[RFC PATCH 03/26] hugetlb: add make_huge_pte_with_shift

[James Houghton <jthoughton@google.com>]

This allows us to make huge PTEs at shifts other than the hstate shift,
which will be necessary for high-granularity mappings.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 mm/hugetlb.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5df838d86f32..0eec34edf3b2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4686,23 +4686,30 @@ const struct vm_operations_struct hugetlb_vm_ops = {
 	.pagesize = hugetlb_vm_op_pagesize,
 };
 
+static pte_t make_huge_pte_with_shift(struct vm_area_struct *vma,
+				      struct page *page, int writable,
+				      int shift)
+{
+	bool huge = shift > PAGE_SHIFT;
+	pte_t entry = huge ? mk_huge_pte(page, vma->vm_page_prot)
+			   : mk_pte(page, vma->vm_page_prot);
+
+	if (writable)
+		entry = huge ? huge_pte_mkwrite(entry) : pte_mkwrite(entry);
+	else
+		entry = huge ? huge_pte_wrprotect(entry) : pte_wrprotect(entry);
+	pte_mkyoung(entry);
+	if (huge)
+		entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
+	return entry;
+}
+
 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
-				int writable)
+			   int writable)
 {
-	pte_t entry;
 	unsigned int shift = huge_page_shift(hstate_vma(vma));
 
-	if (writable) {
-		entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
-					 vma->vm_page_prot)));
-	} else {
-		entry = huge_pte_wrprotect(mk_huge_pte(page,
-					   vma->vm_page_prot));
-	}
-	entry = pte_mkyoung(entry);
-	entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
-
-	return entry;
+	return make_huge_pte_with_shift(vma, page, writable, shift);
 }
 
 static void set_huge_ptep_writable(struct vm_area_struct *vma,
-- 
2.37.0.rc0.161.g10f37bed90-goog