Re: [PATCH 3/3] mm: remove page_mapped()

[Matthew Wilcox]

On Mon, Apr 27, 2026 at 01:43:16PM +0200, David Hildenbrand (Arm) wrote:
> Let's replace the last user of page_mapped() by folio_mapped() so we
> can get rid of page_mapped().

Yay!

> Replace the remaining occurrences of page_mapped() in rmap documentation
> by folio_mapped().

Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>

> +++ b/mm/memory.c
> @@ -5464,7 +5464,7 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
>  	if (unlikely(PageHWPoison(vmf->page))) {
>  		vm_fault_t poisonret = VM_FAULT_HWPOISON;
>  		if (ret & VM_FAULT_LOCKED) {
> -			if (page_mapped(vmf->page))
> +			if (folio_mapped(folio))
>  				unmap_mapping_folio(folio);

The idiot who authored 01d1e0e6b7d9 really should have done this at the
time ... Oh, wait, I see what I was trying to do.

I believe my thinking was that we only needed to unmap the folio if
this specific page that had hardware poison was mapped.  But no, we need
to unmap the entire folio if any page in it is mapped.

Does the affect recoverability from hwpoison?  I don't think so.  When
we detect hwpoison, the first thing we try to do is split the folio.
Of course that can fail, but if we do, we kill the process.

So yes, my R-b above stands.