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Date:   Tue, 9 Feb 2021 08:19:51 +0000
From:   Christoph Hellwig <hch@infradead.org>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Peter Xu <peterx@redhat.com>, dan.j.williams@intel.com,
        Paolo Bonzini <pbonzini@redhat.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn
Message-ID: <20210209081951.GA1704636@infradead.org>
References: <20210205103259.42866-1-pbonzini@redhat.com>
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 <20210208185133.GW4718@ziepe.ca>
 <20210208220259.GA71523@xz-x1>
 <20210208232625.GA4718@ziepe.ca>
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On Mon, Feb 08, 2021 at 07:26:25PM -0400, Jason Gunthorpe wrote:
> > > page_mkclean() has some technique to make the notifier have the right
> > > size without becoming entangled in the PTL locks..
> > 
> > Right.  I guess it's because dax doesn't have "struct page*" on the
> > back, so it
> 
> It doesn't? I thought DAX cases did?

File system DAX has a struct page, device DAX does not.  Which means
everything using iomap should have a page available, but i'm adding
Dan as he should know the details :)