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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 44579C43143 for ; Thu, 13 Sep 2018 17:58:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5403204FD for ; Thu, 13 Sep 2018 17:58:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C5403204FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ZenIV.linux.org.uk 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 S1728109AbeIMXJU (ORCPT ); Thu, 13 Sep 2018 19:09:20 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:39522 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726637AbeIMXJT (ORCPT ); Thu, 13 Sep 2018 19:09:19 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1g0Vt7-0000LX-Cf; Thu, 13 Sep 2018 17:58:45 +0000 Date: Thu, 13 Sep 2018 18:58:45 +0100 From: Al Viro To: David Howells Cc: 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 Message-ID: <20180913175845.GS19965@ZenIV.linux.org.uk> References: <153685389564.14766.11306559824641824935.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153685389564.14766.11306559824641824935.stgit@warthog.procyon.org.uk> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 13, 2018 at 04:51:35PM +0100, David Howells wrote: > > Hi Al, > > Here's a set of patches that adds two new iov_iter types and then makes AFS > use them to do I/O. The iov_iter changes are: > > (1) Separate the type from the direction in the iov_iter struct and > provide accessor functions to wrap type checking. > > (2) Renumber the type constants to be contiguous small unsigned integers, > starting from 0 and then use switch-statements rather than if-else > chains using bit-testing. > > Note that the compiler can optimise this better by using CMP rather > than AND/TEST, say, as comparing integers requires fewer CMP > instructions or can use jump tables. > > (3) Change iov_offset from size_t to loff_t. This allows iov_offset to be > then used as a byte offset with ITER_MAPPING and allows 4GiB and larger > reads and writes to be proposed. > > This makes no difference on a 64-bit system, but does make a 32-bit > compilation a bit larger. > > (4) Add an ITER_MAPPING iterator type. This provides an iterator that > directly accesses an address_space, and assumes that the target pages > are in some way locked (eg. PG_lock or PG_writeback). > > (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. Hmm... I'll take a look in about an hour (need to finish the sodding tty-ioctl stuff first), will post review then. Sorry, I remember seeing it posted several weeks ago, slipped through the cracks then ;-/