More carefully enable tracing in run-tests

run-tests.sh has a -t argument which takes a whitespace seperated string
of globs of events to enable.  This was hard to use and made it very
easy to accidentally expand the globs at the wrong place in the script.

This makes each -t argument specify a single word glob which is stored
in an array so the glob isn't expanded until it's applied to the trace
event path.   We also add an error for -t globs that didn't match any
events and add a message with the count of -t arguments and enabled
events.

Signed-off-by: Zach Brown <zab@versity.com>

tests/run-tests.sh

@@ -62,6 +62,7 @@ $(basename $0) options:
               | exist.  Previous results will be deleted as each test runs.
     -s        | Skip git repo checkouts.
     -t        | Enabled trace events that match the given glob argument.
+              | Multiple options enable multiple globbed events.
     -X        | xfstests git repo. Used by tests/xfstests.sh.
     -x        | xfstests git branch to checkout and track.
     -y        | xfstests ./check additional args
@@ -77,6 +78,9 @@ done
 T_TRACE_DUMP="0"
 T_TRACE_PRINTK="0"
 
+# array declarations to be able to use array ops
+declare -a T_TRACE_GLOB
+
 while true; do
 	case $1 in
 	-a)
@@ -147,7 +151,7 @@ while true; do
 		;;
 	-t)
 		test -n "$2" || die "-t must have trace glob argument"
-		T_TRACE_GLOB="$2"
+		T_TRACE_GLOB+=("$2")
 		shift
 		;;
 	-X)
@@ -314,12 +318,17 @@ if [ -n "$T_INSMOD" ]; then
 	cmd insmod "$T_KMOD/src/scoutfs.ko"
 fi
 
-if [ -n "$T_TRACE_GLOB" ]; then
-	msg "enabling trace events"
+nr_globs=${#T_TRACE_GLOB[@]}
+if [ $nr_globs -gt 0 ]; then
 	echo 0 > /sys/kernel/debug/tracing/events/scoutfs/enable
-	for g in $T_TRACE_GLOB; do
+
+	for g in "${T_TRACE_GLOB[@]}"; do
 		for e in /sys/kernel/debug/tracing/events/scoutfs/$g/enable; do
-			echo 1 > $e
+			if test -w "$e"; then
+				echo 1 > "$e"
+			else
+				die "-t glob '$g' matched no scoutfs events"
+			fi
 		done
 	done
 
@@ -329,6 +338,9 @@ if [ -n "$T_TRACE_GLOB" ]; then
 	cmd cat /sys/kernel/debug/tracing/set_event
 	cmd grep .  /sys/kernel/debug/tracing/options/trace_printk \
 		    /proc/sys/kernel/ftrace_dump_on_oops
+
+	nr_events=$(cat /sys/kernel/debug/tracing/set_event | wc -l)
+	msg "enabled $nr_events trace events from $nr_globs -t globs"
 fi
 
 #