[Ocfs2-devel] [PATCH 07/25] vfs: combine the clone and dedupe into a single remap_file_range

[Christoph Hellwig]

On Mon, Oct 15, 2018 at 10:13:17AM -0700, Darrick J. Wong wrote:
> > RFR_TO_SRC_EOF is checked in generic_remap_file_range_prep,
> > so the file system should know about it  Also looking at it again now
> > it seems entirely superflous - we can just pass down then len == we
> > use in higher level code instead of having a flag and will side step
> > the issue here.
> 
> I'm not a fan of hidden behaviors like that, particularly when we
> already have a flags field where callers can explicitly ask for the
> to-eof behavior.

This just means we have a flag to mean ken is 0 and needs to be filled,
rather than encoding that in the field itself.  If you fell better we
can replace 0 with 0xffffffff and still encode it in the field.

> > RFR_CAN_SHORTEN is advisory as no one has to shorten, but that can
> > easily be solved by including it everywhere.
> 
> CAN_SHORTEN isn't included everywhere

Include it everywhere as in allow it in ever ->remap_file instance.

> I sort of thought about introducing a new copy_file_range flag that
> would just do deduplication and allow for opportunistic "dedup as much
> as you can" but ... meh.  Maybe I'll just drop the patch instead; we can
> revisit that when anyone wants a better dedupe interface.

Sounds fine to me.  The btrfs ioctl is really ugly, but then again
there is no pressing need for something better.