linux-kernel - Re: [PATCH v3 10/15] mm, swap: wrap swap cache replacement with a helper

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Message-ID: <e21cd2ba-9061-4c6c-9956-23db8be5e16c@redhat.com>
Date: Fri, 12 Sep 2025 18:06:11 +0200
From: David Hildenbrand <david@...hat.com>
To: Kairui Song <ryncsn@...il.com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Matthew Wilcox <willy@...radead.org>, Hugh Dickins <hughd@...gle.com>,
 Chris Li <chrisl@...nel.org>, Barry Song <baohua@...nel.org>,
 Baoquan He <bhe@...hat.com>, Nhat Pham <nphamcs@...il.com>,
 Kemeng Shi <shikemeng@...weicloud.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Ying Huang <ying.huang@...ux.alibaba.com>,
 Johannes Weiner <hannes@...xchg.org>, Yosry Ahmed <yosryahmed@...gle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>,
 linux-kernel@...r.kernel.org, Kairui Song <kasong@...cent.com>
Subject: Re: [PATCH v3 10/15] mm, swap: wrap swap cache replacement with a
 helper

On 10.09.25 18:08, Kairui Song wrote:
> From: Kairui Song <kasong@...cent.com>
> 
> There are currently three swap cache users that are trying to replace an
> existing folio with a new one: huge memory splitting, migration, and
> shmem replacement. What they are doing is quite similar.
> 
> Introduce a common helper for this. In later commits, this can be easily
> switched to use the swap table by updating this helper.
> 
> The newly added helper also makes the swap cache API better defined, and
> make debugging easier by adding a few more debug checks.
> 
> Migration and shmem replace are meant to clone the folio, including
> content, swap entry value, and flags. And splitting will adjust each
> sub folio's swap entry according to order, which could be non-uniform in
> the future. So document it clearly that it's the caller's responsibility
> to set up the new folio's swap entries and flags before calling the helper.
> The helper will just follow the new folio's entry value.
> 
> This also prepares for replacing high-order folios in the swap cache.
> Currently, only splitting to order 0 is allowed for swap cache folios.
> Using the new helper, we can handle high-order folio splitting better.
> 
> Signed-off-by: Kairui Song <kasong@...cent.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---

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

-- 
Cheers

David / dhildenb