Re: [v6 00/15] complete deferred page initialization

Michal Hocko
2017-08-11T15:22:46Z

On Fri 11-08-17 11:13:07, Pasha Tatashin wrote:
> On 08/11/2017 03:58 AM, Michal Hocko wrote:
> >[I am sorry I didn't get to your previous versions]
>
> Thank you for reviewing this work. I will address your comments, and
> send-out a new patches.
>
> >>
> >>In this work we do the following:
> >>- Never read access struct page until it was initialized
> >
> >How is this enforced? What about pfn walkers? E.g. page_ext
> >initialization code (page owner in particular)
>
> This is hard to enforce 100%. But, because we have a patch in this series
> that sets all memory that was allocated by memblock_virt_alloc_try_nid_raw()
> to ones with debug options enabled, and because Linux has a good set of
> asserts in place that check struct pages to be sane, especially the ones
> that are enabled with this config: CONFIG_DEBUG_VM_PGFLAGS. I was able to
> find many places in linux which accessed struct pages before
> __init_single_page() is performed, and fix them. Most of these places happen
> only when deferred struct page initialization code is enabled.

Yes, I am very well aware of how hard is this to guarantee. I was merely
pointing out that the changelog should be more verbose about your
testing and assumptions so that we can revalidate them.
--
Michal Hocko
SUSE Labs