linux-kernel - Re: [RFC PATCH v2 3/3] mm: mlock: update mlock_pte

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: <16844254-7248-f557-b1eb-b8b102c877a2@intel.com>
Date:   Mon, 17 Jul 2023 09:58:39 +0800
From:   Yin Fengwei <fengwei.yin@...el.com>
To:     Yu Zhao <yuzhao@...gle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <akpm@...ux-foundation.org>, <willy@...radead.org>,
        <david@...hat.com>, <ryan.roberts@....com>, <shy828301@...il.com>
Subject: Re: [RFC PATCH v2 3/3] mm: mlock: update mlock_pte_range to handle
 large folio



On 7/17/23 08:35, Yu Zhao wrote:
> On Sun, Jul 16, 2023 at 6:00 PM Yin, Fengwei <fengwei.yin@...el.com> wrote:
>>
>> On 7/15/2023 2:06 PM, Yu Zhao wrote:
>>> There is a problem here that I didn't have the time to elaborate: we
>>> can't mlock() a folio that is within the range but not fully mapped
>>> because this folio can be on the deferred split queue. When the split
>>> happens, those unmapped folios (not mapped by this vma but are mapped
>>> into other vmas) will be stranded on the unevictable lru.
>>
>> This should be fine unless I missed something. During large folio split,
>> the unmap_folio() will be migrate(anon)/unmap(file) folio. Folio will be
>> munlocked in unmap_folio(). So the head/tail pages will be evictable always.
> 
> It's close but not entirely accurate: munlock can fail on isolated folios.
Yes. The munlock just clear PG_mlocked bit but with PG_unevictable left.

Could this also happen against normal 4K page? I mean when user try to munlock
a normal 4K page and this 4K page is isolated. So it become unevictable page?


Regards
Yin, Fengwei