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 49630C433F5 for ; Mon, 28 Feb 2022 10:47:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234889AbiB1KsC (ORCPT ); Mon, 28 Feb 2022 05:48:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229565AbiB1Kr7 (ORCPT ); Mon, 28 Feb 2022 05:47:59 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 109285B888; Mon, 28 Feb 2022 02:47:19 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id BBBA1B80FF2; Mon, 28 Feb 2022 10:47:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26BB0C340E7; Mon, 28 Feb 2022 10:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646045236; bh=wKsdoTANU5hpG2zlBt0hwyF+7+quOlTjzA0JHxNClnY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RRObxfQNLSdZIiAH3BZhaD4LIww+/AHsaRBHjOolKzZF4/eGh5zIjLWvg0q8H6yT8 pA3jOoXTWA7jwLEhPde/cTtTNsVc2PnWb68hpE1E3mzdYrP6YrbRPY8k4ShYmP5/qh rVKF8m5KZDO7o0iyU0r3t7CtUoDT/zPuXAfWSYRU= Date: Mon, 28 Feb 2022 11:47:13 +0100 From: Greg KH To: Xiaoguang Wang Cc: Bodo Stroesser , Guixin Liu , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-kernel@vger.kernel.org, xlpang@linux.alibaba.com Subject: Re: [PATCH 2/2] scsi:target:tcmu: reduce once copy by using uio ioctl Message-ID: References: <1645064962-94123-1-git-send-email-kanie@linux.alibaba.com> <1645064962-94123-2-git-send-email-kanie@linux.alibaba.com> <4aef53b1-3e0f-92eb-4bd3-cdc4cd301866@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4aef53b1-3e0f-92eb-4bd3-cdc4cd301866@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 28, 2022 at 04:52:52PM +0800, Xiaoguang Wang wrote: > > hi Bodo, > > > Liu, > > > > generally I like ideas to speed up tcmu. > > > > OTOH, since Andy Grover implemented tcmu based on uio device, we are > > restricted to what uio offers. With today's knowledge I think we would > > not use the uio device in tcmu again, but switching away from uio now > > would break existing userspace SW. > Yeah, it will have much work if deciding to switch away from uio. > I came up with a hacky or crazy idea :) what about we create a new file > in tcmu_open() by anon_inode_getfile_secure(), and export this fd by > tcmu mail box, we can do ioctl() on this new file, then uio framework > won't be touched... No new ioctls please. That is creating a new user/kernel api that you must support for the next 20+ years. Please do not do that. thanks, greg k-h