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

Aneesh Kumar K.V
2019-06-14T08:58:52Z

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.

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;
}

/*