bpf: add new BPF_CGROUP_ITER_CHILDREN control option

Currently, the BPF cgroup iterator supports walking descendants in
either pre-order (BPF_CGROUP_ITER_DESCENDANTS_PRE) or post-order
(BPF_CGROUP_ITER_DESCENDANTS_POST). These modes perform an exhaustive
depth-first search (DFS) of the hierarchy. In scenarios where a BPF
program may need to inspect only the direct children of a given parent
cgroup, a full DFS is unnecessarily expensive.

This patch introduces a new BPF cgroup iterator control option,
BPF_CGROUP_ITER_CHILDREN. This control option restricts the traversal
to the immediate children of a specified parent cgroup, allowing for
more targeted and efficient iteration, particularly when exhaustive
depth-first search (DFS) traversal is not required.

Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Link: https://lore.kernel.org/r/20260127085112.3608687-1-mattbobrowski@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Matt Bobrowski
2026-01-27 08:51:10 +00:00
committed by Andrii Nakryiko
parent 5ee8863eaf
commit ed6bb65cf1

View File

@@ -119,6 +119,14 @@ enum bpf_cgroup_iter_order {
BPF_CGROUP_ITER_DESCENDANTS_PRE, /* walk descendants in pre-order. */
BPF_CGROUP_ITER_DESCENDANTS_POST, /* walk descendants in post-order. */
BPF_CGROUP_ITER_ANCESTORS_UP, /* walk ancestors upward. */
/*
* Walks the immediate children of the specified parent
* cgroup_subsys_state. Unlike BPF_CGROUP_ITER_DESCENDANTS_PRE,
* BPF_CGROUP_ITER_DESCENDANTS_POST, and BPF_CGROUP_ITER_ANCESTORS_UP
* the iterator does not include the specified parent as one of the
* returned iterator elements.
*/
BPF_CGROUP_ITER_CHILDREN,
};
union bpf_iter_link_info {