Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 9 Oct 2019 10:11:52 -0700
From:   "Darrick J. Wong" <darrick.wong@oracle.com>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>,
        linux-xfs@vger.kernel.org, linux-nvdimm@lists.01.org,
        linux-kernel@vger.kernel.org, rgoldwyn@suse.de,
        gujx@cn.fujitsu.com, david@fromorbit.com, qi.fuli@fujitsu.com,
        caoj.fnst@cn.fujitsu.com
Subject: Re: [RFC PATCH 0/7] xfs: add reflink & dedupe support for fsdax.
Message-ID: <20191009171152.GF13108@magnolia>
References: <20190731114935.11030-1-ruansy.fnst@cn.fujitsu.com>
 <20191009063144.GA4300@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20191009063144.GA4300@infradead.org>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Oct 08, 2019 at 11:31:44PM -0700, Christoph Hellwig wrote:
> Btw, I just had a chat with Dan last week on this.  And he pointed out
> that while this series deals with the read/write path issues of 
> reflink on DAX it doesn't deal with the mmap side issue that
> page->mapping and page->index can point back to exactly one file.
> 
> I think we want a few xfstests that reflink a file and then use the
> different links using mmap, as that should blow up pretty reliably.

Hmm, you're right, we don't actually have a test that checks the
behavior of mwriting all copies of a shared block.  Ok, I'll go write
one.

--D