[PATCH] get_user_pages PageReserved fix

From David Miler.

get_user_pages() needs to avoid running page_cache_get() against
PageReserved pages.  Things like video driver and audio driver
remap_page_range() mappings.

mm/memory.c

@@ -571,7 +571,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 					i = -EFAULT;
 					goto out;
 				}
-				page_cache_get(pages[i]);
+				if (!PageReserved(pages[i]))
+					page_cache_get(pages[i]);
 			}
 			if (vmas)
 				vmas[i] = vma;