From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757124AbZEHIvf (ORCPT ); Fri, 8 May 2009 04:51:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751112AbZEHIv1 (ORCPT ); Fri, 8 May 2009 04:51:27 -0400 Received: from an-out-0708.google.com ([209.85.132.251]:47850 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751060AbZEHIvZ convert rfc822-to-8bit (ORCPT ); Fri, 8 May 2009 04:51:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=FhS18sEbpXf0C13YkDRiJMrZQoAn6UKPi741Msxly4iIKlDmagL90MJlCl3x6Ig4E8 06L9vVSvnquNTCcJc4tLaKVWi3S7bWnPFm7AE4gBRJOeywG8ExYVDPFB7dq11ndx76zC GqLtIavQH36ufzode7VDOaC0Zk+BDxhtHxDK8= MIME-Version: 1.0 In-Reply-To: <20090505212139.GA2559@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> <20090505140517.bef78dd3.akpm@linux-foundation.org> <20090505212139.GA2559@cmpxchg.org> Date: Fri, 8 May 2009 17:51:24 +0900 Message-ID: Subject: Re: [patch 1/3] mm: introduce follow_pte() From: Magnus Damm To: Johannes Weiner Cc: Andrew Morton , linux-media@vger.kernel.org, hverkuil@xs4all.nl, lethal@linux-sh.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 6, 2009 at 6:21 AM, Johannes Weiner wrote: > On Tue, May 05, 2009 at 02:05:17PM -0700, Andrew Morton wrote: >> 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. > > Yeah, I didn't see the video guys responding on Magnus' patch yet, so > let's wait for them. > > Magnus, the actual conversion of your code should be trivial, could > you respin it on top of these three patches using follow_pfn() then? So I tested the patches in -mm (1/3, 2/3, 3/3) together with the zero copy patch and everything seems fine. Feel free to add acks from me, least for patch 1/3 and 3/3 - i know too little about the generic case to say anything about 2/3. Acked-by: Magnus Damm I'll send V3 of my zero copy patch in a little while. Thanks a lot for the help! Cheers, / magnus