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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC5A5C433E6 for ; Tue, 22 Dec 2020 14:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 946B823130 for ; Tue, 22 Dec 2020 14:11:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727028AbgLVOL4 (ORCPT ); Tue, 22 Dec 2020 09:11:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726979AbgLVOL4 (ORCPT ); Tue, 22 Dec 2020 09:11:56 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98D93C0613D6; Tue, 22 Dec 2020 06:11:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=T+iXOP0M1Q96GjQwN7A0jbcvtdBz8ylHUEIBZyFxI8I=; b=PeK+jxcEN9Ejy/YT3iuu9bqQFV 7MYpiQ6MVIDoC07jo6Sb1KyxsiLNp/bafk92FKVYRNJk2pwjwrZ9Flk6GSvkhS7h+O3IfD9Ei2thK B98TTdovOFeDCsH6r0ocT67368f7x0o+JIL0zp1TBG8JY+IzqJQBgN2xUx7a1wVQK7BZNnnDibsCd Qg98YScZ5H1Gl5f8SF8aD4kVU8TGakW14RHIJCiQ4jhS8/xMI15DOpnymEbhFkIje4sxCcWRbsKO9 z33BDSDf6kKnTtAqGIJKVE/ZYH4s/x/W7vkbPvN9389IvWQikHwQNG9zv+6ujEMaJC7vxtwuhmsbm 5PoND+Qg==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kriNc-00048z-VF; Tue, 22 Dec 2020 14:11:13 +0000 Date: Tue, 22 Dec 2020 14:11:12 +0000 From: Christoph Hellwig To: Pavel Begunkov Cc: Ming Lei , linux-block@vger.kernel.org, Jens Axboe , Christoph Hellwig , Matthew Wilcox , Johannes Weiner , Alexander Viro , "Darrick J . Wong" , "Martin K . Petersen" , Jonathan Corbet , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v1 0/6] no-copy bvec Message-ID: <20201222141112.GE13079@infradead.org> References: <20201215014114.GA1777020@T590> <103235c1-e7d0-0b55-65d0-013d1a09304e@gmail.com> <20201215120357.GA1798021@T590> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Tue, Dec 15, 2020 at 02:05:35PM +0000, Pavel Begunkov wrote: > > You may find clue from the following link: > > > > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2262077.html > > Thanks for the link! > > Al, you mentioned "Zero-length segments are not disallowed", do you have > a strong opinion on that? Apart from already diverged behaviour from the > block layer and getting in the way of this series, without it we'd also be > able to remove some extra ifs, e.g. in iterate_bvec() I'd prefer not to support zero-length ITER_BVEC and catching them early, as the block layer can't deal with them either. From a quick look at iter_file_splice_write it should be pretty trivial to fix there, although we'll need to audit other callers as well (even if I don't expect them to submit this degenerate case).