linux-kernel - Re: [PATCH 08/16] mm: add remap_pfn_range_prepare(), remap_pfn_range

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Message-ID: <0645c8bf-4d5d-4740-beab-10157d133725@lucifer.local>
Date: Mon, 8 Sep 2025 17:07:12 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
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Subject: Re: [PATCH 08/16] mm: add remap_pfn_range_prepare(),
 remap_pfn_range_complete()

On Mon, Sep 08, 2025 at 01:03:06PM -0300, Jason Gunthorpe wrote:
> On Mon, Sep 08, 2025 at 03:18:46PM +0100, Lorenzo Stoakes wrote:
> > On Mon, Sep 08, 2025 at 10:35:38AM -0300, Jason Gunthorpe wrote:
> > > On Mon, Sep 08, 2025 at 02:27:12PM +0100, Lorenzo Stoakes wrote:
> > >
> > > > It's not only remap that is a concern here, people do all kinds of weird
> > > > and wonderful things in .mmap(), sometimes in combination with remap.
> > >
> > > So it should really not be split this way, complete is a badly name
> >
> > I don't understand, you think we can avoid splitting this in two? If so, I
> > disagree.
>
> I'm saying to the greatest extent possible complete should only
> populate PTEs.
>
> We should refrain from trying to use it for other things, because it
> shouldn't need to be there.

OK that sounds sensible, I will refactor to try to do only this in the
mmap_complete hook as far as is possible and see if I can use a generic function
also.

>
> > > The only example in this series didn't actually need to hold the lock.
> >
> > There's ~250 more mmap callbacks to work through. Do you provide a guarantee
> > that:
>
> I'd be happy if only a small few need something weird and everything
> else was aligned.

Ack!

>
> Jason

Cheers, Lorenzo