[PATCH] Fix oops in alloc_zeroed_user_highpage() when page is NULL

The generic and IA-64 versions of alloc_zeroed_user_highpage() don't
check the return value from alloc_page_vma().  This can lead to an oops
if we're OOM.

This fixes my oops on PPC64, but I haven't got an IA-64 machine/compiler
handy.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-ia64/page.h

@@ -79,6 +79,7 @@ do {						\
 #define alloc_zeroed_user_highpage(vma, vaddr) \
 ({						\
 	struct page *page = alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO, vma, vaddr); \
+	if (page)				\
  		flush_dcache_page(page);	\
 	page;					\
 })

include/linux/highmem.h

@@ -48,7 +48,9 @@ alloc_zeroed_user_highpage(struct vm_area_struct *vma, unsigned long vaddr)
 {
 	struct page *page = alloc_page_vma(GFP_HIGHUSER, vma, vaddr);
 
+	if (page)
 		clear_user_highpage(page, vaddr);
+
 	return page;
 }
 #endif