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);
                 /*