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From: Ralph Campbell <rcampbell@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>,
        =?iso-8859-1?Q?J=E9r=F4me_Glisse?= <jglisse@redhat.com>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: RE: [PATCH] mm/hmm: constify hmm_devmem_page_get_drvdata() parameter
Thread-Topic: [PATCH] mm/hmm: constify hmm_devmem_page_get_drvdata() parameter
Thread-Index: AQHTO63NsfPm9K2GWkCGrnqsc+sJFaLRFtUAgAAB6PA=
Date: Mon, 2 Oct 2017 21:54:43 +0000
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The use case is when called by struct hmm_devmem_ops.fault() which passes a const struct page * pointer and hmm_devmem_page_get_drvdata() is called to get the private data.
Since HMM was only recently added, it only affects kernels after September 8, 2017.

> -----Original Message-----
> From: Andrew Morton [mailto:akpm@linux-foundation.org]
> Sent: Monday, October 2, 2017 2:41 PM
> To: Jérôme Glisse <jglisse@redhat.com>
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org; Ralph Campbell
> <rcampbell@nvidia.com>
> Subject: Re: [PATCH] mm/hmm: constify hmm_devmem_page_get_drvdata()
> parameter
> 
> On Mon,  2 Oct 2017 15:32:54 -0400 Jérôme Glisse <jglisse@redhat.com>
> wrote:
> 
> > From: Ralph Campbell <rcampbell@nvidia.com>
> >
> > Constify pointer parameter to avoid issue when use from code that only
> > has const struct page pointer to use in the first place.
> 
> That's rather vague.  Does such calling code exist in the kernel?  This affects the
> which-kernel-gets-patched decision.