From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from haymarket.ed.ac.uk (haymarket.ed.ac.uk [129.215.128.53])
	by kvack.org (8.8.7/8.8.7) with ESMTP id FAA26937
	for <linux-mm@kvack.org>; Wed, 1 Jul 1998 05:23:40 -0400
Date: Wed, 1 Jul 1998 10:12:40 +0100
Message-Id: <199807010912.KAA00789@dax.dcs.ed.ac.uk>
From: "Stephen C. Tweedie" <sct@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Subject: Re: (reiserfs) Re: More on Re: (reiserfs) Reiserfs and ext2fs (was Re: (reiserfs) Sum Benchmarks (these look typical?))
In-Reply-To: <m1n2au77ck.fsf@flinx.npwt.net>
References: <Pine.HPP.3.96.980617035608.29950A-100000@ixion.honeywell.com>
	<199806221138.MAA00852@dax.dcs.ed.ac.uk>
	<358F4FBE.821B333C@ricochet.net>
	<m11zsgrvnf.fsf@flinx.npwt.net>
	<199806241154.MAA03544@dax.dcs.ed.ac.uk>
	<m11zse6ecw.fsf@flinx.npwt.net>
	<199806251100.MAA00835@dax.dcs.ed.ac.uk>
	<m1emwcf97d.fsf@flinx.npwt.net>
	<199806291035.LAA00733@dax.dcs.ed.ac.uk>
	<m1u354dlna.fsf@flinx.npwt.net>
	<199806301610.RAA00957@dax.dcs.ed.ac.uk>
	<m1n2au77ck.fsf@flinx.npwt.net>
Sender: owner-linux-mm@kvack.org
To: "Eric W. Biederman" <ebiederm+eric@npwt.net>
Cc: "Stephen C. Tweedie" <sct@redhat.com>, Hans Reiser <reiser@ricochet.net>, Shawn Leas <sleas@ixion.honeywell.com>, Reiserfs <reiserfs@devlinux.com>, Ken Tetrick <ktetrick@ixion.honeywell.com>, linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>

Hi,

On 30 Jun 1998 19:17:15 -0500, ebiederm+eric@npwt.net (Eric
W. Biederman) said:

> When either I trace through the code, or a hardware guy convinces me,
> that it is safe to both write to a page, and do DMA from a page
> simultaneously I'll believe it.

Read the source code!  We already do this.  If one process or thread
msync()s a mapped file, its dirty pages get written to disk,
independently of any other processes on the same or other CPUs which
may still have the pages mapped and may still be writing to them.  We
don't unmap pages for write; we just mark them non-dirty around all
ptes.

--Stephen