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,DKIMWL_WL_HIGH, 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 70A22C4361B for ; Tue, 15 Dec 2020 01:43:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0D3D206B2 for ; Tue, 15 Dec 2020 01:43:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730787AbgLOBng (ORCPT ); Mon, 14 Dec 2020 20:43:36 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:60587 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730363AbgLOBnH (ORCPT ); Mon, 14 Dec 2020 20:43:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607996498; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PChAzdtbpi+PB7J87DcIhi+vl5NjETLfLM7SecPuwcY=; b=HIYY4G0QfQNK2paU2qjqY7ECA3c+OG0FwPcb7+gR9iOTYwWp9hbi6xqW5jGswBD9QL3u5y PVa5LiWBHyF5rpV7X3zbz03LwgYiJImBPnu389TFOGFD5WwYDxyLoKfUvAMewbT39i7N+j gOVEZbSGCGex9hyZTatNPzWzFdgSWL0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-335-VMEMQTasPqiCfO3btqz3Kw-1; Mon, 14 Dec 2020 20:41:34 -0500 X-MC-Unique: VMEMQTasPqiCfO3btqz3Kw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A3829180A086; Tue, 15 Dec 2020 01:41:31 +0000 (UTC) Received: from T590 (ovpn-13-7.pek2.redhat.com [10.72.13.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 29ED213470; Tue, 15 Dec 2020 01:41:18 +0000 (UTC) Date: Tue, 15 Dec 2020 09:41:14 +0800 From: Ming Lei To: Pavel Begunkov Cc: 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: <20201215014114.GA1777020@T590> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 15, 2020 at 12:20:19AM +0000, Pavel Begunkov wrote: > Instead of creating a full copy of iter->bvec into bio in direct I/O, > the patchset makes use of the one provided. It changes semantics and > obliges users of asynchronous kiocb to track bvec lifetime, and [1/6] > converts the only place that doesn't. Just think of one corner case: iov_iter(BVEC) may pass bvec table with zero length bvec, which may not be supported by block layer or driver, so this patchset has to address this case first. Please see 7e24969022cb ("block: allow for_each_bvec to support zero len bvec"). thanks, Ming