libceph: handle_one_map()

Separate osdmap handling from decoding and iterating over a bag of maps
in a fresh MOSDMap message.  This sets up the scene for the updated OSD
client.

Of particular importance here is the addition of pi->was_full, which
can be used to answer "did this pool go full -> not-full in this map?".
This is the key bit for supporting pool quotas.

We won't be able to downgrade map_sem for much longer, so drop
downgrade_write().

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/mon_client.c

@@ -376,6 +376,14 @@ void ceph_monc_got_map(struct ceph_mon_client *monc, int sub, u32 epoch)
 }
 EXPORT_SYMBOL(ceph_monc_got_map);
 
+void ceph_monc_renew_subs(struct ceph_mon_client *monc)
+{
+	mutex_lock(&monc->mutex);
+	__send_subscribe(monc);
+	mutex_unlock(&monc->mutex);
+}
+EXPORT_SYMBOL(ceph_monc_renew_subs);
+
 /*
  * Register interest in the next osdmap
  */