Re: [PATCH 1/2] mm: always call rmap_walk() on locked folios

[Peter Xu <peterx@redhat.com>]

On Mon, Oct 06, 2025 at 10:02:45PM +0200, David Hildenbrand wrote:
> Just like other anonymous folios we can walk the rmap to unmap/migrate them.
> And just like anonymous folios, they are not added to a page cache.
> 
> COW-sharing etc. works the very same way for them.

I agree. After all, many of the folio fields are reused here.

> 
> So I think they are really just anonymous folios representing a chunk of
> device memory that is not addressable by the CPU. Apart from that, nothing
> should be too special about them (well, except the way they are mapped into
> page tables of course).

I think they're still very special, though.. not only because they're
essentially swap entries, but also because I don't strictly think they're
really "anonymous", per the definition of normal anon private folios..

After all, they are closely attached to whatever device driver is providing
the service under the hood.  It doesn't really have a page cache, but it
kind of having it maintained in the device model..

The "private" side is accurate and uncontroversial.

Thanks,

-- 
Peter Xu