sunrpc: turn swapper_enable/disable functions into rpc_xprt_ops

RDMA xprts don't have a sock_xprt, but an rdma_xprt, so the
xs_swapper_enable/disable functions will likely oops when fed an RDMA
xprt. Turn these functions into rpc_xprt_ops so that that doesn't
occur. For now the RDMA versions are no-ops that just return -EINVAL
on an attempt to swapon.

Cc: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/sunrpc/xprt.h

@@ -133,6 +133,8 @@ struct rpc_xprt_ops {
 	void		(*close)(struct rpc_xprt *xprt);
 	void		(*destroy)(struct rpc_xprt *xprt);
 	void		(*print_stats)(struct rpc_xprt *xprt, struct seq_file *seq);
+	int		(*enable_swap)(struct rpc_xprt *xprt);
+	void		(*disable_swap)(struct rpc_xprt *xprt);
 };
 
 /*
@@ -328,6 +330,18 @@ static inline __be32 *xprt_skip_transport_header(struct rpc_xprt *xprt, __be32 *
 	return p + xprt->tsh_size;
 }
 
+static inline int
+xprt_enable_swap(struct rpc_xprt *xprt)
+{
+	return xprt->ops->enable_swap(xprt);
+}
+
+static inline void
+xprt_disable_swap(struct rpc_xprt *xprt)
+{
+	xprt->ops->disable_swap(xprt);
+}
+
 /*
  * Transport switch helper functions
  */
@@ -346,8 +360,6 @@ void			xprt_release_rqst_cong(struct rpc_task *task);
 void			xprt_disconnect_done(struct rpc_xprt *xprt);
 void			xprt_force_disconnect(struct rpc_xprt *xprt);
 void			xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie);
-int			xs_swapper_enable(struct rpc_xprt *xprt);
-void			xs_swapper_disable(struct rpc_xprt *xprt);
 
 bool			xprt_lock_connect(struct rpc_xprt *, struct rpc_task *, void *);
 void			xprt_unlock_connect(struct rpc_xprt *, void *);

net/sunrpc/clnt.c

@@ -2495,7 +2495,7 @@ retry:
 			goto retry;
 		}
 
-		ret = xs_swapper_enable(xprt);
+		ret = xprt_enable_swap(xprt);
 		xprt_put(xprt);
 	}
 	return ret;
@@ -2522,7 +2522,7 @@ retry:
 			goto retry;
 		}
 
-		xs_swapper_disable(xprt);
+		xprt_disable_swap(xprt);
 		xprt_put(xprt);
 	}
 }

net/sunrpc/xprtrdma/transport.c

@@ -682,6 +682,17 @@ static void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
 	   r_xprt->rx_stats.bad_reply_count);
 }
 
+static int
+xprt_rdma_enable_swap(struct rpc_xprt *xprt)
+{
+	return -EINVAL;
+}
+
+static void
+xprt_rdma_disable_swap(struct rpc_xprt *xprt)
+{
+}
+
 /*
  * Plumbing for rpc transport switch and kernel module
  */
@@ -700,7 +711,9 @@ static struct rpc_xprt_ops xprt_rdma_procs = {
 	.send_request		= xprt_rdma_send_request,
 	.close			= xprt_rdma_close,
 	.destroy		= xprt_rdma_destroy,
-	.print_stats		= xprt_rdma_print_stats
+	.print_stats		= xprt_rdma_print_stats,
+	.enable_swap		= xprt_rdma_enable_swap,
+	.disable_swap		= xprt_rdma_disable_swap,
 };
 
 static struct xprt_class xprt_rdma = {

net/sunrpc/xprtsock.c

@@ -1980,14 +1980,14 @@ static void xs_set_memalloc(struct rpc_xprt *xprt)
 }
 
 /**
- * xs_swapper_enable - Tag this transport as being used for swap.
+ * xs_enable_swap - Tag this transport as being used for swap.
  * @xprt: transport to tag
  *
  * Take a reference to this transport on behalf of the rpc_clnt, and
  * optionally mark it for swapping if it wasn't already.
  */
-int
+static int
-xs_swapper_enable(struct rpc_xprt *xprt)
+xs_enable_swap(struct rpc_xprt *xprt)
 {
 	struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);
 
@@ -2002,14 +2002,14 @@ xs_swapper_enable(struct rpc_xprt *xprt)
 }
 
 /**
- * xs_swapper_disable - Untag this transport as being used for swap.
+ * xs_disable_swap - Untag this transport as being used for swap.
  * @xprt: transport to tag
  *
  * Drop a "swapper" reference to this xprt on behalf of the rpc_clnt. If the
  * swapper refcount goes to 0, untag the socket as a memalloc socket.
  */
-void
+static void
-xs_swapper_disable(struct rpc_xprt *xprt)
+xs_disable_swap(struct rpc_xprt *xprt)
 {
 	struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);
 
@@ -2025,6 +2025,17 @@ xs_swapper_disable(struct rpc_xprt *xprt)
 static void xs_set_memalloc(struct rpc_xprt *xprt)
 {
 }
+
+static int
+xs_enable_swap(struct rpc_xprt *xprt)
+{
+	return -EINVAL;
+}
+
+static void
+xs_disable_swap(struct rpc_xprt *xprt)
+{
+}
 #endif
 
 static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
@@ -2488,6 +2499,8 @@ static struct rpc_xprt_ops xs_local_ops = {
 	.close			= xs_close,
 	.destroy		= xs_destroy,
 	.print_stats		= xs_local_print_stats,
+	.enable_swap		= xs_enable_swap,
+	.disable_swap		= xs_disable_swap,
 };
 
 static struct rpc_xprt_ops xs_udp_ops = {
@@ -2507,6 +2520,8 @@ static struct rpc_xprt_ops xs_udp_ops = {
 	.close			= xs_close,
 	.destroy		= xs_destroy,
 	.print_stats		= xs_udp_print_stats,
+	.enable_swap		= xs_enable_swap,
+	.disable_swap		= xs_disable_swap,
 };
 
 static struct rpc_xprt_ops xs_tcp_ops = {
@@ -2523,6 +2538,8 @@ static struct rpc_xprt_ops xs_tcp_ops = {
 	.close			= xs_tcp_shutdown,
 	.destroy		= xs_destroy,
 	.print_stats		= xs_tcp_print_stats,
+	.enable_swap		= xs_enable_swap,
+	.disable_swap		= xs_disable_swap,
 };
 
 /*
@@ -2540,6 +2557,8 @@ static struct rpc_xprt_ops bc_tcp_ops = {
 	.close			= bc_close,
 	.destroy		= bc_destroy,
 	.print_stats		= xs_tcp_print_stats,
+	.enable_swap		= xs_enable_swap,
+	.disable_swap		= xs_disable_swap,
 };
 
 static int xs_init_anyaddr(const int family, struct sockaddr *sap)