On Mon 19-02-18 12:06:14, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
>
> struct page is inizialized as zero in __init_single_page().
> If the page is offlined page, PG_reserved flag is set in early boot
> time before __init_single_page(), so we should not clear the flag.
>
> The real problem is that we can not online the offlined page
> through following sysfs operation because offlined page is
> expected PG_reserved flag is set.
> It is not needed the initialization, so remove it simply.
>
> Code:
>
> static int online_pages_range(unsigned long start_pfn,
> ...
> if (PageReserved(pfn_to_page(start_pfn))) <= HERE!!
> for (i = 0; i < nr_pages; i++) {
> page = pfn_to_page(start_pfn + i);
> (*online_page_callback)(page);
> onlined_pages++;
> sysfs operation:
>
> # echo online > /sys/devices/system/node/node2/memory12288/online
> # cat /sys/devices/system/node/node2/memory12288/online
> 1
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal: 0 kB
Nack. The patch is simply wrong. We do need to zero page for the boot
pages. I believe the fix you are looking for is 9bb5a391f9a5 ("mm,
memory_hotplug: fix memmap initialization"). Or do you still see a
problem with this patch applied?
> Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
> ---
> mm/page_alloc.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 76c9688..3260cd2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1179,7 +1179,6 @@ static void free_one_page(struct zone *zone,
> static void __meminit __init_single_page(struct page *page, unsigned long pfn,
> unsigned long zone, int nid)
> {
> - mm_zero_struct_page(page);
> set_page_links(page, zone, nid, pfn);
> init_page_count(page);
> page_mapcount_reset(page);
> --
> 2.16.1
>
> - Masayoshi
--
Michal Hocko
SUSE Labs
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