linux-kernel - Re: [RFC PATCH 0/7] xfs: add reflink & dedupe support for fsdax.

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Message-ID: <20191009171152.GF13108@magnolia>
Date:   Wed, 9 Oct 2019 10:11:52 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Shiyang Ruan <ruansy.fnst@...fujitsu.com>,
        linux-xfs@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org, rgoldwyn@...e.de,
        gujx@...fujitsu.com, david@...morbit.com, qi.fuli@...itsu.com,
        caoj.fnst@...fujitsu.com
Subject: Re: [RFC PATCH 0/7] xfs: add reflink & dedupe support for fsdax.

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