Merge branch 'bpf-support-bpf-rbtree-traversal-and-list-peeking'

Martin KaFai Lau says:

====================
bpf: Support bpf rbtree traversal and list peeking

From: Martin KaFai Lau <martin.lau@kernel.org>

The RFC v1 [1] showed a fq qdisc implementation in bpf
that is much closer to the kernel sch_fq.c.

The fq example and bpf qdisc changes are separated out from this set.
This set is to focus on the kfunc and verifier changes that
enable the bpf rbtree traversal and list peeking.

v2:
- Added tests to check that the return value of
  the bpf_rbtree_{root,left,right} and bpf_list_{front,back} is
  marked as a non_own_ref node pointer. (Kumar)
- Added tests to ensure that the bpf_rbtree_{root,left,right} and
  bpf_list_{front,back} must be called after holding the spinlock.
- Squashed the selftests adjustment to the corresponding verifier
  changes to avoid bisect failure. (Kumar)
- Separated the bpf qdisc specific changes and fq selftest example
  from this set.

[1]: https://lore.kernel.org/bpf/20250418224652.105998-1-martin.lau@linux.dev/
====================

Link: https://patch.msgid.link/20250506015857.817950-1-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index e3a2662f4e33..78cefb41266a 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2293,6 +2293,26 @@ __bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
 	return __bpf_list_del(head, true);
 }
 
+__bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head)
+{
+	struct list_head *h = (struct list_head *)head;
+
+	if (list_empty(h) || unlikely(!h->next))
+		return NULL;
+
+	return (struct bpf_list_node *)h->next;
+}
+
+__bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head)
+{
+	struct list_head *h = (struct list_head *)head;
+
+	if (list_empty(h) || unlikely(!h->next))
+		return NULL;
+
+	return (struct bpf_list_node *)h->prev;
+}
+
 __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
 						  struct bpf_rb_node *node)
 {
@@ -2366,6 +2386,33 @@ __bpf_kfunc struct bpf_rb_node *bpf_rbtree_first(struct bpf_rb_root *root)
 	return (struct bpf_rb_node *)rb_first_cached(r);
 }
 
+__bpf_kfunc struct bpf_rb_node *bpf_rbtree_root(struct bpf_rb_root *root)
+{
+	struct rb_root_cached *r = (struct rb_root_cached *)root;
+
+	return (struct bpf_rb_node *)r->rb_root.rb_node;
+}
+
+__bpf_kfunc struct bpf_rb_node *bpf_rbtree_left(struct bpf_rb_root *root, struct bpf_rb_node *node)
+{
+	struct bpf_rb_node_kern *node_internal = (struct bpf_rb_node_kern *)node;
+
+	if (READ_ONCE(node_internal->owner) != root)
+		return NULL;
+
+	return (struct bpf_rb_node *)node_internal->rb_node.rb_left;
+}
+
+__bpf_kfunc struct bpf_rb_node *bpf_rbtree_right(struct bpf_rb_root *root, struct bpf_rb_node *node)
+{
+	struct bpf_rb_node_kern *node_internal = (struct bpf_rb_node_kern *)node;
+
+	if (READ_ONCE(node_internal->owner) != root)
+		return NULL;
+
+	return (struct bpf_rb_node *)node_internal->rb_node.rb_right;
+}
+
 /**
  * bpf_task_acquire - Acquire a reference to a task. A task acquired by this
  * kfunc which is not stored in a map as a kptr, must be released by calling
@@ -3209,11 +3256,16 @@ BTF_ID_FLAGS(func, bpf_list_push_front_impl)
 BTF_ID_FLAGS(func, bpf_list_push_back_impl)
 BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_rbtree_add_impl)
 BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_rbtree_root, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_rbtree_left, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_rbtree_right, KF_RET_NULL)
 
 #ifdef CONFIG_CGROUPS
 BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)