linux-kernel - Re: [PATCH v2 0/4] mm: Break COW for pinned pages during fork()

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Date:   Sun, 27 Sep 2020 12:35:59 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Xu <peterx@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, Yang Shi <shy828301@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Kirill Shutemov <kirill@...temov.name>,
        Hugh Dickins <hughd@...gle.com>, Jann Horn <jannh@...gle.com>,
        Michal Hocko <mhocko@...e.com>, Jan Kara <jack@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH v2 0/4] mm: Break COW for pinned pages during fork()

On Fri, Sep 25, 2020 at 3:26 PM Peter Xu <peterx@...hat.com> wrote:
>
> This series is majorly inspired by the previous discussion on the list [1],
> starting from the report from Jason on the rdma test failure.

Ok, this is now in my git tree with the changes I outlined in the other email.

> I tested it myself with fork() after vfio pinning a bunch of device pages,

.. but _my_ only testing was to just add a nasty hack that said that
all pages are pinned, and made fork() much slower, but hey, it at
least tests the preallocation paths etc. And I'm not seeing any
obvious failures due to taking that slow-path that is supposed to be a
special case.

Let's hope this closes the rdma issues.

                Linus