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Message-ID: <b47ebf69-77eb-4a77-0fbc-631175aca979@redhat.com>
Date: Wed, 14 Aug 2019 18:09:16 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, Arun KS <arunks@...eaurora.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Oscar Salvador <osalvador@...e.de>,
Michal Hocko <mhocko@...e.com>,
Pavel Tatashin <pasha.tatashin@...een.com>,
Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 4/5] mm/memory_hotplug: Make sure the pfn is aligned to
the order when onlining
On 14.08.19 17:41, David Hildenbrand wrote:
> Commit a9cd410a3d29 ("mm/page_alloc.c: memory hotplug: free pages as higher
> order") assumed that any PFN we get via memory resources is aligned to
> to MAX_ORDER - 1, I am not convinced that is always true. Let's play safe,
> check the alignment and fallback to single pages.
>
> Cc: Arun KS <arunks@...eaurora.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
> mm/memory_hotplug.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 63b1775f7cf8..f245fb50ba7f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -646,6 +646,9 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
> */
> for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) {
> order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn)));
> + /* __free_pages_core() wants pfns to be aligned to the order */
> + if (unlikely(!IS_ALIGNED(pfn, 1ul << order)))
> + order = 0;
> (*online_page_callback)(pfn_to_page(pfn), order);
> }
>
>
@Michal, if you insist, we can drop this patch. "break first and fix
later" is not part of my DNA :)
--
Thanks,
David / dhildenb
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