mm: add page_check_address_transhuge() helper

page_referenced_one() and page_idle_clear_pte_refs_one() duplicate the
code for looking up pte of a (possibly transhuge) page.  Move this code
to a new helper function, page_check_address_transhuge(), and make the
above mentioned functions use it.

This is just a cleanup, no functional changes are intended.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 54 deletions

diff --git a/mm/page_idle.c b/mm/page_idle.c
index 2c553ba969f8..4ea9c4ef5146 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -55,71 +55,26 @@ static int page_idle_clear_pte_refs_one(struct page *page,
 					unsigned long addr, void *arg)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	spinlock_t *ptl;
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
+	spinlock_t *ptl;
 	bool referenced = false;
 
-	pgd = pgd_offset(mm, addr);
-	if (!pgd_present(*pgd))
-		return SWAP_AGAIN;
-	pud = pud_offset(pgd, addr);
-	if (!pud_present(*pud))
+	if (!page_check_address_transhuge(page, mm, addr, &pmd, &pte, &ptl))
 		return SWAP_AGAIN;
-	pmd = pmd_offset(pud, addr);
-
-	if (pmd_trans_huge(*pmd)) {
-		ptl = pmd_lock(mm, pmd);
-		if (!pmd_present(*pmd))
-			goto unlock_pmd;
-		if (unlikely(!pmd_trans_huge(*pmd))) {
-			spin_unlock(ptl);
-			goto map_pte;
-		}
-
-		if (pmd_page(*pmd) != page)
-			goto unlock_pmd;
 
+	if (pte) {
+		referenced = ptep_clear_young_notify(vma, addr, pte);
+		pte_unmap(pte);
+	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 		referenced = pmdp_clear_young_notify(vma, addr, pmd);
-		spin_unlock(ptl);
-		goto found;
-unlock_pmd:
-		spin_unlock(ptl);
-		return SWAP_AGAIN;
 	} else {
-		pmd_t pmde = *pmd;
-
-		barrier();
-		if (!pmd_present(pmde) || pmd_trans_huge(pmde))
-			return SWAP_AGAIN;
-
-	}
-map_pte:
-	pte = pte_offset_map(pmd, addr);
-	if (!pte_present(*pte)) {
-		pte_unmap(pte);
-		return SWAP_AGAIN;
+		/* unexpected pmd-mapped page? */
+		WARN_ON_ONCE(1);
 	}
 
-	ptl = pte_lockptr(mm, pmd);
-	spin_lock(ptl);
-
-	if (!pte_present(*pte)) {
-		pte_unmap_unlock(pte, ptl);
-		return SWAP_AGAIN;
-	}
-
-	/* THP can be referenced by any subpage */
-	if (pte_pfn(*pte) - page_to_pfn(page) >= hpage_nr_pages(page)) {
-		pte_unmap_unlock(pte, ptl);
-		return SWAP_AGAIN;
-	}
+	spin_unlock(ptl);
 
-	referenced = ptep_clear_young_notify(vma, addr, pte);
-	pte_unmap_unlock(pte, ptl);
-found:
 	if (referenced) {
 		clear_page_idle(page);
 		/*