libceph: don't complain on msgpool alloc failures

The pool allocation failures are masked by the pool; there is no need to
spam the console about them.  (That's the whole point of having the pool
in the first place.)

Mark msg allocations whose failure is safely handled as such.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index d7adf15..bbd4a4b 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -238,7 +238,8 @@
 extern struct ceph_connection *ceph_con_get(struct ceph_connection *con);
 extern void ceph_con_put(struct ceph_connection *con);
 
-extern struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags);
+extern struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
+				     bool can_fail);
 extern void ceph_msg_kfree(struct ceph_msg *m);