selftests/resctrl: Return -1 instead of errno on error

A number of functions in the resctrl selftests return errno. It is
problematic because errno is positive which is often counterintuitive.
Also, every site returning errno prints the error message already with
ksft_perror() so there is not much added value in returning the precise
error code.

Simply convert all places returning errno to return -1 that is typical
userspace error code in case of failures.

While at it, improve resctrl_val() comment to state that 0 means the
test was run (either pass or fail).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/resctrl/cache.c

@@ -126,7 +126,7 @@ static int get_llc_occu_resctrl(unsigned long *llc_occupancy)
 	if (!fp) {
 		ksft_perror("Failed to open results file");
 
-		return errno;
+		return -1;
 	}
 	if (fscanf(fp, "%lu", llc_occupancy) <= 0) {
 		ksft_perror("Could not get llc occupancy");
@@ -146,7 +146,7 @@ static int get_llc_occu_resctrl(unsigned long *llc_occupancy)
  * @llc_value:		perf miss value /
  *			llc occupancy value reported by resctrl FS
  *
- * Return:		0 on success. non-zero on failure.
+ * Return:		0 on success, < 0 on error.
  */
 static int print_results_cache(char *filename, int bm_pid,
 			       unsigned long llc_value)
@@ -161,7 +161,7 @@ static int print_results_cache(char *filename, int bm_pid,
 		if (!fp) {
 			ksft_perror("Cannot open results file");
 
-			return errno;
+			return -1;
 		}
 		fprintf(fp, "Pid: %d \t llc_value: %lu\n", bm_pid, llc_value);
 		fclose(fp);

tools/testing/selftests/resctrl/cat_test.c

@@ -53,7 +53,7 @@ static int check_results(struct resctrl_val_param *param, size_t span)
 	if (!fp) {
 		ksft_perror("Cannot open file");
 
-		return errno;
+		return -1;
 	}
 
 	while (fgets(temp, sizeof(temp), fp)) {
@@ -150,7 +150,7 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 
 	if (pipe(pipefd)) {
 		ksft_perror("Unable to create pipe");
-		return errno;
+		return -1;
 	}
 
 	fflush(stdout);

tools/testing/selftests/resctrl/cmt_test.c

@@ -39,7 +39,7 @@ static int check_results(struct resctrl_val_param *param, size_t span, int no_of
 	if (!fp) {
 		ksft_perror("Error in opening file");
 
-		return errno;
+		return -1;
 	}
 
 	while (fgets(temp, sizeof(temp), fp)) {

tools/testing/selftests/resctrl/mba_test.c

@@ -111,7 +111,7 @@ static int check_results(void)
 	if (!fp) {
 		ksft_perror(output);
 
-		return errno;
+		return -1;
 	}
 
 	runs = 0;

tools/testing/selftests/resctrl/mbm_test.c

@@ -61,7 +61,7 @@ static int check_results(size_t span)
 	if (!fp) {
 		ksft_perror(output);
 
-		return errno;
+		return -1;
 	}
 
 	runs = 0;

tools/testing/selftests/resctrl/resctrl_val.c

@@ -526,7 +526,7 @@ void signal_handler_unregister(void)
  * @bw_imc:		perf imc counter value
  * @bw_resc:		memory bandwidth value
  *
- * Return:		0 on success. non-zero on failure.
+ * Return:		0 on success, < 0 on error.
  */
 static int print_results_bw(char *filename,  int bm_pid, float bw_imc,
 			    unsigned long bw_resc)
@@ -542,14 +542,14 @@ static int print_results_bw(char *filename,  int bm_pid, float bw_imc,
 		if (!fp) {
 			ksft_perror("Cannot open results file");
 
-			return errno;
+			return -1;
 		}
 		if (fprintf(fp, "Pid: %d \t Mem_BW_iMC: %f \t Mem_BW_resc: %lu \t Difference: %lu\n",
 			    bm_pid, bw_imc, bw_resc, diff) <= 0) {
 			ksft_print_msg("Could not log results\n");
 			fclose(fp);
 
-			return errno;
+			return -1;
 		}
 		fclose(fp);
 	}
@@ -686,7 +686,7 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
  * @benchmark_cmd:	benchmark command and its arguments
  * @param:		parameters passed to resctrl_val()
  *
- * Return:		0 on success. non-zero on failure.
+ * Return:		0 when the test was run, < 0 on error.
  */
 int resctrl_val(const char * const *benchmark_cmd, struct resctrl_val_param *param)
 {
@@ -814,7 +814,7 @@ int resctrl_val(const char * const *benchmark_cmd, struct resctrl_val_param *par
 	/* Signal child to start benchmark */
 	if (sigqueue(bm_pid, SIGUSR1, value) == -1) {
 		ksft_perror("sigqueue SIGUSR1 to child");
-		ret = errno;
+		ret = -1;
 		goto out;
 	}
 

tools/testing/selftests/resctrl/resctrlfs.c

@@ -88,7 +88,7 @@ int umount_resctrlfs(void)
 	if (umount(mountpoint)) {
 		ksft_perror("Unable to umount resctrl");
 
-		return errno;
+		return -1;
 	}
 
 	return 0;