[PATCH] pfnmap: do_no_page BUG_ON again

Use copy_user_highpage directly instead of cow_user_page in do_no_page:
in the immediately following page_cache_release, and elsewhere, it is
assuming that new_page is normal. If any VM_PFNMAP driver can get to
do_no_page, it's just a BUG (but not in the case of do_anonymous_page).

Signed-off-by: Hugh Dickins <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/memory.c

···
 	int anon = 0;
 
 	pte_unmap(page_table);
+	BUG_ON(vma->vm_flags & VM_PFNMAP);
+
 	if (vma->vm_file) {
 		mapping = vma->vm_file->f_mapping;
 		sequence = mapping->truncate_count;
···
 		page = alloc_page_vma(GFP_HIGHUSER, vma, address);
 		if (!page)
 			goto oom;
-		cow_user_page(page, new_page, address);
+		copy_user_highpage(page, new_page, address);
 		page_cache_release(new_page);
 		new_page = page;
 		anon = 1;