--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1398,10 +1398,7 @@ static int insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
}
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
- if (pfn_t_devmap(pfn))
- entry = pmd_mkdevmap(entry);
- else
- entry = pmd_mkspecial(entry);
+ entry = pmd_mkspecial(entry);
if (write) {
I just stumbled over this, and I think there is something off here in
the PMD/PUD case.
vmf_insert_folio_pmd() does a folio_get() + folio_add_file_rmap_pmd().
But then, we go ahead and turn this into a special mapping by setting it
pmd_mkdevmap()/pmd_mkspecial().
Consequently, vm_normal_page_pmd() would ignore them, not following the
rules documented for vm_normal_page() and behaving differently than
vmf_insert_page_mkwrite()->insert_page().
folio_add_file_rmap_pmd() should never set these things special/devmap
in the first place :/
What am I missing?
Note that fs/dax.c calls vmf_insert_folio_pmd() for PMDs and
vmf_insert_page_mkwrite() for PTEs.
Consequently, PTEs will never be marked special (corner case, shared
zeropage), but PMDs would always.
Hm?
--
Cheers,
David / dhildenb
