[dm-devel] [PATCH 4/5] dax: remove the copy_from_iter and copy_to_iter methods

[Christoph Hellwig]

On Sun, Dec 12, 2021 at 06:39:16AM -0800, Dan Williams wrote:
> >         /* flag to check if device supports synchronous flush */
> >         DAXDEV_SYNC,
> > +       /* do not use uncached operations to write data */
> > +       DAXDEV_CACHED,
> > +       /* do not use mcsafe operations to read data */
> > +       DAXDEV_NOMCSAFE,
> 
> Linus did not like the mcsafe name, and this brings it back. Let's
> flip the polarity to positively indicate which routine to use, and to
> match the 'nofault' style which says "copy and handle faults".
> 
> /* do not leave the caches dirty after writes */
> DAXDEV_NOCACHE
> 
> /* handle CPU fetch exceptions during reads */
> DAXDEV_NOMC
> 
> ...and then flip the use cases around.

Sure we can do that.  But let's finish the discussion if we actually
need the virtiofs special casing, as it seems pretty fishy in many
aspects.