Re: [PATCH v2 16/18] memblock: make HugeTLB bootmem allocation work with KHO

[Mike Rapoport <rppt@kernel.org>]

On Mon, Jun 15, 2026 at 03:35:39PM +0200, Pratyush Yadav wrote:
> On Sun, Jun 14 2026, Mike Rapoport wrote:
> > On Fri, 05 Jun 2026 20:34:49 +0200, Pratyush Yadav <pratyush@kernel.org> wrote:
> >
> >> First, it does not use mirrored memory for hugetlb. Mirrored memory is a
> >> limited resource that is best saved for kernel data structures, not user
> >> memory.
> >> 
> >> Second, if the memory found overlaps with KHO scratch areas, it discards
> >> the memory and retries.
> >
> > This sentence is somewhat hard to parse.
> 
> Okay, let me retry:
> 
>     Second, if the free memory area found by memblock_find_in_range_node()
>     is a part of a KHO scratch area, the free area is not used. Allocation
>     is retried starting after the free area to ensure no hugepages come from
>     KHO scratch.
> 
> Any better?

Yep :)
 
> >
> >>
> >>
> >> diff --git a/mm/memblock.c b/mm/memblock.c
> >> index 6349c48154f4..131e54dd5d8d 100644
> >> --- a/mm/memblock.c
> >> +++ b/mm/memblock.c
> >> @@ -1756,6 +1761,69 @@ void * __init memblock_alloc_try_nid_raw(
> >> [ ... skip 51 lines ... ]
> >> +		if (memblock_bottom_up())
> >> +			start = addr + size;
> >> +		else
> >> +			start = addr - size;
> >> +
> >> +		goto retry;
> >
> > Hmm, two goto retry don't seem nice :/
> > Although I can't see how to imporove it really.
> 
> Dunno, looked easy enough to understand to me.
> >
> > Maybe add a helper for going the node fallback?
> 
> There is a small downside. There will then be no way to know the
> fallback was tried already, so if a retry is done because of scratch
> overlap, the fallback needs to be done again.
> 
> I don't think it should be too bad, so if you still prefer this then I
> can do it.

Let's keep it for now, maybe will find something smarter later.
 
> -- 
> Regards,
> Pratyush Yadav

-- 
Sincerely yours,
Mike.