From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 182CFC761AF for ; Wed, 29 Mar 2023 07:00:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229448AbjC2HAD (ORCPT ); Wed, 29 Mar 2023 03:00:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229550AbjC2HAC (ORCPT ); Wed, 29 Mar 2023 03:00:02 -0400 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 30D5C268B; Wed, 29 Mar 2023 00:00:00 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0Vevp.P8_1680073195; Received: from 30.97.56.166(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0Vevp.P8_1680073195) by smtp.aliyun-inc.com; Wed, 29 Mar 2023 14:59:56 +0800 Message-ID: <8a30ac76-dbee-e785-a6fc-1a752af9b18f@linux.alibaba.com> Date: Wed, 29 Mar 2023 14:59:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH V3 00/16] io_uring/ublk: add IORING_OP_FUSED_CMD Content-Language: en-US To: Ming Lei , Pavel Begunkov Cc: Jens Axboe , io-uring@vger.kernel.org, linux-block@vger.kernel.org, Miklos Szeredi , Xiaoguang Wang , Bernd Schubert References: <20230314125727.1731233-1-ming.lei@redhat.com> <3971d43f-601f-635f-5a30-df7e647f6659@kernel.dk> <4f8161e7-5229-45c4-1bb2-b86d87e22a16@gmail.com> <8b227cf3-6ad1-59ad-e13b-a46381958a4c@gmail.com> From: Ziyang Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 2023/3/28 21:01, Ming Lei wrote: [...] >> >> >>> So re-using splice for this purpose is still bad not mention splice >>> can't support writeable spliced page. >>> >>> Wiring device io buffer with context registered buffer table looks like >>> another approach, however: >>> >>> 1) two uring command OPs for registering/unregistering this buffer in io fast >>> path has to be added since only userspace can know when buffer(reference) >>> isn't needed >> >> Yes, that's a good point. Registration replaces fuse master cmd, so it's >> one extra request for unregister, which might be fine. > > Unfortunately I don't think this way is good, the problem is that buffer > only has physical pages, and doesn't have userspace mapping, so why bother > to export it to userspace? > > As I replied to Ziyang, the current fused command can be extended to > this way easily, but I don't know why we need to use the buffer registration, > given userspace can't read/write the buffer, and fused command can cover > it just fine. > Hi Ming, I have replied to you in another email.