On 30.06.25 10:04, Harry Yoo wrote:

On Wed, Jun 18, 2025 at 07:39:50PM +0200, David Hildenbrand wrote:

quoted

... and start moving back to per-page things that will absolutely not be
folio things in the future. Add documentation and a comment that the
remaining folio stuff (lock, refcount) will have to be reworked as well.

While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle
it gracefully (relevant with further changes), and convert a
WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE().

Signed-off-by: David Hildenbrand <redacted>
---

Haha yeah, back to pages after folio conversion :P
But makes sense.

Reviewed-by: Harry Yoo <redacted>

Side question: In the future, maybe we will be unable to tell whether
a page is compound or not, without first inspecting page->memdesc?
(e.g., struct slab could have an order and a pointer to the head page...
just imagining).

Right, it's not really clear what we would do in the future, but for 
anything that allocates a memdesc, that is possible.

We wouldn't even need the "head" + "tail" bit indication.

For things without an allocated memdesc (e.g., PageOffline), maybe 
compound pages will simply not apply.

Likely, the concept of compound pages as we knew it will go away.

-- 
Cheers,

David / dhildenb