From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:42242 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751438AbZEEVJs (ORCPT ); Tue, 5 May 2009 17:09:48 -0400 Date: Tue, 5 May 2009 14:05:17 -0700 From: Andrew Morton To: Johannes Weiner Cc: magnus.damm@gmail.com, linux-media@vger.kernel.org, hverkuil@xs4all.nl, lethal@linux-sh.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 1/3] mm: introduce follow_pte() Message-Id: <20090505140517.bef78dd3.akpm@linux-foundation.org> In-Reply-To: <20090505203807.GB2428@cmpxchg.org> References: <20090501181449.GA8912@cmpxchg.org> <1241430874-12667-1-git-send-email-hannes@cmpxchg.org> <20090505122442.6271c7da.akpm@linux-foundation.org> <20090505203807.GB2428@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On Tue, 5 May 2009 22:38:07 +0200 Johannes Weiner wrote: > On Tue, May 05, 2009 at 12:24:42PM -0700, Andrew Morton wrote: > > On Mon, 4 May 2009 11:54:32 +0200 > > Johannes Weiner wrote: > > > > > A generic readonly page table lookup helper to map an address space > > > and an address from it to a pte. > > > > umm, OK. > > > > Is there actually some point to these three patches? If so, what is it? > > Magnus needs to check for physical contiguity of a VMAs backing pages > to support zero-copy exportation of video data to userspace. > > This series implements follow_pfn() so he can walk the VMA backing > pages and ensure their PFNs are in linear order. > > [ This patch can be collapsed with 2/3, I just thought it would be > easier to read the diffs when having them separate. ] > > 1/3 and 2/3: factor out the page table walk from follow_phys() into > follow_pte(). > > 3/3: implement follow_pfn() on top of follow_pte(). So we could bundle these patches with Magnus's patchset, or we could consider these three patches as a cleanup or something. Given that 3/3 introduces an unused function, I'm inclined to sit tight and await Magnus's work.