Re: [PATCH] Revert "mm/page_alloc: fix memmap_init_zone pageblock alignment"

[Michal Hocko]

On Wed 14-03-18 14:35:12, Ard Biesheuvel wrote:
> On 14 March 2018 at 14:13, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> > Does http://lkml.kernel.org/r/20180313224240.25295-1-neelx@xxxxxxxxxx
> > fix your issue? From the debugging info you provided it should because
> > the patch prevents jumping backwards.
> >
> 
> The patch does fix the boot hang.
> 
> But I am concerned that we are papering over a fundamental flaw in
> memblock_next_valid_pfn().

It seems that memblock_next_valid_pfn is doing the right thing here. It
is the alignment which moves the pfn back AFAICS. I am not really
impressed about the original patch either, to be completely honest.
It just looks awfully tricky. I still didn't manage to wrap my head
around the original issue though so I do not have much better ideas to
be honest.
-- 
Michal Hocko
SUSE Labs