linux-kernel - Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow

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Message-ID: <abcace40-d691-a630-a751-f52f24f832fe@oracle.com>
Date:   Tue, 9 Feb 2021 10:02:11 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Peter Xu <peterx@...hat.com>, dan.j.williams@...el.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn

On 2/9/21 8:19 AM, Christoph Hellwig wrote:
> 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 :)
> 
Both fsdax and device-dax have struct page. It's the pmem block device
that doesn't.