smb3: remind users that witness protocol is experimental

warn_once when using the witness protocol that it is experimental
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Samuel Cabrero <scabrero@suse.de>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>

fs/cifs/fs_context.c

@@ -1098,6 +1098,7 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 			goto cifs_parse_mount_err;
 #endif
 		ctx->witness = true;
+		pr_warn_once("Witness protocol support is experimental\n");
 		break;
 	case Opt_rootfs:
 #ifdef CONFIG_CIFS_ROOT