linux-kernel - Re: [PATCH 1/9] mm, swap: use unified helper for swap cache look up

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAGsJ_4xoN35Av2H70o+dwGzhKrAnm7gppEseG0MgAUPQt2TygQ@mail.gmail.com>
Date: Tue, 2 Sep 2025 07:50:57 +0800
From: Barry Song <21cnbao@...il.com>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Matthew Wilcox <willy@...radead.org>, Hugh Dickins <hughd@...gle.com>, Chris Li <chrisl@...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>, 
	David Hildenbrand <david@...hat.com>, Yosry Ahmed <yosryahmed@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] mm, swap: use unified helper for swap cache look up

On Sat, Aug 23, 2025 at 3:20 AM Kairui Song <ryncsn@...il.com> wrote:
>
> From: Kairui Song <kasong@...cent.com>
>
> Always use swap_cache_get_folio for swap cache folio look up. The reason
> we are not using it in all places is that it also updates the readahead
> info, and some callsites want to avoid that.
>
> So decouple readahead update with swap cache lookup into a standalone
> helper, let the caller call the readahead update helper if that's
> needed. And convert all swap cache lookups to use swap_cache_get_folio.
>
> After this commit, there are only three special cases for accessing swap
> cache space now: huge memory splitting, migration and shmem replacing,
> because they need to lock the Xarray. Following commits will wrap their
> accesses to the swap cache too with special helpers.
>
> Signed-off-by: Kairui Song <kasong@...cent.com>

Nice! This has cleaned up the confusing mix of using
swap_cache_get_folio with VMA, filemap_get_entry,
swap_cache_get_folio without VMA, and filemap_get_folio.

Reviewed-by: Barry Song <baohua@...nel.org>

Do we have any potential "dropbehind" cases for anonymous folios?
I guess not for now.

__filemap_get_folio()
{
        if (folio_test_dropbehind(folio) && !(fgp_flags & FGP_DONTCACHE))
                folio_clear_dropbehind(folio);
}

Can we mention something about it in the changelog?

Best regards
Barry