libceph: ceph_osd_{exists,is_up,is_down}(osd) definitions

Sync up with ceph.git definitions.  Bring in ceph_osd_is_down().
Signed-off-by: NIlya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: NAlex Elder <elder@linaro.org>

include/linux/ceph/osdmap.h

@@ -125,9 +125,21 @@ static inline void ceph_oid_copy(struct ceph_object_id *dest,
 	dest->name_len = src->name_len;
 }
 
+static inline int ceph_osd_exists(struct ceph_osdmap *map, int osd)
+{
+	return osd >= 0 && osd < map->max_osd &&
+	       (map->osd_state[osd] & CEPH_OSD_EXISTS);
+}
+
 static inline int ceph_osd_is_up(struct ceph_osdmap *map, int osd)
 {
-	return (osd < map->max_osd) && (map->osd_state[osd] & CEPH_OSD_UP);
+	return ceph_osd_exists(map, osd) &&
+	       (map->osd_state[osd] & CEPH_OSD_UP);
+}
+
+static inline int ceph_osd_is_down(struct ceph_osdmap *map, int osd)
+{
+	return !ceph_osd_is_up(map, osd);
 }
 
 static inline bool ceph_osdmap_flag(struct ceph_osdmap *map, int flag)