Re: [PATCH STABLE v5.4.y] mm/migrate: set swap entry values of THP tail pages properly.

[David Hildenbrand <david@redhat.com>]

On 05.03.24 17:29, Zi Yan wrote:
> From: Zi Yan <ziy@nvidia.com>
> 
> The tail pages in a THP can have swap entry information stored in their
> private field. When migrating to a new page, all tail pages of the new
> page need to update ->private to avoid future data corruption.
> 
> Corresponding swapcache entries need to be updated as well.
> e71769ae5260 ("mm: enable thp migration for shmem thp") fixed it already.
> 
> Closes: https://lore.kernel.org/linux-mm/1707814102-22682-1-git-send-email-quic_charante@quicinc.com/
> Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path")
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>   mm/migrate.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 034b0662fd3b..9cfd53eaeb4e 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -441,8 +441,12 @@ int migrate_page_move_mapping(struct address_space *mapping,
>   	if (PageSwapBacked(page)) {
>   		__SetPageSwapBacked(newpage);
>   		if (PageSwapCache(page)) {
> +			int i;
> +
>   			SetPageSwapCache(newpage);
> -			set_page_private(newpage, page_private(page));
> +			for (i = 0; i < (1 << compound_order(page)); i++)
> +				set_page_private(newpage + i,
> +						 page_private(page + i));
>   		}
>   	} else {
>   		VM_BUG_ON_PAGE(PageSwapCache(page), page);

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb