Re: [PATCH] mm: use early_pfn_to_nid in register_page_bootmem_info_node

From: Shi, Yang
Date: Wed May 25 2016 - 19:44:55 EST

On 5/25/2016 3:23 PM, Andrew Morton wrote:
On Wed, 25 May 2016 14:00:07 -0700 Yang Shi <yang.shi@xxxxxxxxxx> wrote:

register_page_bootmem_info_node() is invoked in mem_init(), so it will be
called before page_alloc_init_late() if CONFIG_DEFERRED_STRUCT_PAGE_INIT
is enabled. But, pfn_to_nid() depends on memmap which won't be fully setup
until page_alloc_init_late() is done, so replace pfn_to_nid() by

What are the runtime effects of this fix?

I didn't experience any problem without the fix. During working on the page_ext_init() fix (replace to early_pfn_to_nid()), I added printk before each pfn_to_nid() calls to check which one might be called before page_alloc_init_late(), then this one is caught.

From the code perspective, it sounds not right since register_page_bootmem_info_section() may miss some pfns when CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, just like the problem happened in page_ext_init().