Re: [PATCH v5 9/9] btrfs: btrfs_copy_file_range() only supports reflinks

On Wed, Sep 30, 2015 at 01:26:53PM -0400, Anna Schumaker wrote:

Reject copies that don't have the COPY_FR_REFLINK flag set.

I think a reflink actually is a perfectly valid copy, and I don't buy
the duplicate arguments in earlier threads.  We really need to think
more in terms of how this impacts a user and now how it's implemented
internally.  How does a user notice it's a reflink?  They don't as
implemented in btrfs and co.  Now on filesystem that don't always do
copy on write but might support reflinks (ocfs2, XFS in the future)
this becomes a bit more interesting - the difference he is that we
get an implicit fallocate when doing a real copy.  But if that's
something we have actual requests for that's how we should specify
it rather than in terms of arcane implementation details.