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SubjectRe: [PATCH 0/6] mm: make movable onlining suck less
On Mon, Apr 03, 2017 at 10:23:38PM +0200, Michal Hocko wrote:
>On Mon 03-04-17 14:58:30, Reza Arbab wrote:
>> However, I am seeing a regression. When adding memory to a memoryless
>> node, it shows up in node 0 instead. I'm digging to see if I can help
>> narrow down where things go wrong.
>
>OK, I guess I know what is going on here. online_pages relies on
>pfn_to_nid(pfn) to return a proper node. But we are doing
>page_to_nid(pfn_to_page(__pfn_to_nid_pfn)) so we rely on the page being
>properly initialized. Damn, I should have noticed that. There are two
>ways around that. Either the __add_section stores the nid into the
>struct page and make page_to_nid reliable or store it somewhere else
>(ideally into the memblock). The first is easier (let's do it for now)
>but longterm we do not want to rely on the struct page at all I believe.
>
>Does the following help?
>---
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index b9dc1c4e26c3..0e21b9f67c9d 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -309,14 +309,19 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn)
>
> /*
> * Make all the pages reserved so that nobody will stumble over half
>- * initialized state.
>+ * initialized state.
>+ * FIXME: We also have to associate it with a node because pfn_to_node
>+ * relies on having page with the proper node.
> */
> for (i = 0; i < PAGES_PER_SECTION; i++) {
> unsigned long pfn = phys_start_pfn + i;
>+ struct page *page;
> if (!pfn_valid(pfn))
> continue;
>
>- SetPageReserved(pfn_to_page(phys_start_pfn + i));
>+ page = pfn_to_page(pfn);
>+ set_page_node(page, nid);
>+ SetPageReserved(page);
> }
>
> return register_new_memory(nid, __pfn_to_section(phys_start_pfn));

Almost there. I'm seeing the memory in the correct node now, but the
/sys/devices/system/node/nodeX/memoryY links are not being created.

I think it's tripping up here, in register_mem_sect_under_node():

page_nid = get_nid_for_pfn(pfn);
if (page_nid < 0)
continue;

--
Reza Arbab

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