From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH 3/3] RFC: dax: dax_prepare_freeze
Date: Tue, 24 Mar 2015 09:40:47 +1100
Message-ID: <20150323224047.GQ28621@dastard>
References: <55100B78.501@plexistor.com>
 <55100D10.6090902@plexistor.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Jan Kara <jack@suse.cz>, Hugh Dickins <hughd@google.com>,
	Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org,
	linux-nvdimm <linux-nvdimm@ml01.01.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Eryu Guan <eguan@redhat.com>
To: Boaz Harrosh <boaz@plexistor.com>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
Received: from ipmail06.adl6.internode.on.net ([150.101.137.145]:43494 "EHLO
	ipmail06.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK)
	by vger.kernel.org with ESMTP id S1753129AbbCWWku (ORCPT
	<rfc822;linux-fsdevel@vger.kernel.org>);
	Mon, 23 Mar 2015 18:40:50 -0400
Content-Disposition: inline
In-Reply-To: <55100D10.6090902@plexistor.com>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Mon, Mar 23, 2015 at 02:54:40PM +0200, Boaz Harrosh wrote:
> From: Boaz Harrosh <boaz@plexistor.com>
> 
> When freezing an FS, we must write protect all IS_DAX()
> inodes that have an mmap mapping on an inode. Otherwise
> application will be able to modify previously faulted-in
> file pages.

All you need to do is lock out page faults once the page is clean;
that's what the sb_start_pagefault() calls are for in the page fault
path - they catch write faults and block them until the filesystem
is unfrozen. Hence I'm not sure why this would be necessary if you
are catching write faults in .pfn_mkwrite....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com