Re: [RFC 19/19] mm, netmem: remove the page pool members in struct page

[Matthew Wilcox <willy@infradead.org>]

On Tue, May 13, 2025 at 10:42:00AM +0900, Byungchul Park wrote:
> Just in case, lemme explain what I meant, for *example*:

I understood what you meant.

> In here, operating on struct netmem_desc can smash _mapcount and
> _refcount in struct page unexpectedly, even though sizeof(struct
> netmem_desc) <= sizeof(struct page).  That's why I think the place holder
> is necessary until it completely gets separated so as to have its own
> instance.

We could tighten up the assert a bit.  eg

static_assert(sizeof(struct netmem_desc) <= offsetof(struct page, _refcount));

We _can't_ shrink struct page until struct folio is dynamically
allocated.  The same patch series that dynamically allocates folio will
do the same for netmem and slab and ptdesc and ...