Re: [v6 02/15] x86/mm: setting fields in deferred pages

Michal Hocko
2017-08-14T11:43:31Z

On Fri 11-08-17 11:39:41, Pasha Tatashin wrote:
> >AFAIU register_page_bootmem_info_node is only about struct pages backing
> >pgdat, usemap and memmap. Those should be in reserved memblocks and we
> >do not initialize those at later times, they are not relevant to the
> >deferred initialization as your changelog suggests so the ordering with
> >get_page_bootmem shouldn't matter. Or am I missing something here?
>
> The pages for pgdata, usemap, and memmap are part of reserved, and thus
> getting initialized when free_all_bootmem() is called.
>
> So, we have something like this in mem_init()
>
> register_page_bootmem_info
> register_page_bootmem_info_node
> get_page_bootmem
> .. setting fields here ..
> such as: page->freelist = (void *)type;
>
> free_all_bootmem()
> free_low_memory_core_early()
> for_each_reserved_mem_region()
> reserve_bootmem_region()
> init_reserved_page() <- Only if this is deferred reserved page
> __init_single_pfn()
> __init_single_page()
> memset(0) <-- Loose the set fields here!

OK, I have missed that part. Please make it explicit in the changelog.
It is quite easy to get lost in the deep call chains.
--
Michal Hocko
SUSE Labs