selftests/cgroup: use runtime page size for zswpin check

test_zswapin compares memory.stat:zswpin (counted in pages) against a byte
threshold converted with PAGE_SIZE.  In cgroup selftests, PAGE_SIZE is
hardcoded to 4096, which makes the conversion wrong on systems with non-4K
base pages (e.g.  64K).

As a result, the test requires too many pages to pass and fails spuriously
even when zswap is working.

Use sysconf(_SC_PAGESIZE) for the zswpin threshold conversion so the check
matches the actual system page size.

Link: https://lore.kernel.org/20260424040059.12940-4-li.wang@linux.dev
Signed-off-by: Li Wang <li.wang@linux.dev>
Reviewed-by: Yosry Ahmed <yosry@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
index 47709cbdcdf1c838e6e74c5efe006b3e41772b0d..37aa83c2f1bfe31f96ff4a0adedad06826f431d7 100644 (file)
--- a/tools/testing/selftests/cgroup/test_zswap.c
+++ b/tools/testing/selftests/cgroup/test_zswap.c
@@ -245,7 +245,7 @@ static int test_zswapin(const char *root)
                goto out;
        }
 
-       if (zswpin < MB(24) / PAGE_SIZE) {
+       if (zswpin < MB(24) / sysconf(_SC_PAGESIZE)) {
                ksft_print_msg("at least 24MB should be brought back from zswap\n");
                goto out;
        }