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bpf: Introduce css open-coded iterator kfuncs

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This Patch adds kfuncs bpf_iter_css_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css in open-coded iterator
style. These kfuncs actually wrapps css_next_descendant_{pre, post}.
css_iter can be used to:

1) iterating a sepcific cgroup tree with pre/post/up order

2) iterating cgroup_subsystem in BPF Prog, like
for_each_mem_cgroup_tree/cpuset_for_each_descendant_pre in kernel.

The API design is consistent with cgroup_iter. bpf_iter_css_new accepts
parameters defining iteration order and starting css. Here we also reuse
BPF_CGROUP_ITER_DESCENDANTS_PRE, BPF_CGROUP_ITER_DESCENDANTS_POST,
BPF_CGROUP_ITER_ANCESTORS_UP enums.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-5-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Chuyi Zhou 2023-10-18 14:17:42 +08:00 committed by Alexei Starovoitov
parent c68a78ffe2
commit 7251d0905e
3 changed files with 74 additions and 0 deletions
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65
kernel/bpf/cgroup_iter.c
View File

@ -294,3 +294,68 @@ static int __init bpf_cgroup_iter_init(void)
}
late_initcall(bpf_cgroup_iter_init);
struct bpf_iter_css {
__u64 __opaque[3];
} __attribute__((aligned(8)));
struct bpf_iter_css_kern {
struct cgroup_subsys_state *start;
struct cgroup_subsys_state *pos;
unsigned int flags;
} __attribute__((aligned(8)));
__diag_push();
__diag_ignore_all("-Wmissing-prototypes",
"Global functions as their definitions will be in vmlinux BTF");
__bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it,
struct cgroup_subsys_state *start, unsigned int flags)
{
struct bpf_iter_css_kern *kit = (void *)it;
BUILD_BUG_ON(sizeof(struct bpf_iter_css_kern) > sizeof(struct bpf_iter_css));
BUILD_BUG_ON(__alignof__(struct bpf_iter_css_kern) != __alignof__(struct bpf_iter_css));
kit->start = NULL;
switch (flags) {
case BPF_CGROUP_ITER_DESCENDANTS_PRE:
case BPF_CGROUP_ITER_DESCENDANTS_POST:
case BPF_CGROUP_ITER_ANCESTORS_UP:
break;
default:
return -EINVAL;
}
kit->start = start;
kit->pos = NULL;
kit->flags = flags;
return 0;
}
__bpf_kfunc struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it)
{
struct bpf_iter_css_kern *kit = (void *)it;
if (!kit->start)
return NULL;
switch (kit->flags) {
case BPF_CGROUP_ITER_DESCENDANTS_PRE:
kit->pos = css_next_descendant_pre(kit->pos, kit->start);
break;
case BPF_CGROUP_ITER_DESCENDANTS_POST:
kit->pos = css_next_descendant_post(kit->pos, kit->start);
break;
case BPF_CGROUP_ITER_ANCESTORS_UP:
kit->pos = kit->pos ? kit->pos->parent : kit->start;
}
return kit->pos;
}
__bpf_kfunc void bpf_iter_css_destroy(struct bpf_iter_css *it)
{
}
__diag_pop();

3
kernel/bpf/helpers.c
View File

@ -2566,6 +2566,9 @@ BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_iter_task_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_css_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_iter_css_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_css_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)

6
tools/testing/selftests/bpf/bpf_experimental.h
View File

@ -471,4 +471,10 @@ extern int bpf_iter_task_new(struct bpf_iter_task *it,
extern struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it) __weak __ksym;
extern void bpf_iter_task_destroy(struct bpf_iter_task *it) __weak __ksym;
struct bpf_iter_css;
extern int bpf_iter_css_new(struct bpf_iter_css *it,
struct cgroup_subsys_state *start, unsigned int flags) __weak __ksym;
extern struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) __weak __ksym;
extern void bpf_iter_css_destroy(struct bpf_iter_css *it) __weak __ksym;
#endif