Re: [PATCH STABLE v6.1.y] mm/migrate: set swap entry values of THP tail pages properly.

[Zi Yan <ziy@nvidia.com>]

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On 5 Mar 2024, at 11:13, 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.

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 c93dd6a31c31..c5968021fde0 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -423,8 +423,12 @@ int folio_migrate_mapping(struct address_space *mapping,
>  	if (folio_test_swapbacked(folio)) {
>  		__folio_set_swapbacked(newfolio);
>  		if (folio_test_swapcache(folio)) {
> +			int i;
> +
>  			folio_set_swapcache(newfolio);
> -			newfolio->private = folio_get_private(folio);
> +			for (i = 0; i < nr; i++)
> +				set_page_private(folio_page(newfolio, i),
> +					page_private(folio_page(folio, i)));
>  		}
>  		entries = nr;
>  	} else {
> -- 
> 2.43.0


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Best Regards,
Yan, Zi

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