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Date:   Fri, 28 Jan 2022 11:30:10 +0800
From:   Peter Xu <peterx@redhat.com>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Jan Kara <jack@suse.cz>,
        =?utf-8?B?SsOpcsO0bWU=?= Glisse <jglisse@redhat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH] mm: Fix invalid page pointer returned with FOLL_PIN gups
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References: <20220125033700.69705-1-peterx@redhat.com>
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On Thu, Jan 27, 2022 at 06:32:27PM -0800, John Hubbard wrote:
> What you are missing is that other people are potentially writing code
> that we haven't seen yet, and that code may use follow_page_mask(). The
> idea, therefore, is to make it a good building block.

Yes, actually that's why I attached the WARN_ON_ONCE() since when people do add
that new code they'll quickly discover before posting, as long as they'll still
test the patch..

Then people may even start to wonder whether we should rework -EEXIST if
necessary, and IMHO that's the better place for a rework, not within the bugfix
here.

Please check the email I replied to Jason.  I hope both of you would agree that
I can repost with the fix only but drop the WARN_ON_ONCE(), or any explicit
suggestion on how we should move forward with the fix would be welcomed.

Thanks,

-- 
Peter Xu