On 10.01.25 07:00, Alistair Popple wrote:
In preparation for using insert_page() for DAX, enhance
insert_page_into_pte_locked() to handle establishing writable
mappings. Recall that DAX returns VM_FAULT_NOPAGE after installing a
PTE which bypasses the typical set_pte_range() in finish_fault.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Changes for v5:
- Minor comment/formatting fixes suggested by David Hildenbrand
Changes since v2:
- New patch split out from "mm/memory: Add dax_insert_pfn"
---
mm/memory.c | 37 +++++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 06bb29e..8531acb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2126,19 +2126,40 @@ static int validate_page_before_insert(struct vm_area_struct *vma,
}
static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
- unsigned long addr, struct page *page, pgprot_t prot)
+ unsigned long addr, struct page *page,
+ pgprot_t prot, bool mkwrite)
{
struct folio *folio = page_folio(page);
+ pte_t entry = ptep_get(pte);
pte_t pteval;
>
Just drop "entry" and reuse "pteval"; even saves you from one bug below :)
pte_t pteval = ptep_get(pte);
- if (!pte_none(ptep_get(pte)))
- return -EBUSY;
+ if (!pte_none(entry)) {
+ if (!mkwrite)
+ return -EBUSY;
+
+ /* see insert_pfn(). */
+ if (pte_pfn(entry) != page_to_pfn(page)) {
+ WARN_ON_ONCE(!is_zero_pfn(pte_pfn(entry)));
+ return -EFAULT;
+ }
+ entry = maybe_mkwrite(entry, vma);
+ entry = pte_mkyoung(entry);
+ if (ptep_set_access_flags(vma, addr, pte, entry, 1))
+ update_mmu_cache(vma, addr, pte);
+ return 0;
+ }
+
/* Ok, finally just insert the thing.. */
pteval = mk_pte(page, prot);
if (unlikely(is_zero_folio(folio))) {
pteval = pte_mkspecial(pteval);
} else {
folio_get(folio);
+ entry = mk_pte(page, prot);
we already do "pteval = mk_pte(page, prot);" above?
And I think your change here does not do what you want, because you
modify the new "entry" but we do
set_pte_at(vma->vm_mm, addr, pte, pteval);
below ...
+ if (mkwrite) {
+ entry = pte_mkyoung(entry);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ }
So again, better just reuse pteval :)
--
Cheers,
David / dhildenb
