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

Oscar Salvador
2019-06-14T15:35:45Z

On Fri, Jun 14, 2019 at 02:28:40PM +0530, Aneesh Kumar K.V wrote:
> 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.
>
> 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;

I might be missing something, but is this right?
Having a section_nr above NR_MEM_SECTIONS is invalid, but if we return 0 here,
vmemmap_populate will go on and populate it.

--
Oscar Salvador
SUSE L3