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Wed, 09 Dec 2020 03:57:40 -0800 (PST) To: Christoph Hellwig Cc: Jens Axboe , Alexander Viro , linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Ming Lei References: <20201209083645.GB21968@infradead.org> <20201209090646.GA28832@infradead.org> 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 1/2] iov: introduce ITER_BVEC_FLAG_FIXED Message-ID: Date: Wed, 9 Dec 2020 11:54:24 +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: <20201209090646.GA28832@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/12/2020 09:06, Christoph Hellwig wrote: > On Wed, Dec 09, 2020 at 08:36:45AM +0000, Christoph Hellwig wrote: >> This is making the iter type even more of a mess than it already is. >> I think we at least need placeholders for 0/1 here and an explicit >> flags namespace, preferably after the types. >> >> Then again I'd much prefer if we didn't even add the flag or at best >> just add it for a short-term transition and move everyone over to the >> new scheme. Otherwise the amount of different interfaces and supporting >> code keeps exploding. At least the flag can be ignored. Anyway sounds good to me. I'll take your patch below to the series, thanks! > > Note that the only other callers that use iov_iter_bvec and asynchronous > read/write are loop, target and nvme-target, so this should actually > be pretty simple. Out of these only target needs something like this > trivial change to keep the bvec available over the duration of the I/O, > the other two should be fine already: > > --- > From 581a8eabbb1759e3dcfee4b1d2e419f814a8cb80 Mon Sep 17 00:00:00 2001 > From: Christoph Hellwig > Date: Wed, 9 Dec 2020 10:05:04 +0100 > Subject: target/file: allocate the bvec array as part of struct target_core_file_cmd > > This saves one memory allocation, and ensures the bvecs aren't freed > before the AIO completion. This will allow the lower level code to be > optimized so that it can avoid allocating another bvec array. > > Signed-off-by: Christoph Hellwig > --- > drivers/target/target_core_file.c | 20 ++++++-------------- > 1 file changed, 6 insertions(+), 14 deletions(-) > > diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c > index 7143d03f0e027e..ed0c39a1f7c649 100644 > --- a/drivers/target/target_core_file.c > +++ b/drivers/target/target_core_file.c > @@ -241,6 +241,7 @@ struct target_core_file_cmd { > unsigned long len; > struct se_cmd *cmd; > struct kiocb iocb; > + struct bio_vec bvecs[]; > }; > > static void cmd_rw_aio_complete(struct kiocb *iocb, long ret, long ret2) > @@ -268,29 +269,22 @@ fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents, > struct target_core_file_cmd *aio_cmd; > struct iov_iter iter = {}; > struct scatterlist *sg; > - struct bio_vec *bvec; > ssize_t len = 0; > int ret = 0, i; > > - aio_cmd = kmalloc(sizeof(struct target_core_file_cmd), GFP_KERNEL); > + aio_cmd = kmalloc(struct_size(aio_cmd, bvecs, sgl_nents), GFP_KERNEL); > if (!aio_cmd) > return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; > > - bvec = kcalloc(sgl_nents, sizeof(struct bio_vec), GFP_KERNEL); > - if (!bvec) { > - kfree(aio_cmd); > - return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; > - } > - > for_each_sg(sgl, sg, sgl_nents, i) { > - bvec[i].bv_page = sg_page(sg); > - bvec[i].bv_len = sg->length; > - bvec[i].bv_offset = sg->offset; > + aio_cmd->bvecs[i].bv_page = sg_page(sg); > + aio_cmd->bvecs[i].bv_len = sg->length; > + aio_cmd->bvecs[i].bv_offset = sg->offset; > > len += sg->length; > } > > - iov_iter_bvec(&iter, is_write, bvec, sgl_nents, len); > + iov_iter_bvec(&iter, is_write, aio_cmd->bvecs, sgl_nents, len); > > aio_cmd->cmd = cmd; > aio_cmd->len = len; > @@ -307,8 +301,6 @@ fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents, > else > ret = call_read_iter(file, &aio_cmd->iocb, &iter); > > - kfree(bvec); > - > if (ret != -EIOCBQUEUED) > cmd_rw_aio_complete(&aio_cmd->iocb, ret, 0); > > -- Pavel Begunkov