Re: [PATCH] libbpf: Fix is_pow_of_2

[Tiezhu Yang]

On 06/22/2022 07:03 AM, Zvi Effron wrote:
> On Sun, Jun 19, 2022 at 12:13 PM Pavel Machek <pavel@xxxxxx> wrote:
> > Hi!
> >
> > > From: Yuze Chi <chiyuze@xxxxxxxxxx>
> > >
> > > +++ b/tools/lib/bpf/libbpf.c
> > > @@ -4956,7 +4956,7 @@ static void bpf_map__destroy(struct bpf_map *map);
> > >
> > > static bool is_pow_of_2(size_t x)
> > > {
> > > - return x && (x & (x - 1));
> > > + return x && !(x & (x - 1));
> > > }
> >
> > I'm pretty sure we have this test in macro in includes somewhere... should we use
> > that instead?
>
> I went looking for a macro that provided this check and could not find one. I

arch/microblaze/mm/pgtable.c

#define is_power_of_2(x)	((x) != 0 && (((x) & ((x) - 1)) == 0))

> did find the inlined static function is_power_of_2 in log2.h, though, that we
> could use.

Here is a patch, but it seems that this is not worth the extra pain.

https://lore.kernel.org/bpf/8e5291b7-bd89-6fea-bfb7-954cacdb8523@xxxxxxxxxxxxx/

Thanks,
Tiezhu