xprtrdma: Increase default credit limit

In preparation for similar increases on NFS/RDMA servers, bump the
advertised credit limit for RPC/RDMA to 128. This allocates some
extra resources, but the client will continue to allow only the
number of RPCs in flight that the server requests via its advertised
credit limit.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-By: Sagi Grimberg <sagig@mellanox.com>
Tested-by: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/xprtrdma.h

@@ -49,7 +49,7 @@
  * a single chunk type per message is supported currently.
  */
 #define RPCRDMA_MIN_SLOT_TABLE	(2U)
-#define RPCRDMA_DEF_SLOT_TABLE	(32U)
+#define RPCRDMA_DEF_SLOT_TABLE	(128U)
 #define RPCRDMA_MAX_SLOT_TABLE	(256U)
 
 #define RPCRDMA_DEF_INLINE  (1024)	/* default inline max */