highmem: mark k[un]map_atomic() with two arguments as deprecated

For backward compatibility, we still keep the deprecated form,
and will warn the users if they still use the deprecated one, like this:

drivers/block/drbd/drbd_bitmap.c: In function ‘bm_page_io_async’:
drivers/block/drbd/drbd_bitmap.c:973:3: warning: ‘kmap_atomic_deprecated’ is deprecated (declared at /home/wangcong/linux-2.6/include/linux/highmem.h:124)
drivers/block/drbd/drbd_bitmap.c:977:3: warning: ‘kunmap_atomic_deprecated’ is deprecated (declared at /home/wangcong/linux-2.6/include/linux/highmem.h:144)

Thanks to Nick Bowler for the cpp trick!

Cc: Cesar Eduardo Barros <cesarb@cesarb.net>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Cong Wang <amwang@redhat.com>

include/linux/highmem.h

@@ -109,20 +109,60 @@ static inline void kmap_atomic_idx_pop(void)
 #endif
 
 /*
- * Make both: kmap_atomic(page, idx) and kmap_atomic(page) work.
+ * NOTE:
+ * kmap_atomic() and kunmap_atomic() with two arguments are deprecated.
+ * We only keep them for backward compatibility, any usage of them
+ * are now warned.
  */
-#define kmap_atomic(page, args...) __kmap_atomic(page)
+
+#define PASTE(a, b) a ## b
+#define PASTE2(a, b) PASTE(a, b)
+
+#define NARG_(_2, _1, n, ...) n
+#define NARG(...) NARG_(__VA_ARGS__, 2, 1, :)
+
+static inline void *kmap_atomic(struct page *page)
+{
+	return __kmap_atomic(page);
+}
+
+static inline void __deprecated *kmap_atomic_deprecated(struct page *page,
+							enum km_type km)
+{
+	return __kmap_atomic(page);
+}
+
+#define kmap_atomic1(...) kmap_atomic(__VA_ARGS__)
+#define kmap_atomic2(...) kmap_atomic_deprecated(__VA_ARGS__)
+#define kmap_atomic(...) PASTE2(kmap_atomic, NARG(__VA_ARGS__)(__VA_ARGS__))
+
+static inline void __deprecated __kunmap_atomic_deprecated(void *addr,
+							enum km_type km)
+{
+	__kunmap_atomic(addr);
+}
 
 /*
  * Prevent people trying to call kunmap_atomic() as if it were kunmap()
  * kunmap_atomic() should get the return value of kmap_atomic, not the page.
  */
-#define kunmap_atomic(addr, args...)				\
-do {								\
-	BUILD_BUG_ON(__same_type((addr), struct page *));	\
-	__kunmap_atomic(addr);					\
+#define kunmap_atomic_deprecated(addr, km)                      \
+do {                                                            \
+	BUILD_BUG_ON(__same_type((addr), struct page *));       \
+	__kunmap_atomic_deprecated(addr, km);                   \
 } while (0)
 
+#define kunmap_atomic_withcheck(addr)                           \
+do {                                                            \
+	BUILD_BUG_ON(__same_type((addr), struct page *));       \
+	__kunmap_atomic(addr);                                  \
+} while (0)
+
+#define kunmap_atomic1(...) kunmap_atomic_withcheck(__VA_ARGS__)
+#define kunmap_atomic2(...) kunmap_atomic_deprecated(__VA_ARGS__)
+#define kunmap_atomic(...) PASTE2(kunmap_atomic, NARG(__VA_ARGS__)(__VA_ARGS__))
+/**** End of C pre-processor tricks for deprecated macros ****/
+
 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
 #ifndef clear_user_highpage
 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)