe *sqe) > =20 > err: > /* drop submission reference */ > - io_put_req(req); > + io_put_req_find_next(req, &nxt); > =20 > if (linked_timeout) { > if (!ret) >=20 --=20 Pavel Begunkov --b6uZQqTdcTnP86vZtKvfyxruf9LG9OId0-- --VvaYeFCIufJDVPuJsXaZxQyaOuioRvQrG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl5WLVkACgkQWt5b1Glr +6W84A/8CoaGmBoWnopCdSdoXbSWoL0Q2fh1fKXeefiBAxGQHCMv3DrnQ/3OiFUd gLJLzJ2AIgKCpIzBMEty9cXXDTYjAvbhu3rCxK+xkU42CR0pTYhHl6dtm890PIwf sjnssb4D1Dcmy7YSbvc1mDWtHOzzWy2i+ET9ihbOAO79N49sONHHeVJLIlKf5Bly lmYWOhqEsFf8U4nB+fgrCdwKPVNIgoUhyLeGX/QLOZeWZk9xthgntR4NJY0CzSzL jCUrNwL/swb0RIKmkva3zarz1yvQggnOnjp8DN+JiDe5Jo+tftOpyXOfeuNA5RX0 IkRCNjdY5S3BwaWm9BLVhl/n9r/TotAOb7uOOwDZyG4cqtJ6xjWYSk6fRza8g17Y oORsuzr51ZtXVVlwfocqTfCkCTBjJh5P46fq134TYl+l4pVeEuf0xTi/ETMal0OK m+GSQc/UtruF+G62LYur3Mg7AwhMVP7FS2CMBcjhu7EuXn1cY1zix+Pdbs1p8bRS VPZcopYLYyHUSfzyKzbJ8pSA0hq2MG2Tl21Clzaq4yXsXFRBnrT9kss8UMDL7RYe bq7sRT/uUiK1BbvHRh1QIn3TCboB3kHQwX6NzSFyzYV7RoWW7McYhl6/sjciCW3A p9ZoHFHmWhN7LV5HjZB7Jyk2HZRT/jMxqqv+LYG+BMDqtqS07MA= =BKB7 -----END PGP SIGNATURE----- --VvaYeFCIufJDVPuJsXaZxQyaOuioRvQrG--