swap_info: SWAP_HAS_CACHE cleanups

Though swap_count() is useful, I'm finding that swap_has_cache() and
encode_swapmap() obscure what happens in the swap_map entry, just at
those points where I need to understand it.  Remove them, and pass
more usable "usage" values to scan_swap_map(), swap_entry_free() and
__swap_duplicate(), instead of the SWAP_MAP and SWAP_CACHE enum.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 109dfe7..c9d8870 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -154,7 +154,7 @@
 #define SWAP_MAP_MAX	0x7ffe
 #define SWAP_MAP_BAD	0x7fff
 #define SWAP_HAS_CACHE  0x8000		/* There is a swap cache of entry. */
-#define SWAP_COUNT_MASK (~SWAP_HAS_CACHE)
+
 /*
  * The in-memory structure used to track swap areas.
  */