RE: [PATCH] mm/hmm: constify hmm_devmem_page_get_drvdata() parameter

[Ralph Campbell]

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@xxxxxxxxxxxxxxxxxxxx]
> Sent: Monday, October 2, 2017 2:41 PM
> To: Jérôme Glisse <jglisse@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; Ralph Campbell
> <rcampbell@xxxxxxxxxx>
> Subject: Re: [PATCH] mm/hmm: constify hmm_devmem_page_get_drvdata()
> parameter
> 
> On Mon,  2 Oct 2017 15:32:54 -0400 Jérôme Glisse <jglisse@xxxxxxxxxx>
> wrote:
> 
> > From: Ralph Campbell <rcampbell@xxxxxxxxxx>
> >
> > 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.