linux-kernel - Re: [PATCH v4 0/4] Make MIGRATE

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: <7AE9C2E9-2EC8-42E3-A3A5-3E4458796A51@nvidia.com>
Date: Tue, 20 May 2025 09:31:14 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, Oscar Salvador <osalvador@...e.de>,
 Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Mel Gorman <mgorman@...hsingularity.net>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Richard Chang <richardycc@...gle.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/4] Make MIGRATE_ISOLATE a standalone bit

On 20 May 2025, at 9:20, David Hildenbrand wrote:

>>> if a page gets freed while the pageblock is isolated, it cannot get added to the list of an owner easily.
>>
>> Right. In theory, it is possible, since when a MIGRATED_ISOLATE page is freed,
>> __free_one_page() can find its buddy and add the freed page to its buddy's
>> buddy_list without performing a merge like current code. But it needs a new
>> code path in __add_to_free_list(), since it is not added to the head nor the
>> tail of a free list.
>
> But what if the whole pageblock gets freed in a single shot (IOW, there is no buddy to lookup the list for?).

You are right. This means when MIGRATE_ISOLATE is removed, the global
MIGRATE_ISOLATE free list stays. BTW, looking at struct free_area,
its nr_free accounts for free pages in all migratetypes. Either struct free_area
stays the same or more code changes are needed to have isolated free list
+ !isolated free list. I will try to figure this out in the follow-up patchset.

--
Best Regards,
Yan, Zi