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From:   Michel Lespinasse <walken@google.com>
Date:   Wed, 30 Sep 2020 16:24:39 -0700
Message-ID: <CANN689HPPP3kKNFpm5ymJhk-FODN1nXgMHouZ5-v1m=BJ+HyJg@mail.gmail.com>
Subject: Re: [PATCH 4/4] mm/gup: Assert that the mmap lock is held in __get_user_pages()
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>
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On Wed, Sep 30, 2020 at 5:32 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> On Tue, Sep 29, 2020 at 06:20:01PM -0700, Jann Horn wrote:
> > After having cleaned up all GUP callers (except for the atomisp staging
> > driver, which currently gets mmap locking completely wrong [1]) to always
> > ensure that they hold the mmap lock when calling into GUP (unless the mm is
> > not yet globally visible), add an assertion to make sure it stays that way
> > going forward.

Thanks for doing this, there is a lot of value in ensuring that a
function's callers follows the prerequisites.

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