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Subject: Re: [PATCH v4 1/1] mm: introduce put_user_page*(), placeholder
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From:   William Kucharski <william.kucharski@oracle.com>
In-Reply-To: <20190320043319.GA7431@redhat.com>
Date:   Wed, 20 Mar 2019 08:55:17 -0600
Cc:     John Hubbard <jhubbard@nvidia.com>,
        Dave Chinner <david@fromorbit.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        john.hubbard@gmail.com, Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
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        Christian Benvenuti <benve@cisco.com>,
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        Ira Weiny <ira.weiny@intel.com>, Jan Kara <jack@suse.cz>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Matthew Wilcox <willy@infradead.org>,
        Michal Hocko <mhocko@kernel.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Mike Marciniszyn <mike.marciniszyn@intel.com>,
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        Tom Talpey <tom@talpey.com>,
        LKML <linux-kernel@vger.kernel.org>,
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        Andrea Arcangeli <aarcange@redhat.com>
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To:     Jerome Glisse <jglisse@redhat.com>
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> On Mar 19, 2019, at 10:33 PM, Jerome Glisse <jglisse@redhat.com> wrote:
> 
> So i believe best we could do is send a SIGBUS to the process that has
> GUPed a range of a file that is being truncated this would match what
> we do for CPU acces. There is no reason access through GUP should be
> handled any differently.

This should be done lazily, as there's no need to send the SIGBUS unless
the GUPed page is actually accessed post-truncate.