linux-kernel - Re: [PATCH 03/16] mm: add vma_desc_size(), vma_desc

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Message-ID: <20250908153342.GA789684@nvidia.com>
Date: Mon, 8 Sep 2025 12:33:42 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: David Hildenbrand <david@...hat.com>
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Subject: Re: [PATCH 03/16] mm: add vma_desc_size(), vma_desc_pages() helpers

On Mon, Sep 08, 2025 at 05:24:23PM +0200, David Hildenbrand wrote:
> > 
> > > I think we need to be cautious of scope here :) I don't want to
> > > accidentally break things this way.
> > 
> > IMHO it is worth doing when you get into more driver places it is far
> > more obvious why the VM_SHARED is being checked.
> > 
> > > OK I think a sensible way forward - How about I add desc_is_cowable() or
> > > vma_desc_cowable() and only set this if I'm confident it's correct?
> > 
> > I'm thinking to call it vma_desc_never_cowable() as that is much much
> > clear what the purpose is.
> 
> Secretmem wants no private mappings. So we should check exactly that, not
> whether we might have a cow mapping.

secretmem is checking shared for a different reason than many other places..

Jason