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

From: David Hildenbrand <david@redhat.com>
To: Zi Yan <ziy@nvidia.com>,
	gregkh@linuxfoundation.org, stable@vger.kernel.org
Cc: linux-mm@kvack.org, Charan Teja Kalla <quic_charante@quicinc.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Huang Ying <ying.huang@intel.com>,
	Naoya Horiguchi <naoya.horiguchi@linux.dev>
Subject: Re: [PATCH STABLE v6.1.y] mm/migrate: set swap entry values of THP tail pages properly.
Date: Tue, 5 Mar 2024 17:22:07 +0100	[thread overview]
Message-ID: <58812e2d-8f81-4760-aa6a-7a0fbe42170e@redhat.com> (raw)
In-Reply-To: <20240305161313.90954-1-zi.yan@sent.com>

On 05.03.24 17:13, 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.
> 
> 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 {

Hopefully Charan can run the reproducer against this.

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

-- 
Cheers,

David / dhildenb