Re: [PATCH bpf-next v8 0/8] bpf: Extend the bpf_list family of APIs

Emil Tsalapatis
2026-03-19T16:19:01Z

On Mon Mar 16, 2026 at 7:28 AM EDT, Chengkaitao wrote:
> From: Kaitao Cheng <chengkaitao@kylinos.cn>
>
> In BPF, a list can only be used to implement a stack structure.
> Due to an incomplete API set, only FIFO or LIFO operations are
> supported. The patches enhance the BPF list API, making it more
> list-like.
>
> Five new kfuncs have been added:
> bpf_list_del: remove a node from the list
> bpf_list_add_impl: insert a node after a given list node
> bpf_list_is_first: check if a node is the first in the list
> bpf_list_is_last: check if a node is the last in the list
> bpf_list_empty: check if the list is empty
>
> refactor kfunc checks to table-driven approach, and add test cases for
> the aforementioned kfuncs.
>

By the way,
https://sashiko.dev/#/message/20260316112843.78657-1-pilgrimtao%40gmail.com
has some additional feedback apart from those of the list bot.

> Changes in v8:
> - Use [patch v7 5/5] as the start of the patch series
> - Introduce double pointer prev_ptr in __bpf_list_del
> - Extract refactored __bpf_list_del/add into separate patches
> - Allow bpf_list_front/back result as the prev argument of bpf_list_add
> - Split test cases
>
> Changes in v7:
> - Replace bpf_list_node_is_edge with bpf_list_is_first/is_last
> - Reimplement __bpf_list_del and __bpf_list_add
> - Simplify test cases
>
> Changes in v6:
> - Merge [patch v5 (2,4,6)/6] into [patch v6 4/5]
> - If list_head was 0-initialized, init it
> - refactor kfunc checks to table-driven approach
>
> Changes in v5:
> - Fix bpf_obj leak on bpf_list_add_impl error
>
> Changes in v4:
> - [patch v3 1/6] Revert to version v1
> - Change the parameters of bpf_list_add_impl to (head, new, prev, ...)
>
> Changes in v3:
> - Add a new lock_rec member to struct bpf_reference_state for lock
> holding detection.
> - Add test cases to verify that the verifier correctly restricts calls
> to bpf_list_del when the spin_lock is not held.
>
> Changes in v2:
> - Remove the head parameter from bpf_list_del
> - Add bpf_list_add/is_first/is_last/empty to API and test cases
>
> Link to v7:
> https://lore.kernel.org/all/20260308134614.29711-1-pilgrimtao@gmail.com/
>
> Link to v6:
> https://lore.kernel.org/all/20260304143459.78059-1-pilgrimtao@gmail.com/
>
> Link to v5:
> https://lore.kernel.org/all/20260304031606.43884-1-pilgrimtao@gmail.com/
>
> Link to v4:
> https://lore.kernel.org/all/20260303135219.33726-1-pilgrimtao@gmail.com/
>
> Link to v3:
> https://lore.kernel.org/all/20260302124028.82420-1-pilgrimtao@gmail.com/
>
> Link to v2:
> https://lore.kernel.org/all/20260225092651.94689-1-pilgrimtao@gmail.com/
>
> Link to v1:
> https://lore.kernel.org/all/20260209025250.55750-1-pilgrimtao@gmail.com/
>
> Kaitao Cheng (8):
> bpf: refactor kfunc checks using table-driven approach in verifier
> bpf: refactor __bpf_list_del to take list node pointer
> bpf: Introduce the bpf_list_del kfunc.
> bpf: refactor __bpf_list_add to take insertion point via **prev_ptr
> bpf: Add bpf_list_add_impl to insert node after a given list node
> bpf: allow bpf_list_front/back result as the prev argument of
> bpf_list_add_impl
> bpf: add bpf_list_is_first/last/empty kfuncs
> selftests/bpf: Add test cases for
> bpf_list_del/add/is_first/is_last/empty
>
> kernel/bpf/helpers.c | 121 +++++--
> kernel/bpf/verifier.c | 116 +++++--
> .../testing/selftests/bpf/bpf_experimental.h | 16 +
> .../selftests/bpf/progs/refcounted_kptr.c | 311 ++++++++++++++++++
> 4 files changed, 519 insertions(+), 45 deletions(-)