On 8/3/26 21:46, Chengkaitao wrote: > From: Kaitao Cheng <[email protected]> > > Add three kfuncs for BPF linked list queries: > - bpf_list_is_first(head, node): true if node is the first in the list. > - bpf_list_is_last(head, node): true if node is the last in the list. > - bpf_list_empty(head): true if the list has no entries. > > In previous versions, to implement the above functionality, it was ^ Currently, ..., it is
"The previous versions" would mislead readers, that you are referring to the previous versions of this series. Thanks, Leon > necessary to first call bpf_list_pop_front/back to retrieve the first > or last node before checking whether the passed-in node was the first > or last one. After the check, the node had to be pushed back into the > list using bpf_list_push_front/back, which was very inefficient.> > Now, with the bpf_list_is_first/last/empty kfuncs, we can directly > check whether a node is the first, last, or whether the list is empty, > without having to first retrieve the node. > > Signed-off-by: Kaitao Cheng <[email protected]> > --- > kernel/bpf/helpers.c | 38 ++++++++++++++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 15 +++++++++++++-- > 2 files changed, 51 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 407520fde668..476f5ad319e2 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2515,6 +2515,41 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(struct > bpf_list_head *head) > return (struct bpf_list_node *)h->prev; > } > > +__bpf_kfunc bool bpf_list_is_first(struct bpf_list_head *head, struct > bpf_list_node *node) > +{ > + struct list_head *h = (struct list_head *)head; > + struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node; > + > + if (READ_ONCE(kn->owner) != head) > + return false; > + > + return list_is_first(&kn->list_head, h); > +} > + > +__bpf_kfunc bool bpf_list_is_last(struct bpf_list_head *head, struct > bpf_list_node *node) > +{ > + struct list_head *h = (struct list_head *)head; > + struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node; > + > + if (READ_ONCE(kn->owner) != head) > + return false; > + > + return list_is_last(&kn->list_head, h); > +} > + > +__bpf_kfunc bool bpf_list_empty(struct bpf_list_head *head) > +{ > + struct list_head *h = (struct list_head *)head; > + > + /* If list_head was 0-initialized by map, bpf_obj_init_field wasn't > + * called on its fields, so init here > + */ > + if (unlikely(!h->next)) > + INIT_LIST_HEAD(h); > + > + return list_empty(h); > +} > + > __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, > struct bpf_rb_node *node) > { > @@ -4585,6 +4620,9 @@ BTF_ID_FLAGS(func, bpf_list_del, 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_list_add_impl) > +BTF_ID_FLAGS(func, bpf_list_is_first) > +BTF_ID_FLAGS(func, bpf_list_is_last) > +BTF_ID_FLAGS(func, bpf_list_empty) > 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) > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 5f55b68ed935..5e32e02429c4 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -12465,6 +12465,9 @@ enum special_kfunc_type { > KF_bpf_list_del, > KF_bpf_list_front, > KF_bpf_list_back, > + KF_bpf_list_is_first, > + KF_bpf_list_is_last, > + KF_bpf_list_empty, > KF_bpf_cast_to_kern_ctx, > KF_bpf_rdonly_cast, > KF_bpf_rcu_read_lock, > @@ -12527,6 +12530,9 @@ BTF_ID(func, bpf_list_pop_back) > BTF_ID(func, bpf_list_del) > BTF_ID(func, bpf_list_front) > BTF_ID(func, bpf_list_back) > +BTF_ID(func, bpf_list_is_first) > +BTF_ID(func, bpf_list_is_last) > +BTF_ID(func, bpf_list_empty) > BTF_ID(func, bpf_cast_to_kern_ctx) > BTF_ID(func, bpf_rdonly_cast) > BTF_ID(func, bpf_rcu_read_lock) > @@ -13003,7 +13009,10 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) > btf_id == special_kfunc_list[KF_bpf_list_pop_back] || > btf_id == special_kfunc_list[KF_bpf_list_del] || > btf_id == special_kfunc_list[KF_bpf_list_front] || > - btf_id == special_kfunc_list[KF_bpf_list_back]; > + btf_id == special_kfunc_list[KF_bpf_list_back] || > + btf_id == special_kfunc_list[KF_bpf_list_is_first] || > + btf_id == special_kfunc_list[KF_bpf_list_is_last] || > + btf_id == special_kfunc_list[KF_bpf_list_empty]; > } > > static bool is_bpf_rbtree_api_kfunc(u32 btf_id) > @@ -13126,7 +13135,9 @@ static bool check_kfunc_is_graph_node_api(struct > bpf_verifier_env *env, > ret = (kfunc_btf_id == > special_kfunc_list[KF_bpf_list_push_front_impl] || > kfunc_btf_id == > special_kfunc_list[KF_bpf_list_push_back_impl] || > kfunc_btf_id == special_kfunc_list[KF_bpf_list_add_impl] > || > - kfunc_btf_id == special_kfunc_list[KF_bpf_list_del]); > + kfunc_btf_id == special_kfunc_list[KF_bpf_list_del] || > + kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_first] > || > + kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last]); > break; > case BPF_RB_NODE: > ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] > ||
