linux-kernel - Re: [PATCH 1/5] mm: Introduce mm_struct.has

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Message-ID: <CAHk-=whDSH_MRMt80JaSwoquzt=1nQ-0n3w0aVngoWPAc10BCw@mail.gmail.com>
Date:   Fri, 25 Sep 2020 14:06:59 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Xu <peterx@...hat.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Kirill Shutemov <kirill@...temov.name>,
        Hugh Dickins <hughd@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 1/5] mm: Introduce mm_struct.has_pinned

On Fri, Sep 25, 2020 at 12:56 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> And honestly, since this is all getting fairly late in the rc, and it
> took longer than I thought, I think we should do the GFP_ATOMIC
> approach for now - not great, but since it only triggers for this case
> that really should never happen anyway, I think it's probably the best
> thing for 5.9, and we can improve on things later.

I'm not super-happy with this patch, but I'm throwing it out anyway, in case

 (a) somebody can test it - I don't have any test cases

 (b) somebody can find issues and improve on it

but it's the simplest patch I can come up with for the small-page case.

I have *NOT* tested it. I have tried to think about it, and there are
more lines of comments than there are lines of code, but that only
means that if I didn't think about some case, it's neither in the
comments nor in the code.

I'm happy to take Peter's series too, this is more of an alternative
simplified version to keep the discussion going.

Hmm? What did I miss?

                     Linus

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