From: Kaitao Cheng <chengkaitao@kylinos.cn>

Add a node to both an rbtree and a list, retrieve the node from
the rbtree, use the obtained node pointer to remove it from the
list, and finally free the node.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
---
 .../testing/selftests/bpf/bpf_experimental.h  | 11 +++++
 .../selftests/bpf/progs/refcounted_kptr.c     | 41 +++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 2cd9165c7348..6d8175abc590 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -99,6 +99,17 @@ extern struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head) __ks
  */
 extern struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksym;
 
+/* Description
+ *	Remove 'node' from the BPF linked list with head 'head'.
+ *	The node must be in the list. Caller receives ownership of the
+ *	removed node and must release it with bpf_obj_drop.
+ * Returns
+ *	Pointer to the removed bpf_list_node, or NULL if 'node' is NULL
+ *	or not in the list.
+ */
+extern struct bpf_list_node *bpf_list_del(struct bpf_list_head *head,
+					  struct bpf_list_node *node) __ksym;
+
 /* Description
  *	Remove 'node' from rbtree with root 'root'
  * Returns
diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
index 1aca85d86aeb..2cb6dd73db7a 100644
--- a/tools/testing/selftests/bpf/progs/refcounted_kptr.c
+++ b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
@@ -367,6 +367,47 @@ long insert_rbtree_and_stash__del_tree_##rem_tree(void *ctx)		\
 INSERT_STASH_READ(true, "insert_stash_read: remove from tree");
 INSERT_STASH_READ(false, "insert_stash_read: don't remove from tree");
 
+/* Insert node_data into both rbtree and list, remove from tree, then remove
+ * from list via bpf_list_del using the node obtained from the tree.
+ */
+SEC("tc")
+__description("test_bpf_list_del: remove an arbitrary node from the list")
+__success __retval(0)
+long test_bpf_list_del(void *ctx)
+{
+	long err;
+	struct bpf_rb_node *rb;
+	struct bpf_list_node *l;
+	struct node_data *n;
+
+	err = __insert_in_tree_and_list(&head, &root, &lock);
+	if (err)
+		return err;
+
+	bpf_spin_lock(&lock);
+	rb = bpf_rbtree_first(&root);
+	if (!rb) {
+		bpf_spin_unlock(&lock);
+		return -4;
+	}
+
+	rb = bpf_rbtree_remove(&root, rb);
+	bpf_spin_unlock(&lock);
+	if (!rb)
+		return -5;
+	n = container_of(rb, struct node_data, r);
+
+	bpf_spin_lock(&lock);
+	l = bpf_list_del(&head, &n->l);
+	bpf_spin_unlock(&lock);
+	bpf_obj_drop(n);
+	if (!l)
+		return -6;
+
+	bpf_obj_drop(container_of(l, struct node_data, l));
+	return 0;
+}
+
 SEC("tc")
 __success
 long rbtree_refcounted_node_ref_escapes(void *ctx)
-- 
2.50.1 (Apple Git-155)