linux-kernel - Re: [PATCH v1 00/15] mm: COW fixes part 2: reliable GUP pins of anonymous pages

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Message-ID: <d615d51d-8643-190e-9cc2-844a28a349cf@redhat.com>
Date:   Wed, 9 Mar 2022 09:00:21 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Nadav Amit <namit@...are.com>, Rik van Riel <riel@...riel.com>,
        Roman Gushchin <guro@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Donald Dutile <ddutile@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
        Liang Zhang <zhangliang5@...wei.com>,
        Pedro Gomes <pedrodemargomes@...il.com>,
        Oded Gabbay <oded.gabbay@...il.com>,
        Linux-MM <linux-mm@...ck.org>,
        Khalid Aziz <khalid.aziz@...cle.com>
Subject: Re: [PATCH v1 00/15] mm: COW fixes part 2: reliable GUP pins of
 anonymous pages

On 08.03.22 22:22, Linus Torvalds wrote:
> On Tue, Mar 8, 2022 at 6:14 AM David Hildenbrand <david@...hat.com> wrote:
>>
>> This series fixes memory corruptions when a GUP pin (FOLL_PIN) was taken
>> on an anonymous page and COW logic fails to detect exclusivity of the page
>> to then replacing the anonymous page by a copy in the page table [...]
> 
> From a cursory scan of the patches, this looks sane.

Thanks for skimming over the patches that quickly!

> 
> I'm not sure what the next step should be, but I really would like the
> people who do a lot of pinning stuff to give it a good shake-down.
> Including both looking at the patches, but very much actually running
> it on whatever test-cases etc you people have.
> 
> Please?

My proposal would be to pull it into -next early after we have
v5.18-rc1. I expect some minor clashes with folio changes that should go
in in the next merge window, so I'll have to rebase+resend either way,
and I'm planning on thoroughly testing at least on s390x as well.

We'd then have plenty of time to further review+test while in -next
until the v5.19 merge window opens up.

By that time I should also have my selftests cleaned up and ready, and
part 3 ready to improve the situation for FOLL_GET|FOLL_WRITE until we
have the full FOLL_GET->FOLL_PIN conversion from John (I'll most
probably sent out an early RFC of part 3 soonish). So we *might* be able
to have everything fixed in v5.19.

Last but not least, tools/cgroup/memcg_slabinfo.py as mentioned in patch
#10 still needs care due to the PG_slab reuse, but I consider that a
secondary concern (yet, it should be fixed and help from the Authors
would be appreciated ;) ).

-- 
Thanks,

David / dhildenb