Re: [PATCH bpf-next 03/29] bpf: introduce BPF token object

Matthew Wilcox
2024-01-05T20:32:53Z

On Fri, Jan 05, 2024 at 12:25:42PM -0800, Linus Torvalds wrote:
> > diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
> > +
> > +static void bpf_token_free(struct bpf_token *token)
> > +{
> > + put_user_ns(token->userns);
> > + kvfree(token);
> > +}
>
> > +int bpf_token_create(union bpf_attr *attr)
> > +{
> > ....
> > + token = kvzalloc(sizeof(*token), GFP_USER);
>
> Ok, so the kvzalloc() and kvfree() certainly line up, but why use them at all?
>
> kvmalloc() and friends are for "use kmalloc, and fall back on vmalloc
> for big allocations when that fails".
>
> For just a structure, a plain 'kzalloc()/kfree()' pair would seem to
> make much more sense.

I can't tell from the description whether there are going to be a lot of
these. If there are, it might make sense to create a slab cache for
them rather than get them from the general-purpose kmalloc caches.