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

[Christoph Hellwig]

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.