RadosClient: Avoid the DispatchQueue for OSD responses.

Prior to this change, reader thread puts the response on the DispatchQueue
and Dispatcher thread would call librados callbacks (C_aio_Ack, C_Safe_Cond).
The single DispatchQueue and Dispatcher thread (per client) would become
a bottleneck with multiple OSDs in the cluster.
Similar to fast-dispatch changes on the OSD, DispatchQueue/thread are removed
and librados internal callbacks will be called from reader thread context.

Signed-off-by: Sushma Gurram <sushma.gurram@sandisk.com>
Signed-off-by: Somnath Roy <somnath.roy@sandisk.com>

Reviewed-by: Greg Farnum <greg@inktank.com>

src/librados/RadosClient.h

@@ -141,6 +141,18 @@ public:
   void get();
   bool put();
   void blacklist_self(bool set);
+
+private:
+  bool ms_can_fast_dispatch_any() const { return true; }
+  bool ms_can_fast_dispatch(Message *m) const {
+    switch (m->get_type()) {
+    case CEPH_MSG_OSD_OPREPLY:
+      return true;
+    default:
+      return false;
+    }
+  }
+  void ms_fast_dispatch(Message *m) { ms_dispatch(m); }
 };
 
 #endif