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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 8BCDBF81820 for ; Thu, 13 Sep 2018 17:35:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5A9F2156F for ; Thu, 13 Sep 2018 16:18:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B5A9F2156F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728417AbeIMV2h (ORCPT ); Thu, 13 Sep 2018 17:28:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37728 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727413AbeIMV2h (ORCPT ); Thu, 13 Sep 2018 17:28:37 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id CD450C058CB7; Thu, 13 Sep 2018 16:18:25 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-123-84.rdu2.redhat.com [10.10.123.84]) by smtp.corp.redhat.com (Postfix) with ESMTP id A398B600D1; Thu, 13 Sep 2018 16:18:24 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20180913161054.GB11574@bombadil.infradead.org> References: <20180913161054.GB11574@bombadil.infradead.org> <153685389564.14766.11306559824641824935.stgit@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 00/10] iov_iter: Add new iters and use with AFS MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <17351.1536855503.1@warthog.procyon.org.uk> Date: Thu, 13 Sep 2018 17:18:23 +0100 Message-ID: <17352.1536855503@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 13 Sep 2018 16:18:25 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Matthew Wilcox wrote: > > (5) Add an ITER_DISCARD iterator type. This provides an iterator that > > simply discards anything written to it. It cannot be used as a data > > source. > > May I suggest an ITER_ZERO iterator type instead? It acts like /dev/zero; > writes are discarded (as you have here) and reads return zeroes. > I've wanted such a thing in the past, but got distracted away from > that project. I thought about that, but the zero-filling is not as easy to implement as the discard side - plus I don't have any use case to test it with. Do you have a use case in mind? David