include/linux/mm.h: add PAGE_ALIGNED() helper

To test whether an address is aligned to PAGE_SIZE.

Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -52,6 +52,9 @@ extern unsigned long sysctl_admin_reserve_kbytes;
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
 
+/* test whether an address (unsigned long or pointer) is aligned to PAGE_SIZE */
+#define PAGE_ALIGNED(addr)	IS_ALIGNED((unsigned long)addr, PAGE_SIZE)
+
 /*
  * Linux kernel virtual memory manager primitives.
  * The idea being to have a "virtual" mm in the same way