Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()

Qian Cai
2019-06-14T14:59:29Z

On Fri, 2019-06-14 at 14:28 +0530, Aneesh Kumar K.V wrote:
> Qian Cai <cai@lca.pw> writes:
>
>
> > 1) offline is busted [1]. It looks like test_pages_in_a_zone() missed the
> > same
> > pfn_section_valid() check.
> >
> > 2) powerpc booting is generating endless warnings [2]. In
> > vmemmap_populated() at
> > arch/powerpc/mm/init_64.c, I tried to change PAGES_PER_SECTION to
> > PAGES_PER_SUBSECTION, but it alone seems not enough.
> >
>
> Can you check with this change on ppc64.  I haven't reviewed this series yet.
> I did limited testing with change . Before merging this I need to go
> through the full series again. The vmemmap poplulate on ppc64 needs to
> handle two translation mode (hash and radix). With respect to vmemap
> hash doesn't setup a translation in the linux page table. Hence we need
> to make sure we don't try to setup a mapping for a range which is
> arleady convered by an existing mapping.

It works fine.

>
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index a4e17a979e45..15c342f0a543 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -88,16 +88,23 @@ static unsigned long __meminit
> vmemmap_section_start(unsigned long page)
>   * which overlaps this vmemmap page is initialised then this page is
>   * initialised already.
>   */
> -static int __meminit vmemmap_populated(unsigned long start, int page_size)
> +static bool __meminit vmemmap_populated(unsigned long start, int page_size)
>  {
>   unsigned long end = start + page_size;
>   start = (unsigned long)(pfn_to_page(vmemmap_section_start(start)));
>
> - for (; start < end; start += (PAGES_PER_SECTION * sizeof(struct
> page)))
> - if (pfn_valid(page_to_pfn((struct page *)start)))
> - return 1;
> + for (; start < end; start += (PAGES_PER_SECTION * sizeof(struct
> page))) {
>
> - return 0;
> + struct mem_section *ms;
> + unsigned long pfn = page_to_pfn((struct page *)start);
> +
> + if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> + return 0;
> + ms = __nr_to_section(pfn_to_section_nr(pfn));
> + if (valid_section(ms))
> + return true;
> + }
> + return false;
>  }
>
>  /*
>