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

[Darrick J. Wong]

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