[PATCH v2 1/3] tools/mm/page_owner_sort: fix --sort option being silently ignored

[Ye Liu <ye.liu@linux.dev>]

From: Ye Liu <liuye@kylinos.cn>

When --sort is used without any short option (-a, -m, -p, etc.),
compare_flag remains COMP_NO_FLAG.  The switch (compare_flag) then
falls through to the COMP_NUM case and calls set_single_cmp(), which
unconditionally overwrites the sort conditions that parse_sort_args()
already configured.  This makes --sort silently ineffective unless a
short option is also supplied.

Split COMP_NO_FLAG out of the COMP_NUM fallthrough so that --sort is
respected when no short option is present.

Reproduction:
  # Before fix: ascending order (ignored --sort=-pid)
  ./page_owner_sort --sort=-pid input.txt output.txt
  # After fix: descending order as expected

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 tools/mm/page_owner_sort.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/mm/page_owner_sort.c b/tools/mm/page_owner_sort.c
index 35d3d254941c..3c86c8d0618c 100644
--- a/tools/mm/page_owner_sort.c
+++ b/tools/mm/page_owner_sort.c
@@ -821,6 +821,10 @@ int main(int argc, char **argv)
 		set_single_cmp(compare_stacktrace, SORT_ASC);
 		break;
 	case COMP_NO_FLAG:
+		if (sc.size > 0)
+			break;
+		set_single_cmp(compare_num, SORT_DESC);
+		break;
 	case COMP_NUM:
 		set_single_cmp(compare_num, SORT_DESC);
 		break;
-- 
2.25.1