selftests: tracing: Fix to unmount tracefs for recovering environment

[ Upstream commit 7e021da ]

Fix to unmount the tracefs if the ftracetest mounted it for recovering
system environment. If the tracefs is already mounted, this does nothing.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/all/29fce076-746c-4650-8358-b4e0fa215cf7@sirena.org.uk/
Fixes: cbd965b ("ftrace/selftests: Return the skip code when tracing directory not configured in kernel")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/testing/selftests/ftrace/ftracetest

@@ -30,6 +30,9 @@ err_ret=1
 # kselftest skip code is 4
 err_skip=4
 
+# umount required
+UMOUNT_DIR=""
+
 # cgroup RT scheduling prevents chrt commands from succeeding, which
 # induces failures in test wakeup tests.  Disable for the duration of
 # the tests.
@@ -44,6 +47,9 @@ setup() {
 
 cleanup() {
   echo $sched_rt_runtime_orig > $sched_rt_runtime
+  if [ -n "${UMOUNT_DIR}" ]; then
+    umount ${UMOUNT_DIR} ||:
+  fi
 }
 
 errexit() { # message
@@ -155,11 +161,13 @@ if [ -z "$TRACING_DIR" ]; then
 	    mount -t tracefs nodev /sys/kernel/tracing ||
 	      errexit "Failed to mount /sys/kernel/tracing"
 	    TRACING_DIR="/sys/kernel/tracing"
+	    UMOUNT_DIR=${TRACING_DIR}
 	# If debugfs exists, then so does /sys/kernel/debug
 	elif [ -d "/sys/kernel/debug" ]; then
 	    mount -t debugfs nodev /sys/kernel/debug ||
 	      errexit "Failed to mount /sys/kernel/debug"
 	    TRACING_DIR="/sys/kernel/debug/tracing"
+	    UMOUNT_DIR=${TRACING_DIR}
 	else
 	    err_ret=$err_skip
 	    errexit "debugfs and tracefs are not configured in this kernel"