Andrea Arcangeli [off-list ref] writes:

Hi Steve,

On Fri, Sep 26, 2014 at 03:03:48PM +0100, Steve Capper wrote:

quoted

This patch provides a general RCU implementation of get_user_pages_fast
that can be used by architectures that perform hardware broadcast of
TLB invalidations.

It is based heavily on the PowerPC implementation by Nick Piggin.

It'd be nice if you could also at the same time apply it to sparc and
powerpc in this same patchset to show the effectiveness of having a
generic version. Because if it's not a trivial drop-in replacement,
then this should go in arch/arm* instead of mm/gup.c...

on ppc64 we have one challenge, we do need to support hugepd. At the pmd
level we can have hugepte, normal pmd pointer or a pointer to hugepage
directory which is used in case of some sub-architectures/platforms. ie,
the below part of gup implementation in ppc64

else if (is_hugepd(pmdp)) {
	if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT,
			addr, next, write, pages, nr))
		return 0;


-aneesh