linux-kernel - Re: [PATCH mm-new v2 1/1] mm/khugepaged: abort collapse scan on non-swap entries

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 for Android: free password hash cracker in your pocket

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

Message-ID: <1c2fae79-69ad-45c2-8da7-31b3cd6dcda0@redhat.com>
Date: Wed, 8 Oct 2025 11:00:09 +0200
From: David Hildenbrand <david@...hat.com>
To: Lance Yang <lance.yang@...ux.dev>, Wei Yang <richard.weiyang@...il.com>
Cc: akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, baohua@...nel.org, baolin.wang@...ux.alibaba.com,
 dev.jain@....com, hughd@...gle.com, ioworker0@...il.com,
 kirill@...temov.name, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 mpenttil@...hat.com, npache@...hat.com, ryan.roberts@....com, ziy@...dia.com
Subject: Re: [PATCH mm-new v2 1/1] mm/khugepaged: abort collapse scan on
 non-swap entries

> Second, as Wei pointed out[3], we may have a chance to get a non-swap
> entry, since we will drop and re-acquire the mmap lock before
> __collapse_huge_page_swapin(). To handle this, we also add a
> non_swap_entry() check there.
> 
> Note that we can unlock later what we really need, and not account it
> towards max_swap_ptes.
> 
> [1]
> https://lore.kernel.org/linux-mm/09eaca7b-9988-41c7-8d6e-4802055b3f1e@redhat.com
> [2]
> https://lore.kernel.org/linux-mm/7df49fe7-c6b7-426a-8680-dcd55219c8bd@lucifer.local
> [3] https://lore.kernel.org/linux-mm/20251005010511.ysek2nqojebqngf3@master
> ```
> 

I replied to the new version.

> I also think it makes sense to fold the change that adds the
> non_swap_entry() check in __collapse_huge_page_swapin() into
> this patch, rather than creating a new patch just for that :)
> 
> Hmmm... one thing I'm not sure about: regarding the uffd-wp
> race you mentioned, is the pte_swp_uffd_wp() check needed
> after non_swap_entry()? It seems like it might not be ...
> 

If we check non_swap_entry(), there is no need to check for other 
markers, agreed.

-- 
Cheers

David / dhildenb