Re: [PATCH v2 00/15] mm/rmap: index MAP_PRIVATE file-backed folios by virt pgoff

[Lorenzo Stoakes (ARM)]

On Mon, Jul 20, 2026 at 12:48:12PM -0700, Andrew Morton wrote:
> On Mon, 20 Jul 2026 15:38:26 +0100 "Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:
>
> > In memory management we've managed to manufacture a great deal of confusion
> > around the concept of anonymous memory. We have:
> >
> > 1. 'Pure anon' memory - anonymous VMAs whose folios are anonymous and
> >    swap-backed (thus for reclaim purposes, treated as anonymous). These are
> >    simple enough.
> >
> > 2. shmem - file-backed VMAs, file-backed folios (from rmap perspective) so
> >    present in the page cache and mapped by an address_space object, but
> >    whose folios are also swap-backed (thus treated as anonymous for reclaim
> >    purposes).
> >
> > 3. MAP_PRIVATE-mapped /dev/zero - a strange beast whose VMAs have
> >    vma->vm_file set, but whose mmap_prepare callback clears vma->vm_ops to
> >    satisfy vma_is_anonymous(), which results in VMAs that were mmap()'d
> >    referencing a file, but are in every other sense anonymous, including the
> >    folios.
> >
> > 4. Other MAP_PRIVATE-file backed mappings - These possess file-backed VMAs
> >    and have file-backed folios until CoW'd, at which point those CoW'd
> >    folios are anonymous.
> >
> > This series fixes issues 3 and 4.
>
> Thanks, I'll add this to mm-new for review-n-test.
>
> AI review seems overloaded at present, might have found a few things:
> 	https://sashiko.dev/#/patchset/20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@xxxxxxxxxx
>

Thanks, will have a look through the sashiko stuff and see what's valid.

Cheers, Lorenzo