[openib-general] RFC: [PATCH untested] IB/uverbs: optimize registration for huge pages

[Roland Dreier]

    Michael> How does this look?  Is this the intended usage?

Looks OK, although I would like to see test results too.  However I
wonder what get_user_pages() does with a huge page region -- does it
give back huge pages or does it waste a lot of effort creating 4KB
pages to cover the region?

Also, this

 > +	u32 mask = 0;

and this

 > +	mem->page_size = ffs(mask) ? 1 << (ffs(mask) - 1) : (1 << 31);

makes me think that maybe we should change mem->page_size to an
unsigned long, since it's quite possible that a memory region spans
more than 2GB physically contiguous (especially if support for GB
pages on amd64 is added).

 - R.