On Wed, Aug 27, 2014 at 01:50:28PM +0100, Steve Capper wrote:

On Wed, Aug 27, 2014 at 09:54:42AM +0100, Will Deacon wrote:

quoted

On Thu, Aug 21, 2014 at 04:43:27PM +0100, Steve Capper wrote:

quoted

@@ -672,3 +676,277 @@ struct page *get_dump_page(unsigned long addr)
 	return page;
 }
 #endif /* CONFIG_ELF_CORE */
+
+#ifdef CONFIG_HAVE_RCU_GUP
+
+#ifdef __HAVE_ARCH_PTE_SPECIAL

Do we actually require this (pte special) if hugepages are disabled or
not supported?

We need this logic if we want use fast_gup on normal pages safely. The special
bit indicates that we should not attempt to take a reference to the underlying
page.

Huge pages are guaranteed not to be special.

Gah, I somehow mixed up sp-litting and sp-ecial. Step away from the
computer.

In which case, the patch looks fine. You might need to repost with '[PATCH]'
instead of '[PATH]', in case you confused people's filters.

Will