From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763283AbXIKLRF (ORCPT ); Tue, 11 Sep 2007 07:17:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761006AbXIKLQz (ORCPT ); Tue, 11 Sep 2007 07:16:55 -0400 Received: from brick.kernel.dk ([87.55.233.238]:27272 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754481AbXIKLQy (ORCPT ); Tue, 11 Sep 2007 07:16:54 -0400 Date: Tue, 11 Sep 2007 13:25:27 +0200 From: Jens Axboe To: David Howells Cc: Paul Mundt , Andrew Morton , Greg Ungerer , linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm] splice: Disable vmsplice on nommu. Message-ID: <20070911112526.GK15405@kernel.dk> References: <20070911093510.GA15405@kernel.dk> <20070911082307.GB19495@linux-sh.org> <9949.1189505419@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9949.1189505419@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 11 2007, David Howells wrote: > Jens Axboe wrote: > > > It's a bit of a sledge hammer... Since get_user_pages() appears to work > > on nummu, we can just disable the vmsplice-to-userspace bits and leave > > the (working) vmsplice-from-userspace in place. > > That sounds about right. I don't think you can do the latter without > an MMU, but I may be wrong about what it does. You mean the former? The latter is vmsplice() filling a pipe with user pages, using get_user_pages() to set them up. And that looks like it should work on nommu. The former is vmsplice() using mmap like functionality to map pages into a user vma. Just making sure we agree :-) -- Jens Axboe