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Date:   Wed, 12 Jun 2019 04:23:50 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Thomas =?iso-8859-1?Q?Hellstr=F6m_=28VMware=29?= 
        <thellstrom@vmwopensource.org>
Cc:     dri-devel@lists.freedesktop.org,
        linux-graphics-maintainer@vmware.com, pv-drivers@vmware.com,
        linux-kernel@vger.kernel.org, nadav.amit@gmail.com,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Will Deacon <will.deacon@arm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Rik van Riel <riel@surriel.com>,
        Minchan Kim <minchan@kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        Huang Ying <ying.huang@intel.com>,
        Souptick Joarder <jrdr.linux@gmail.com>,
        =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
        linux-mm@kvack.org, Ralph Campbell <rcampbell@nvidia.com>
Subject: Re: [PATCH v5 3/9] mm: Add write-protect and clean utilities for
 address space ranges
Message-ID: <20190612112349.GA20226@infradead.org>
References: <20190612064243.55340-1-thellstrom@vmwopensource.org>
 <20190612064243.55340-4-thellstrom@vmwopensource.org>
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On Wed, Jun 12, 2019 at 08:42:37AM +0200, Thomas Hellstr?m (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@vmware.com>
> 
> Add two utilities to a) write-protect and b) clean all ptes pointing into
> a range of an address space.
> The utilities are intended to aid in tracking dirty pages (either
> driver-allocated system memory or pci device memory).
> The write-protect utility should be used in conjunction with
> page_mkwrite() and pfn_mkwrite() to trigger write page-faults on page
> accesses. Typically one would want to use this on sparse accesses into
> large memory regions. The clean utility should be used to utilize
> hardware dirtying functionality and avoid the overhead of page-faults,
> typically on large accesses into small memory regions.

Please use EXPORT_SYMBOL_GPL, just like for apply_to_page_range and
friends.  Also in general new core functionality like this should go
along with the actual user, we don't need to repeat the hmm disaster.