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

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Message-ID: <20250908160306.GF789684@nvidia.com>
Date: Mon, 8 Sep 2025 13:03:06 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.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 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.

> > 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.

Jason