linux-kernel - Re: [PATCH 1/4] mm/gup_benchmark: Take the mmap lock around GUP

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Message-ID: <CANN689ESNEt7Ju0_jSVeP-37J+a0AvXsVRzNQ-s2cjM--AND+Q@mail.gmail.com>
Date:   Wed, 30 Sep 2020 16:21:09 -0700
From:   Michel Lespinasse <walken@...gle.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH 1/4] mm/gup_benchmark: Take the mmap lock around GUP

On Tue, Sep 29, 2020 at 6:20 PM Jann Horn <jannh@...gle.com> wrote:
> To be safe against concurrent changes to the VMA tree, we must take the
> mmap lock around GUP operations (excluding the GUP-fast family of
> operations, which will take the mmap lock by themselves if necessary).
>
> This code is only for testing, and it's only reachable by root through
> debugfs, so this doesn't really have any impact; however, if we want to add
> lockdep asserts into the GUP path, we need to have clean locking here.
>
> Signed-off-by: Jann Horn <jannh@...gle.com>

Acked-by: Michel Lespinasse <walken@...gle.com>

Thanks for these cleanups :)

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.