On Tue, 2024-02-27 at 14:55 -0800, Kui-Feng Lee wrote:
[...]
> > @@ -4509,6 +4514,28 @@ static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
> > return 0;
> > }
> >
> > +/* Sync autoload and autocreate state between struct_ops map and
> > + * referenced programs.
> > + */
> > +static void bpf_map__struct_ops_toggle_progs_autoload(struct bpf_map *map, bool autocreate)
> > +{
> > + struct bpf_program *prog;
> > + int i;
> > +
> > + for (i = 0; i < btf_vlen(map->st_ops->type); ++i) {
> > + prog = map->st_ops->progs[i];
> > +
> > + if (!prog || prog->autoload_user_set)
> > + continue;
> > +
> > + if (autocreate)
> > + prog->struct_ops_refs++;
> > + else
> > + prog->struct_ops_refs--;
> > + prog->autoload = prog->struct_ops_refs != 0;
> > + }
> > +}
> > +
>
> This part is related to the other patch [1], which allows
> a user to change the value of a function pointer field. The behavior of
> autocreate and autoload may suprise a user if the user call
> bpf_map__set_autocreate() after changing the value of a function pointer
> field.
>
> [1]
> https://lore.kernel.org/all/20240227010432.714127-1-thinker.li@xxxxxxxxx/
So, it appears that with shadow types users would have more or less
convenient way to disable / enable related BPF programs
(the references to programs are available, but reference counting
would have to be implemented by user using some additional data
structure, if needed).
I don't see a way to reconcile shadow types with this autoload/autocreate toggling
=> my last two patches would have to be dropped.
Wdyt?
