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Message-ID: <acdf3d44-b20e-8491-6302-bfb1b354bc62@quicinc.com>
Date: Wed, 28 Feb 2024 21:06:19 +0530
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Subject: Re: [PATCH] mm/huge_memory: fix swap entry values of tail pages of
 THP
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To: Zi Yan <ziy@nvidia.com>, David Hildenbrand <david@redhat.com>
CC: Matthew Wilcox <willy@infradead.org>, <gregkh@linuxfoundation.org>,
        <akpm@linux-foundation.org>, <vbabka@suse.cz>, <dhowells@redhat.com>,
        <surenb@google.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        #
 see patch description <stable@vger.kernel.org>,
        Huang Ying
	<ying.huang@intel.com>,
        Naoya Horiguchi <naoya.horiguchi@linux.dev>
References: <1707814102-22682-1-git-send-email-quic_charante@quicinc.com>
 <a683e199-ce8a-4534-a21e-65f2528415a6@redhat.com>
 <8620c1a0-e091-46e9-418a-db66e621b9c4@quicinc.com>
 <845ca78f-913b-4a92-8b40-ff772a7ad333@redhat.com>
 <bc1a5e36-1983-1a39-4d06-8062993a4ca4@quicinc.com>
 <ZczLoOqdpMJpkO5N@casper.infradead.org>
 <f2ad5918-7e36-4a7c-a619-c6807cfca5ec@redhat.com>
 <30ea073d-0ccf-46e1-954d-e22f5cbf69f7@redhat.com>
 <1ABD022A-35FC-4A6E-ADAD-36F3D745FB91@nvidia.com>
 <42be658c-cb13-4001-aae4-8d8275a84038@redhat.com>
 <ECEF5EF8-3328-43AD-9E0B-7AE325368CB7@nvidia.com>
 <07A26237-B17E-4418-9A19-E86F450B9695@nvidia.com>
From: Charan Teja Kalla <quic_charante@quicinc.com>
In-Reply-To: <07A26237-B17E-4418-9A19-E86F450B9695@nvidia.com>
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Thanks David/Zi Yan,

On 2/27/2024 9:45 PM, Zi Yan wrote:
> So likely we'd have to fix the stable kernels:
> 
> 4.19
> 5.4
> 5.10
> 5.15
> 6.1
> 
> That's a lot of pre-folio code. A backport of my series likely won't really make any sense.

So, I assume this is a consensus to have stable-only fix for this issue.

> 
> For v6.1, the fix would like below?
> 
> 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 {

Similar to this is what we had tested[1] internally and observed no issues.

Can this be taken to 6.1, please?

[1]https://lore.kernel.org/linux-mm/8620c1a0-e091-46e9-418a-db66e621b9c4@quicinc.com/

Thanks,
Charan