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/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 7aec5ee..72cd942 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -48,11 +48,6 @@
#endif
};
-extern pmd_t *page_check_address_pmd(struct page *page,
- struct mm_struct *mm,
- unsigned long address,
- spinlock_t **ptl);
-
#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index aa8ae83..0ef5f21 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -433,21 +433,26 @@
atomic_set(&(page)->_mapcount, -1);
}
+int __page_mapcount(struct page *page);
+
static inline int page_mapcount(struct page *page)
{
- int ret;
VM_BUG_ON_PAGE(PageSlab(page), page);
- ret = atomic_read(&page->_mapcount) + 1;
- if (PageCompound(page)) {
- page = compound_head(page);
- ret += atomic_read(compound_mapcount_ptr(page)) + 1;
- if (PageDoubleMap(page))
- ret--;
- }
- return ret;
+ if (unlikely(PageCompound(page)))
+ return __page_mapcount(page);
+ return atomic_read(&page->_mapcount) + 1;
}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+int total_mapcount(struct page *page);
+#else
+static inline int total_mapcount(struct page *page)
+{
+ return page_mapcount(page);
+}
+#endif
+
static inline int page_count(struct page *page)
{
return atomic_read(&compound_head(page)->_count);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f283cb7..ab544b1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1649,46 +1649,6 @@
return false;
}
-/*
- * This function returns whether a given @page is mapped onto the @address
- * in the virtual space of @mm.
- *
- * When it's true, this function returns *pmd with holding the page table lock
- * and passing it back to the caller via @ptl.
- * If it's false, returns NULL without holding the page table lock.
- */
-pmd_t *page_check_address_pmd(struct page *page,
- struct mm_struct *mm,
- unsigned long address,
- spinlock_t **ptl)
-{
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
-
- if (address & ~HPAGE_PMD_MASK)
- return NULL;
-
- pgd = pgd_offset(mm, address);
- if (!pgd_present(*pgd))
- return NULL;
- pud = pud_offset(pgd, address);
- if (!pud_present(*pud))
- return NULL;
- pmd = pmd_offset(pud, address);
-
- *ptl = pmd_lock(mm, pmd);
- if (!pmd_present(*pmd))
- goto unlock;
- if (pmd_page(*pmd) != page)
- goto unlock;
- if (pmd_trans_huge(*pmd))
- return pmd;
-unlock:
- spin_unlock(*ptl);
- return NULL;
-}
-
#define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
int hugepage_madvise(struct vm_area_struct *vma,
@@ -3097,20 +3057,6 @@
}
}
-static int total_mapcount(struct page *page)
-{
- int i, ret;
-
- ret = compound_mapcount(page);
- for (i = 0; i < HPAGE_PMD_NR; i++)
- ret += atomic_read(&page[i]._mapcount) + 1;
-
- if (PageDoubleMap(page))
- ret -= HPAGE_PMD_NR;
-
- return ret;
-}
-
static int __split_huge_page_tail(struct page *head, int tail,
struct lruvec *lruvec, struct list_head *list)
{
@@ -3211,6 +3157,25 @@
}
}
+int total_mapcount(struct page *page)
+{
+ int i, ret;
+
+ VM_BUG_ON_PAGE(PageTail(page), page);
+
+ if (likely(!PageCompound(page)))
+ return atomic_read(&page->_mapcount) + 1;
+
+ ret = compound_mapcount(page);
+ if (PageHuge(page))
+ return ret;
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ ret += atomic_read(&page[i]._mapcount) + 1;
+ if (PageDoubleMap(page))
+ ret -= HPAGE_PMD_NR;
+ return ret;
+}
+
/*
* This function splits huge page into normal pages. @page can point to any
* subpage of huge page to split. Split doesn't change the position of @page.
diff --git a/mm/page_idle.c b/mm/page_idle.c
index 1c245d9..2c553ba 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -56,23 +56,70 @@
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
+ pgd_t *pgd;
+ pud_t *pud;
pmd_t *pmd;
pte_t *pte;
bool referenced = false;
- if (unlikely(PageTransHuge(page))) {
- pmd = page_check_address_pmd(page, mm, addr, &ptl);
- if (pmd) {
- referenced = pmdp_clear_young_notify(vma, addr, pmd);
+ pgd = pgd_offset(mm, addr);
+ if (!pgd_present(*pgd))
+ return SWAP_AGAIN;
+ pud = pud_offset(pgd, addr);
+ if (!pud_present(*pud))
+ 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;
+
+ referenced = pmdp_clear_young_notify(vma, addr, pmd);
+ spin_unlock(ptl);
+ goto found;
+unlock_pmd:
+ spin_unlock(ptl);
+ return SWAP_AGAIN;
} else {
- pte = page_check_address(page, mm, addr, &ptl, 0);
- if (pte) {
- referenced = ptep_clear_young_notify(vma, addr, pte);
- pte_unmap_unlock(pte, ptl);
- }
+ 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;
+ }
+
+ 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;
+ }
+
+ referenced = ptep_clear_young_notify(vma, addr, pte);
+ pte_unmap_unlock(pte, ptl);
+found:
if (referenced) {
clear_page_idle(page);
/*
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 = {
diff --git a/mm/util.c b/mm/util.c
index 8acb936..6d1f920 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -407,6 +407,20 @@
return mapping;
}
+/* Slow path of page_mapcount() for compound pages */
+int __page_mapcount(struct page *page)
+{
+ int ret;
+
+ ret = atomic_read(&page->_mapcount) + 1;
+ page = compound_head(page);
+ ret += atomic_read(compound_mapcount_ptr(page)) + 1;
+ if (PageDoubleMap(page))
+ ret--;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__page_mapcount);
+
int overcommit_ratio_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)