NFS: Clean up NFSv4 XDR error message

Make it more useful for debugging purposes.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4xdr.c

@@ -2080,9 +2080,11 @@ out:
 
 #define READ_BUF(nbytes)  do { \
 	p = xdr_inline_decode(xdr, nbytes); \
-	if (!p) { \
-		printk(KERN_WARNING "%s: reply buffer overflowed in line %d.", \
-			       	__FUNCTION__, __LINE__); \
+	if (unlikely(!p)) { \
+		printk(KERN_INFO "%s: prematurely hit end of receive" \
+				" buffer\n", __FUNCTION__); \
+		printk(KERN_INFO "%s: xdr->p=%p, bytes=%u, xdr->end=%p\n", \
+				__FUNCTION__, xdr->p, nbytes, xdr->end); \
 		return -EIO; \
 	} \
 } while (0)