torture: Protect kvm-remote.sh directory trees from /tmp reaping

The kvm-remote.sh script places the datestamped directory containing
all the build artifacts in the destination systems' /tmp directories,
where they accumulate runtime artifacts such as console.log.  This works,
but some systems have a habit of removing files in /tmp that have not
been recently accessed.  This commit therefore runs a simple script that
periodically accesses all files in the datestamped directory.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm-remote-noreap.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Periodically scan a directory tree to prevent files from being reaped
+# by systemd and friends on long runs.
+#
+# Usage: kvm-remote-noreap.sh pathname
+#
+# Copyright (C) 2021 Facebook, Inc.
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+pathname="$1"
+if test "$pathname" = ""
+then
+	echo Usage: kvm-remote-noreap.sh pathname
+	exit 1
+fi
+if ! test -d "$pathname"
+then
+	echo  Usage: kvm-remote-noreap.sh pathname
+	echo "       pathname must be a directory."
+	exit 2
+fi
+
+while test -d "$pathname"
+do
+	find "$pathname" -type f -exec touch -c {} \; > /dev/null 2>&1
+	sleep 30
+done

tools/testing/selftests/rcutorture/bin/kvm-remote.sh

@@ -124,10 +124,11 @@ awk < "$rundir"/scenarios -v dest="$T/bin" -v rundir="$rundir" '
 	n = $1;
 	sub(/\./, "", n);
 	fn = dest "/kvm-remote-" n ".sh"
+	print "kvm-remote-noreap.sh " rundir " &" > fn;
 	scenarios = "";
 	for (i = 2; i <= NF; i++)
 		scenarios = scenarios " " $i;
-	print "kvm-test-1-run-batch.sh" scenarios > fn;
+	print "kvm-test-1-run-batch.sh" scenarios >> fn;
 	print "sync" >> fn;
 	print "rm " rundir "/remote.run" >> fn;
 }'