Re: [PATCH v2 3/5] mm/memory_hotplug: use nth_page() in place of direct struct page manipulation.

From: Zi Yan <ziy@nvidia.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-mips@vger.kernel.org
Cc: Zi Yan <ziy@nvidia.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	"\"Matthew Wilcox (Oracle)\"" <willy@infradead.org>,
	David Hildenbrand <david@redhat.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Muchun Song <muchun.song@linux.dev>,
	"\"Mike Rapoport (IBM)\"" <rppt@kernel.org>,
	stable@vger.kernel.org, Muchun Song <songmuchun@bytedance.com>
Subject: Re: [PATCH v2 3/5] mm/memory_hotplug: use nth_page() in place of direct struct page manipulation.
Date: Wed, 06 Sep 2023 13:46:41 -0400	[thread overview]
Message-ID: <0B2678F2-9072-4C82-B233-11D74246FA8B@nvidia.com> (raw)
In-Reply-To: <20230906150309.114360-4-zi.yan@sent.com>

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On 6 Sep 2023, at 11:03, Zi Yan wrote:

> From: Zi Yan <ziy@nvidia.com>
>
> When dealing with hugetlb pages, manipulating struct page pointers
> directly can get to wrong struct page, since struct page is not guaranteed
> to be contiguous on SPARSEMEM without VMEMMAP. Use nth_page() to handle
> it properly.
>
> Fixes: eeb0efd071d8 ("mm,memory_hotplug: fix scan_movable_pages() for gigantic hugepages")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  mm/memory_hotplug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 1b03f4ec6fd2..3b301c4023ff 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1689,7 +1689,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
>  		 */
>  		if (HPageMigratable(head))
>  			goto found;
> -		skip = compound_nr(head) - (page - head);
> +		skip = compound_nr(head) - (pfn - page_to_pfn(head));
>  		pfn += skip - 1;
>  	}
>  	return -ENOENT;
> -- 
> 2.40.1

Fixed the subject and commit message:

From: Zi Yan <ziy@nvidia.com>
Date: Wed, 6 Sep 2023 10:51:21 -0400
Subject: [PATCH v2 3/5] mm/memory_hotplug: use pfn calculation in place of direct struct page manipulation.

When dealing with hugetlb pages, manipulating struct page pointers
directly can get to wrong struct page, since struct page is not guaranteed
to be contiguous on SPARSEMEM without VMEMMAP. Use pfn calculation to
handle it properly.

Fixes: eeb0efd071d8 ("mm,memory_hotplug: fix scan_movable_pages() for gigantic hugepages")
Cc: <stable@vger.kernel.org>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
 mm/memory_hotplug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1b03f4ec6fd2..3b301c4023ff 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1689,7 +1689,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
                 */
                if (HPageMigratable(head))
                        goto found;
-               skip = compound_nr(head) - (page - head);
+               skip = compound_nr(head) - (pfn - page_to_pfn(head));
                pfn += skip - 1;
        }
        return -ENOENT;
--
2.40.1


--
Best Regards,
Yan, Zi

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