libceph: add ceph_pg_pool_by_id()

"Lookup pool info by ID" function is hidden in osdmap.c.  Expose it to
the rest of libceph.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

include/linux/ceph/osdmap.h

@@ -174,6 +174,9 @@ extern int ceph_calc_pg_acting(struct ceph_osdmap *osdmap,
 extern int ceph_calc_pg_primary(struct ceph_osdmap *osdmap,
 				struct ceph_pg pgid);
 
+extern struct ceph_pg_pool_info *ceph_pg_pool_by_id(struct ceph_osdmap *map,
+						    u64 id);
+
 extern const char *ceph_pg_pool_name_by_id(struct ceph_osdmap *map, u64 id);
 extern int ceph_pg_poolid_by_name(struct ceph_osdmap *map, const char *name);
 

net/ceph/osdmap.c

@@ -464,6 +464,11 @@ static struct ceph_pg_pool_info *__lookup_pg_pool(struct rb_root *root, u64 id)
 	return NULL;
 }
 
+struct ceph_pg_pool_info *ceph_pg_pool_by_id(struct ceph_osdmap *map, u64 id)
+{
+	return __lookup_pg_pool(&map->pg_pools, id);
+}
+
 const char *ceph_pg_pool_name_by_id(struct ceph_osdmap *map, u64 id)
 {
 	struct ceph_pg_pool_info *pi;