v4.19.13 snapshot.
diff --git a/net/sunrpc/timer.c b/net/sunrpc/timer.c
new file mode 100644
index 0000000..08881d0
--- /dev/null
+++ b/net/sunrpc/timer.c
@@ -0,0 +1,122 @@
+/*
+ * linux/net/sunrpc/timer.c
+ *
+ * Estimate RPC request round trip time.
+ *
+ * Based on packet round-trip and variance estimator algorithms described
+ * in appendix A of "Congestion Avoidance and Control" by Van Jacobson
+ * and Michael J. Karels (ACM Computer Communication Review; Proceedings
+ * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988).
+ *
+ * This RTT estimator is used only for RPC over datagram protocols.
+ *
+ * Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>
+ */
+
+#include <asm/param.h>
+
+#include <linux/types.h>
+#include <linux/unistd.h>
+#include <linux/module.h>
+
+#include <linux/sunrpc/clnt.h>
+
+#define RPC_RTO_MAX (60*HZ)
+#define RPC_RTO_INIT (HZ/5)
+#define RPC_RTO_MIN (HZ/10)
+
+/**
+ * rpc_init_rtt - Initialize an RPC RTT estimator context
+ * @rt: context to initialize
+ * @timeo: initial timeout value, in jiffies
+ *
+ */
+void rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo)
+{
+ unsigned long init = 0;
+ unsigned int i;
+
+ rt->timeo = timeo;
+
+ if (timeo > RPC_RTO_INIT)
+ init = (timeo - RPC_RTO_INIT) << 3;
+ for (i = 0; i < 5; i++) {
+ rt->srtt[i] = init;
+ rt->sdrtt[i] = RPC_RTO_INIT;
+ rt->ntimeouts[i] = 0;
+ }
+}
+EXPORT_SYMBOL_GPL(rpc_init_rtt);
+
+/**
+ * rpc_update_rtt - Update an RPC RTT estimator context
+ * @rt: context to update
+ * @timer: timer array index (request type)
+ * @m: recent actual RTT, in jiffies
+ *
+ * NB: When computing the smoothed RTT and standard deviation,
+ * be careful not to produce negative intermediate results.
+ */
+void rpc_update_rtt(struct rpc_rtt *rt, unsigned int timer, long m)
+{
+ long *srtt, *sdrtt;
+
+ if (timer-- == 0)
+ return;
+
+ /* jiffies wrapped; ignore this one */
+ if (m < 0)
+ return;
+
+ if (m == 0)
+ m = 1L;
+
+ srtt = (long *)&rt->srtt[timer];
+ m -= *srtt >> 3;
+ *srtt += m;
+
+ if (m < 0)
+ m = -m;
+
+ sdrtt = (long *)&rt->sdrtt[timer];
+ m -= *sdrtt >> 2;
+ *sdrtt += m;
+
+ /* Set lower bound on the variance */
+ if (*sdrtt < RPC_RTO_MIN)
+ *sdrtt = RPC_RTO_MIN;
+}
+EXPORT_SYMBOL_GPL(rpc_update_rtt);
+
+/**
+ * rpc_calc_rto - Provide an estimated timeout value
+ * @rt: context to use for calculation
+ * @timer: timer array index (request type)
+ *
+ * Estimate RTO for an NFS RPC sent via an unreliable datagram. Use
+ * the mean and mean deviation of RTT for the appropriate type of RPC
+ * for frequently issued RPCs, and a fixed default for the others.
+ *
+ * The justification for doing "other" this way is that these RPCs
+ * happen so infrequently that timer estimation would probably be
+ * stale. Also, since many of these RPCs are non-idempotent, a
+ * conservative timeout is desired.
+ *
+ * getattr, lookup,
+ * read, write, commit - A+4D
+ * other - timeo
+ */
+unsigned long rpc_calc_rto(struct rpc_rtt *rt, unsigned int timer)
+{
+ unsigned long res;
+
+ if (timer-- == 0)
+ return rt->timeo;
+
+ res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer];
+ if (res > RPC_RTO_MAX)
+ res = RPC_RTO_MAX;
+
+ return res;
+}
+EXPORT_SYMBOL_GPL(rpc_calc_rto);