nfsd: provide callbacks on svc_xprt deletion

NFSv4.1 needs warning when a client tcp connection goes down, if that
connection is being used as a backchannel, so that it can warn the
client that it has lost the backchannel connection.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index bb18297..bbdb680 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -33,6 +33,16 @@ struct svc_xprt_class {
 	u32			xcl_max_payload;
 };
 
+/*
+ * This is embedded in an object that wants a callback before deleting
+ * an xprt; intended for use by NFSv4.1, which needs to know when a
+ * client's tcp connection (and hence possibly a backchannel) goes away.
+ */
+struct svc_xpt_user {
+	struct list_head list;
+	void (*callback)(struct svc_xpt_user *);
+};
+
 struct svc_xprt {
 	struct svc_xprt_class	*xpt_class;
 	struct svc_xprt_ops	*xpt_ops;
@@ -67,10 +77,25 @@ struct svc_xprt {
 	struct sockaddr_storage	xpt_remote;	/* remote peer's address */
 	size_t			xpt_remotelen;	/* length of address */
 	struct rpc_wait_queue	xpt_bc_pending;	/* backchannel wait queue */
+	struct list_head	xpt_users;	/* callbacks on free */
 
 	struct net		*xpt_net;
 };
 
+static inline void register_xpt_user(struct svc_xprt *xpt, struct svc_xpt_user *u)
+{
+	spin_lock(&xpt->xpt_lock);
+	list_add(&u->list, &xpt->xpt_users);
+	spin_unlock(&xpt->xpt_lock);
+}
+
+static inline void unregister_xpt_user(struct svc_xprt *xpt, struct svc_xpt_user *u)
+{
+	spin_lock(&xpt->xpt_lock);
+	list_del_init(&u->list);
+	spin_unlock(&xpt->xpt_lock);
+}
+
 int	svc_reg_xprt_class(struct svc_xprt_class *);
 void	svc_unreg_xprt_class(struct svc_xprt_class *);
 void	svc_xprt_init(struct svc_xprt_class *, struct svc_xprt *,