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 C9155C05027 for ; Thu, 9 Feb 2023 14:29:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230432AbjBIO3k (ORCPT ); Thu, 9 Feb 2023 09:29:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230431AbjBIO3Y (ORCPT ); Thu, 9 Feb 2023 09:29:24 -0500 Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::2:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF7E15C89D; Thu, 9 Feb 2023 06:29:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=samba.org; s=42; h=From:Cc:To:Date:Message-ID; bh=3gvgtgLgSW3u20gNVHqhv6UVsa84fGHu0R5hZms47Ng=; b=vt61NckReEUeqnTpd0R9KxOLEI x96E4ZkczjYB62LIb2qijmoleFW85rS+f/TyFBP9IuDVmEsOJ6Wzs6I/LHjM1JAdP/VAwbAfmukSZ lM7jsILULSIb/mSCibXUvb+gYzr6jI1dpOVCCh2HR/bcbsqN72/kQi9eGjmSvgpaWAysHCarFnh0A 8KLbX+MaegIjPKT/hHUIUEJQWsoz551S8hSN3UrHjJ10L+O3XE0QZQOD9DRQMZkOfqAQqAnYoatrG c3Sq8TT/f6koGta7FSjJTCllE3Ve3B00WnaUhP+g9O2mv1caY7u4X8Y9vzxcrmYVBbs7x7MRu3Ju0 ZJS1lIcYUPQRA0koYly5gfaZfB4fWqQZEBPUepvNUYB38lUvML9KPeT4t8bmhMP1hrFIfLaj4faUx TMS8vgaMYOQgu6oZ92Xl24R9q+D6PhYKv628UvzYhZmOmGCFZfRfmgtepoqp9lsXZY1NkmjxbWiso 3FPnDhPXaIkuClZRWKcpnE/m; Received: from [127.0.0.2] (localhost [127.0.0.1]) by hr2.samba.org with esmtpsa (TLS1.3:ECDHE_SECP256R1__ECDSA_SECP256R1_SHA256__CHACHA20_POLY1305:256) (Exim) id 1pQ7vM-00Cp9C-H8; Thu, 09 Feb 2023 14:29:20 +0000 Message-ID: <8476eee4-6227-213f-c6ab-86768d0b58c8@samba.org> Date: Thu, 9 Feb 2023 15:29:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: copy on write for splice() from file to pipe? Content-Language: en-US To: Matthew Wilcox Cc: Linus Torvalds , linux-fsdevel , Linux API Mailing List , io-uring , "linux-kernel@vger.kernel.org" , Al Viro , Samba Technical References: <0cfd9f02-dea7-90e2-e932-c8129b6013c7@samba.org> From: Stefan Metzmacher In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Am 09.02.23 um 15:11 schrieb Matthew Wilcox: > On Thu, Feb 09, 2023 at 02:55:59PM +0100, Stefan Metzmacher wrote: >> Hi Linus and others, >> >> as written in a private mail before, I'm currently trying to >> make use of IORING_OP_SPLICE in order to get zero copy support >> in Samba. > > I have to ask why. In a modern network, isn't all data encrypted? No people use plain connections for performance sensitive workloads and have client and server in isolated vlans. > So you have to encrypt into a different buffer, and then you checksum > that buffer. So it doesn't matter if writes can change the page cache > after you called splice(), you just need to have the data be consistent > so the checksum doesn't change. SMB offers checksuming (signing) only as well as authenticated encryption. For signing only I experimented with splice() in combination with tee(), so that I can checksum the data after reading from tee, while I can still splice() into the socket. For encryption the async_memcpy flag to preadv2 could be usefull if we keep using userspace encryption using gnutls. If using the kernel crypto socket, we could also use splice to add the file data into the crypto functions and the same problem can happen, because some algorithms may encrypt and sign the data in separate steps and it doesn't expect the data to be changed. metze