Messages in this thread | | | Date | Wed, 2 Mar 2022 13:59:52 -0800 | Subject | Re: [PATCH bpf-next v1 8/9] bpf: Introduce cgroup iter | From | Yonghong Song <> |
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On 2/25/22 3:43 PM, Hao Luo wrote: > Introduce a new type of iter prog: cgroup. Unlike other bpf_iter, this > iter doesn't iterate a set of kernel objects. Instead, it is supposed to > be parameterized by a cgroup id and prints only that cgroup. So one > needs to specify a target cgroup id when attaching this iter. > > The target cgroup's state can be read out via a link of this iter. > Typically, we can monitor cgroup creation and deletion using sleepable > tracing and use it to create corresponding directories in bpffs and pin > a cgroup id parameterized link in the directory. Then we can read the > auto-pinned iter link to get cgroup's state. The output of the iter link > is determined by the program. See the selftest test_cgroup_stats.c for > an example. > > Signed-off-by: Hao Luo <haoluo@google.com> > --- > include/linux/bpf.h | 1 + > include/uapi/linux/bpf.h | 6 ++ > kernel/bpf/Makefile | 2 +- > kernel/bpf/cgroup_iter.c | 141 +++++++++++++++++++++++++++++++++ > tools/include/uapi/linux/bpf.h | 6 ++ > 5 files changed, 155 insertions(+), 1 deletion(-) > create mode 100644 kernel/bpf/cgroup_iter.c > [...] > + > +static const struct seq_operations cgroup_iter_seq_ops = { > + .start = cgroup_iter_seq_start, > + .next = cgroup_iter_seq_next, > + .stop = cgroup_iter_seq_stop, > + .show = cgroup_iter_seq_show, > +}; > + > +BTF_ID_LIST_SINGLE(bpf_cgroup_btf_id, struct, cgroup) > + > +static int cgroup_iter_seq_init(void *priv_data, struct bpf_iter_aux_info *aux) > +{ > + *(u64 *)priv_data = aux->cgroup_id; > + return 0; > +} > + > +static void cgroup_iter_seq_fini(void *priv_data) > +{ > +} > + > +static const struct bpf_iter_seq_info cgroup_iter_seq_info = { > + .seq_ops = &cgroup_iter_seq_ops, > + .init_seq_private = cgroup_iter_seq_init, > + .fini_seq_private = cgroup_iter_seq_fini,
Since cgroup_iter_seq_fini() is a nop, you can just have .fini_seq_private = NULL,
> + .seq_priv_size = sizeof(u64), > +}; > + > +static int bpf_iter_attach_cgroup(struct bpf_prog *prog, > + union bpf_iter_link_info *linfo, > + struct bpf_iter_aux_info *aux) > +{ > + aux->cgroup_id = linfo->cgroup.cgroup_id; > + return 0; > +} > + > +static void bpf_iter_detach_cgroup(struct bpf_iter_aux_info *aux) > +{ > +} > + > +void bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info *aux, > + struct seq_file *seq) > +{ > + char buf[64] = {0};
Is this 64 the maximum possible cgroup path length? If there is a macro for that, I think it would be good to use it.
> + > + cgroup_path_from_kernfs_id(aux->cgroup_id, buf, sizeof(buf));
cgroup_path_from_kernfs_id() might fail in which case, buf will be 0. and cgroup_path will be nothing. I guess this might be the expected result. I might be good to add a comment to clarify in the code.
> + seq_printf(seq, "cgroup_id:\t%lu\n", aux->cgroup_id); > + seq_printf(seq, "cgroup_path:\t%s\n", buf); > +} > + > +int bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info *aux, > + struct bpf_link_info *info) > +{ > + info->iter.cgroup.cgroup_id = aux->cgroup_id; > + return 0; > +} > + > +DEFINE_BPF_ITER_FUNC(cgroup, struct bpf_iter_meta *meta, > + struct cgroup *cgroup) > + > +static struct bpf_iter_reg bpf_cgroup_reg_info = { > + .target = "cgroup", > + .attach_target = bpf_iter_attach_cgroup, > + .detach_target = bpf_iter_detach_cgroup,
The same ehre, since bpf_iter_detach_cgroup() is a nop, you can replace it with NULL in the above.
> + .show_fdinfo = bpf_iter_cgroup_show_fdinfo, > + .fill_link_info = bpf_iter_cgroup_fill_link_info, > + .ctx_arg_info_size = 1, > + .ctx_arg_info = { > + { offsetof(struct bpf_iter__cgroup, cgroup), > + PTR_TO_BTF_ID }, > + }, > + .seq_info = &cgroup_iter_seq_info, > +}; > + > +static int __init bpf_cgroup_iter_init(void) > +{ > + bpf_cgroup_reg_info.ctx_arg_info[0].btf_id = bpf_cgroup_btf_id[0]; > + return bpf_iter_reg_target(&bpf_cgroup_reg_info); > +} > + [...]
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