mm: prepare page_referenced() and page_idle to new THP refcounting
Both page_referenced() and page_idle_clear_pte_refs_one() assume that
THP can only be mapped with PMD, so there's no reason to look on PTEs
for PageTransHuge() pages. That's no true anymore: THP can be mapped
with PTEs too.
The patch removes PageTransHuge() test from the functions and opencode
page table check.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index 31d8866..6127c00 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -814,58 +814,105 @@
spinlock_t *ptl;
int referenced = 0;
struct page_referenced_arg *pra = arg;
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
- if (unlikely(PageTransHuge(page))) {
- pmd_t *pmd;
-
- /*
- * rmap might return false positives; we must filter
- * these out using page_check_address_pmd().
- */
- pmd = page_check_address_pmd(page, mm, address, &ptl);
- if (!pmd)
+ if (unlikely(PageHuge(page))) {
+ /* when pud is not present, pte will be NULL */
+ pte = huge_pte_offset(mm, address);
+ if (!pte)
return SWAP_AGAIN;
- if (vma->vm_flags & VM_LOCKED) {
+ ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
+ goto check_pte;
+ }
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ return SWAP_AGAIN;
+ pud = pud_offset(pgd, address);
+ if (!pud_present(*pud))
+ return SWAP_AGAIN;
+ pmd = pmd_offset(pud, address);
+
+ if (pmd_trans_huge(*pmd)) {
+ int ret = SWAP_AGAIN;
+
+ 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 (vma->vm_flags & VM_LOCKED) {
pra->vm_flags |= VM_LOCKED;
- return SWAP_FAIL; /* To break the loop */
+ ret = SWAP_FAIL; /* To break the loop */
+ goto unlock_pmd;
}
if (pmdp_clear_flush_young_notify(vma, address, pmd))
referenced++;
spin_unlock(ptl);
+ goto found;
+unlock_pmd:
+ spin_unlock(ptl);
+ return ret;
} else {
- pte_t *pte;
+ pmd_t pmde = *pmd;
- /*
- * rmap might return false positives; we must filter
- * these out using page_check_address().
- */
- pte = page_check_address(page, mm, address, &ptl, 0);
- if (!pte)
+ barrier();
+ if (!pmd_present(pmde) || pmd_trans_huge(pmde))
return SWAP_AGAIN;
-
- if (vma->vm_flags & VM_LOCKED) {
- pte_unmap_unlock(pte, ptl);
- pra->vm_flags |= VM_LOCKED;
- return SWAP_FAIL; /* To break the loop */
- }
-
- if (ptep_clear_flush_young_notify(vma, address, pte)) {
- /*
- * Don't treat a reference through a sequentially read
- * mapping as such. If the page has been used in
- * another mapping, we will catch it; if this other
- * mapping is already gone, the unmap path will have
- * set PG_referenced or activated the page.
- */
- if (likely(!(vma->vm_flags & VM_SEQ_READ)))
- referenced++;
- }
- pte_unmap_unlock(pte, ptl);
+ }
+map_pte:
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte)) {
+ pte_unmap(pte);
+ return SWAP_AGAIN;
}
+ ptl = pte_lockptr(mm, pmd);
+check_pte:
+ 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;
+ }
+
+ if (vma->vm_flags & VM_LOCKED) {
+ pte_unmap_unlock(pte, ptl);
+ pra->vm_flags |= VM_LOCKED;
+ return SWAP_FAIL; /* To break the loop */
+ }
+
+ if (ptep_clear_flush_young_notify(vma, address, pte)) {
+ /*
+ * Don't treat a reference through a sequentially read
+ * mapping as such. If the page has been used in
+ * another mapping, we will catch it; if this other
+ * mapping is already gone, the unmap path will have
+ * set PG_referenced or activated the page.
+ */
+ if (likely(!(vma->vm_flags & VM_SEQ_READ)))
+ referenced++;
+ }
+ pte_unmap_unlock(pte, ptl);
+
+found:
if (referenced)
clear_page_idle(page);
if (test_and_clear_page_young(page))
@@ -912,7 +959,7 @@
int ret;
int we_locked = 0;
struct page_referenced_arg pra = {
- .mapcount = page_mapcount(page),
+ .mapcount = total_mapcount(page),
.memcg = memcg,
};
struct rmap_walk_control rwc = {