[PATCH v2 3/5] mm/memory: pass folio and pte to restore_exclusive_pte()

[David Hildenbrand <david@redhat.com>]

Let's pass the folio and the pte to restore_exclusive_pte(), so we
can avoid repeated page_folio() and ptep_get(). To do that,
pass the pte to try_restore_exclusive_pte() and use a folio in there
already.

While at it, just avoid the "swp_entry_t entry" variable in
try_restore_exclusive_pte() and add a folio-locked check to
restore_exclusive_pte().

Reviewed-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/memory.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 507045fa719cc..2a0b4dd858769 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -719,14 +719,13 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
 #endif
 
 static void restore_exclusive_pte(struct vm_area_struct *vma,
-				  struct page *page, unsigned long address,
-				  pte_t *ptep)
+		struct folio *folio, struct page *page, unsigned long address,
+		pte_t *ptep, pte_t orig_pte)
 {
-	struct folio *folio = page_folio(page);
-	pte_t orig_pte;
 	pte_t pte;
 
-	orig_pte = ptep_get(ptep);
+	VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
+
 	pte = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
 	if (pte_swp_soft_dirty(orig_pte))
 		pte = pte_mksoft_dirty(pte);
@@ -753,16 +752,15 @@ static void restore_exclusive_pte(struct vm_area_struct *vma,
  * Tries to restore an exclusive pte if the page lock can be acquired without
  * sleeping.
  */
-static int
-try_restore_exclusive_pte(pte_t *src_pte, struct vm_area_struct *vma,
-			unsigned long addr)
+static int try_restore_exclusive_pte(struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep, pte_t orig_pte)
 {
-	swp_entry_t entry = pte_to_swp_entry(ptep_get(src_pte));
-	struct page *page = pfn_swap_entry_to_page(entry);
+	struct page *page = pfn_swap_entry_to_page(pte_to_swp_entry(orig_pte));
+	struct folio *folio = page_folio(page);
 
-	if (trylock_page(page)) {
-		restore_exclusive_pte(vma, page, addr, src_pte);
-		unlock_page(page);
+	if (folio_trylock(folio)) {
+		restore_exclusive_pte(vma, folio, page, addr, ptep, orig_pte);
+		folio_unlock(folio);
 		return 0;
 	}
 
@@ -868,7 +866,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		 * (ie. COW) mappings.
 		 */
 		VM_BUG_ON(!is_cow_mapping(src_vma->vm_flags));
-		if (try_restore_exclusive_pte(src_pte, src_vma, addr))
+		if (try_restore_exclusive_pte(src_vma, addr, src_pte, orig_pte))
 			return -EBUSY;
 		return -ENOENT;
 	} else if (is_pte_marker_entry(entry)) {
@@ -4030,7 +4028,8 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
 	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
 				&vmf->ptl);
 	if (likely(vmf->pte && pte_same(ptep_get(vmf->pte), vmf->orig_pte)))
-		restore_exclusive_pte(vma, vmf->page, vmf->address, vmf->pte);
+		restore_exclusive_pte(vma, folio, vmf->page, vmf->address,
+				      vmf->pte, vmf->orig_pte);
 
 	if (vmf->pte)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
-- 
2.48.1