NFSv4: Cap the transport reconnection timer at 1/2 lease period

We don't want to miss a lease period renewal due to the TCP connection
failing to reconnect in a timely fashion. To ensure this doesn't happen,
cap the reconnection timer so that we retry the connection attempt
at least every 1/2 lease period.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

3 files changed, 26 insertions, 0 deletions

diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index 062029ab344a..82e77198d17e 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -151,6 +151,9 @@ void nfs4_set_lease_period(struct nfs_client *clp,
         clp->cl_lease_time = lease;
         clp->cl_last_renewal = lastrenewed;
         spin_unlock(&clp->cl_lock);
+
+        /* Cap maximum reconnect timeout at 1/2 lease period */
+        rpc_cap_max_reconnect_timeout(clp->cl_rpcclient, lease >> 1);
 }
 
 /*
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index b6810c92b8bb..5c02b0691587 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -195,6 +195,8 @@ int		rpc_clnt_add_xprt(struct rpc_clnt *, struct xprt_create *,
                                 struct rpc_xprt *,
                                 void *),
                         void *data);
+void            rpc_cap_max_reconnect_timeout(struct rpc_clnt *clnt,
+                        unsigned long timeo);
 
 const char *rpc_proc_name(const struct rpc_task *task);
 #endif /* __KERNEL__ */
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index faac5472d14d..7f79fb7dc6a0 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -2676,6 +2676,27 @@ out_put_switch:
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_add_xprt);
 
+static int
+rpc_xprt_cap_max_reconnect_timeout(struct rpc_clnt *clnt,
+                struct rpc_xprt *xprt,
+                void *data)
+{
+        unsigned long timeout = *((unsigned long *)data);
+
+        if (timeout < xprt->max_reconnect_timeout)
+                xprt->max_reconnect_timeout = timeout;
+        return 0;
+}
+
+void
+rpc_cap_max_reconnect_timeout(struct rpc_clnt *clnt, unsigned long timeo)
+{
+        rpc_clnt_iterate_for_each_xprt(clnt,
+                        rpc_xprt_cap_max_reconnect_timeout,
+                        &timeo);
+}
+EXPORT_SYMBOL_GPL(rpc_cap_max_reconnect_timeout);
+
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 static void rpc_show_header(void)
 {