vm_normal_page() works on these mappings, so we'd also have to skip rmap
code when unmapping these pages etc. Maybe that's the whole reason we
have the rmap handling here: to not special-case the unmap path.
vm_insert_page() will set VM_MIXEDMAP and vm_normal_page() will skip
the page if CONFIG_ARCH_HAS_PTE_SPECIAL is enabled (it's enabled for
x86). So the unmap path will skip these kind of folios?
I think we run into the
if (likely(!pte_special(pte)))
goto check_pfn;
first and return these folios. That also matches the comment of
vm_normal_page: "VM_MIXEDMAP mappings can likewise contain memory with
or without ... _all_ pages with a struct page (that is, those where
pfn_valid is true) are refcounted and considered normal pages by the VM."
--
Cheers,
David / dhildenb
