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

From: Charan Teja Kalla <quic_charante@quicinc.com>
To: Zi Yan <ziy@nvidia.com>, <gregkh@linuxfoundation.org>,
	<stable@vger.kernel.org>
Cc: <linux-mm@kvack.org>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	David Hildenbrand <david@redhat.com>,
	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 21:52:10 +0530	[thread overview]
Message-ID: <ce7f78bd-68ef-952e-ae6e-8cb2429d04a1@quicinc.com> (raw)
In-Reply-To: <F242A2B9-8791-4446-A35D-110A77919115@nvidia.com>

Thanks David for various inputs on this patch!!.

On 3/5/2024 9:47 PM, Zi Yan wrote:
> 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")
> 

Thanks Zi Yan, for posting this patch. I think below tag too applicable?

Closes:
https://lore.kernel.org/linux-mm/1707814102-22682-1-git-send-email-quic_charante@quicinc.com/

> 
>>
>> 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
> 
> 
> --
> Best Regards,
> Yan, Zi