[PATCH] selftests/mm: fix read_file() return value check

[Hongfu Li <hongfu.li@linux.dev>]

From: Hongfu Li <lihongfu@kylinos.cn>

read_file() returns 0 on open/read failures and never returns negative
values. Existing < 0 error checks never trigger, so read failures are
silently ignored. Check for zero return to detect read_file() failures.

Also fix misleading error message in get_finfo(). The error string
incorrectly references read_num when reading uevent files.

Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
---
 tools/testing/selftests/mm/khugepaged.c | 4 ++--
 tools/testing/selftests/mm/vm_util.c    | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
index 10e8dedcb087..506310d4b4d5 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -138,8 +138,8 @@ static void get_finfo(const char *dir)
 		     major(path_stat.st_dev), minor(path_stat.st_dev))
 	    >= sizeof(path))
 		ksft_exit_fail_msg("%s: Pathname is too long\n", __func__);
-	if (read_file(path, buf, sizeof(buf)) < 0)
-		ksft_exit_fail_perror("read_file(read_num)");
+	if (!read_file(path, buf, sizeof(buf)))
+		ksft_exit_fail_perror("read_file(uevent)");
 	if (strstr(buf, "DEVTYPE=disk")) {
 		/* Found it */
 		if (snprintf(finfo.dev_queue_read_ahead_path,
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index ef1ea11981a7..2697d50d07f4 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -755,7 +755,7 @@ unsigned long read_num(const char *path)
 {
 	char buf[21];
 
-	if (read_file(path, buf, sizeof(buf)) < 0)
+	if (!read_file(path, buf, sizeof(buf)))
 		ksft_exit_fail_perror("read_file()");
 
 	return strtoul(buf, NULL, 10);
-- 
2.54.0