rhashtable: Add selftest for rhashtable_next_key()

Insert n elements, then verify:
  - NULL prev_key walks from the beginning, visiting all n
  - non-existing prev_key returns ERR_PTR(-ENOENT)

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/r/20260605-rhash-v7-2-5b8e05f8630d@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 0b33559a910b08448664e637ea8eb7588eff11cb..b767a38a74f97d3f23cf993218cbf8307c21bc91 100644 (file)
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -679,6 +679,78 @@ out:
        return err;
 }
 
+static int __init test_rhashtable_next_key(void)
+{
+       struct rhashtable_params params = test_rht_params;
+       struct test_obj_val key_missing = { .id = 99999, .tid = 0 };
+       struct test_obj_val *prev_key = NULL;
+       struct rhashtable ht;
+       struct test_obj *objs, *cur;
+       int i, count = 0, err;
+       int visited_keys[8] = { 0 };
+       const int n = ARRAY_SIZE(visited_keys);
+
+       params.nelem_hint = n;
+
+       err = rhashtable_init(&ht, &params);
+       if (err)
+               return err;
+
+       objs = kcalloc(n, sizeof(*objs), GFP_KERNEL);
+       if (!objs) {
+               rhashtable_destroy(&ht);
+               return -ENOMEM;
+       }
+
+       for (i = 0; i < n; i++) {
+               objs[i].value.id = i;
+               err = rhashtable_insert_fast(&ht, &objs[i].node, params);
+               if (err)
+                       goto out;
+       }
+
+       rcu_read_lock();
+
+       /* NULL prev_key: walk from the beginning, expect all n elements. */
+       while ((cur = rhashtable_next_key(&ht, prev_key))) {
+               if (IS_ERR(cur)) {
+                       err = -EINVAL;
+                       goto unlock;
+               }
+               count++;
+               prev_key = &cur->value;
+               visited_keys[cur->value.id] = 1;
+               if (count > n)
+                       break;
+       }
+
+       if (count != n) {
+               err = -EINVAL;
+               goto unlock;
+       }
+
+       for (i = 0; i < n; i++) {
+               if (!visited_keys[i]) {
+                       err = -EINVAL;
+                       goto unlock;
+               }
+       }
+
+       /* Non-existing prev_key: must return ERR_PTR(-ENOENT). */
+       cur = rhashtable_next_key(&ht, &key_missing);
+       if (!IS_ERR(cur) || PTR_ERR(cur) != -ENOENT)
+               err = -EINVAL;
+
+unlock:
+       rcu_read_unlock();
+out:
+       for (i = 0; i < n; i++)
+               rhashtable_remove_fast(&ht, &objs[i].node, params);
+       kfree(objs);
+       rhashtable_destroy(&ht);
+       return err;
+}
+
 static int __init test_rht_init(void)
 {
        unsigned int entries;
@@ -738,6 +810,9 @@ static int __init test_rht_init(void)
 
        test_insert_duplicates_run();
 
+       pr_info("Testing rhashtable_next_key: %s\n",
+               test_rhashtable_next_key() == 0 ? "pass" : "FAIL");
+
        if (!tcount)
                return 0;