Re: [linux-next:master] [mm] 0fa2857d23: WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof

[Yosry Ahmed]

[..]
> >>
> >> -       p->zeromap = bitmap_zalloc(maxpages, GFP_KERNEL);
> >> +       p->zeromap = kvzalloc(DIV_ROUND_UP(maxpages, 8), GFP_KERNEL);
> > No, 8 is not right for 32-bit kernels. I think you want
> >       p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages), GFP_KERNEL);
> > but please check it carefully, I'm easily confused by such conversions.
> >
> > Hugh
>
> Ah yes, didnt take into account 32-bit kernel. I think its supposed to be
>
>   p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages) * sizeof(unsigned long),
> GFP_KERNEL);

You can do something similar to bitmap_zalloc() and use:

kvmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long), GFP_KERNEL
| __GFP_ZERO)

I don't see a kvzalloc_array() variant to use directly, but it should
be trivial to add it. I can see other users of kvmalloc_array() that
pass in __GFP_ZERO (e.g. fs/ntfs3/bitmap.c).

, or you could take it a step further and add bitmap_kvzalloc(),
assuming the maintainers are open to that.

The main reason I want to avoid doing the multiplication inline is
because kvmalloc_array() has a check_mul_overflow() check, and I
assume it must have been added for a reason.