ceph: resubmit requests on pg mapping change (not just primary change)

OSD requests need to be resubmitted on any pg mapping change, not just when
the pg primary changes.  Resending only when the primary changes results in
occasional 'hung' requests during osd cluster recovery or rebalancing.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/rados.h b/fs/ceph/rados.h
index a1fc1d0..fd56451 100644
--- a/fs/ceph/rados.h
+++ b/fs/ceph/rados.h
@@ -58,6 +58,7 @@
 #define CEPH_PG_LAYOUT_LINEAR 2
 #define CEPH_PG_LAYOUT_HYBRID 3
 
+#define CEPH_PG_MAX_SIZE      16  /* max # osds in a single pg */
 
 /*
  * placement group.