mds: treat open requests as non-idempotent

The problem is that the reply contains a capability, and as such
is statefull and can't be lost.  Forwards by the MDS on behalf of
the client, however, introduce the possibility of multiple copies
or a request in flight if one of the MDSs fails, and the client
will drop any duplicate replies it receives.

Alternatively, the client could _also_ parse duplicate responses
(i.e. call fill_trace).  I'm not sure if that's a good idea.  In
any case, MDS forwarded requests are only really important for
dealing with flash flood scenarios on extremely large clusters,
so let's just set this aside for now.

diff --git a/src/messages/MClientRequest.h b/src/messages/MClientRequest.h
index a5a2f9c79f774518ff77c5aa0046bcc691ae841a..6d76de6993eeb2b49cc855843423a616ef636dac 100644 (file)
--- a/src/messages/MClientRequest.h
+++ b/src/messages/MClientRequest.h
@@ -79,7 +79,7 @@ public:
   }
   bool is_idempotent() {
     if (head.op == CEPH_MDS_OP_OPEN) 
-      return open_file_mode_is_readonly();
+      return false;  //open_file_mode_is_readonly();
     return (head.op & CEPH_MDS_OP_WRITE) == 0;
   }
   bool auth_is_best() {