Re: [PATCH v3 03/15] mm: abstract vma_address() and introduce vma_anon_address()

On Thu, Jul 30, 2026 at 12:58:22AM -0400, Gregory Price wrote:
> On Wed, Jul 29, 2026 at 05:48:38PM +0100, Lorenzo Stoakes (ARM) wrote:
> > 
> > This will be necessary for determining the address of a folio's index
> > within a VMA when the folio belongs to a MAP_PRIVATE file-backed VMA but
> > has been CoW'd, and thus is anonymous, once the anonymous VMA page offset
> > field is used for the reverse mapping.
> > 
> 
> This is a doozy of a sentence... 
> 
> ... determines the address of a folio's index within a VMA when
>   - the folio belongs to a MAP_PRIVATE file-backed VMA, but
>   - <The VMA> has been cow'd
>   - thus <The CoW'd VMA> is anonymous (as well)
>   - The original VMA may or may not also be marked anonymous?
>     (just clarifying, could be original mapper or a COW that COWs)
> 
> Ow, my brain.  One question below
> 

After re-reading the cover-letter again - my note here is wrong and
my brain hurts more.

... determines the address of a folio's index within a VMA when
  - the folio belongs to a MAP_PRIVATE file-backed VMA, but
  - <The Folio> has been CoW'd
  - thus <The CoW'd Folio> is <now marked> anonymous
  - The original folio may or may not have been anonymous
    (depending on whether it, itself, was a CoW copy)

Lorenzo you are truly doing Darwin's work untangling all of this.

~Gregory