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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 17 Sep 2020 15:25:35 -0700
Message-ID: <CAHk-=wiXHrZsa+ATYSd2SxyKVY6=KWsj7_4Y2rhwEkt69hcWuA@mail.gmail.com>
Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Peter Xu <peterx@redhat.com>, John Hubbard <jhubbard@nvidia.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Maya B . Gokhale" <gokhale2@llnl.gov>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Marty Mcfadden <mcfadden8@llnl.gov>,
        Kirill Shutemov <kirill@shutemov.name>,
        Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
        Jan Kara <jack@suse.cz>, Kirill Tkhai <ktkhai@virtuozzo.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>
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On Thu, Sep 17, 2020 at 3:09 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> My advice for this -rc fix is to go with a single bit in the mm_struct
> set on any call to pin_user_pages*

Ack, except make sure it's a byte rather than a bitfield that could
have races. Or even just a separate atomic_t.

Keep it simple ans stupid and obvious. As you say, we can aim for
cleanups later, make it obvious and reliable right now.

             Linus