From: Kuan-Wei Chiu Date: Tue, 26 Aug 2025 06:23:14 +0000 (+0800) Subject: mm/slub: Fix cmp_loc_by_count() to return 0 when counts are equal X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e1c4350327b39c9cad27b6c5779b3754384f26c8;p=users%2Fhch%2Fmisc.git mm/slub: Fix cmp_loc_by_count() to return 0 when counts are equal The comparison function cmp_loc_by_count() used for sorting stack trace locations in debugfs currently returns -1 if a->count > b->count and 1 otherwise. This breaks the antisymmetry property required by sort(), because when two counts are equal, both cmp(a, b) and cmp(b, a) return 1. This can lead to undefined or incorrect ordering results. Fix it by updating the comparison logic to explicitly handle the case when counts are equal, and use cmp_int() to ensure the comparison function adheres to the required mathematical properties of antisymmetry. Fixes: 553c0369b3e1 ("mm/slub: sort debugfs output by frequency of stack traces") Reviewed-by: Joshua Hahn Signed-off-by: Kuan-Wei Chiu Reviewed-by: Harry Yoo Signed-off-by: Vlastimil Babka --- diff --git a/mm/slub.c b/mm/slub.c index d257141896c9..264fc76455d7 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7731,10 +7731,7 @@ static int cmp_loc_by_count(const void *a, const void *b, const void *data) struct location *loc1 = (struct location *)a; struct location *loc2 = (struct location *)b; - if (loc1->count > loc2->count) - return -1; - else - return 1; + return cmp_int(loc2->count, loc1->count); } static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)