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-rw-r--r--mm/rmap.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 05977471..0383acf 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -224,10 +224,14 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
/*
* Check that @page is mapped at @address into @mm.
*
+ * If @sync is false, page_check_address may perform a racy check to avoid
+ * the page table lock when the pte is not present (helpful when reclaiming
+ * highly shared pages).
+ *
* On success returns with pte mapped and locked.
*/
pte_t *page_check_address(struct page *page, struct mm_struct *mm,
- unsigned long address, spinlock_t **ptlp)
+ unsigned long address, spinlock_t **ptlp, int sync)
{
pgd_t *pgd;
pud_t *pud;
@@ -249,7 +253,7 @@ pte_t *page_check_address(struct page *page, struct mm_struct *mm,
pte = pte_offset_map(pmd, address);
/* Make a quick check before getting the lock */
- if (!pte_present(*pte)) {
+ if (!sync && !pte_present(*pte)) {
pte_unmap(pte);
return NULL;
}
@@ -281,7 +285,7 @@ static int page_referenced_one(struct page *page,
if (address == -EFAULT)
goto out;
- pte = page_check_address(page, mm, address, &ptl);
+ pte = page_check_address(page, mm, address, &ptl, 0);
if (!pte)
goto out;
@@ -450,7 +454,7 @@ static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
if (address == -EFAULT)
goto out;
- pte = page_check_address(page, mm, address, &ptl);
+ pte = page_check_address(page, mm, address, &ptl, 1);
if (!pte)
goto out;
@@ -704,7 +708,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (address == -EFAULT)
goto out;
- pte = page_check_address(page, mm, address, &ptl);
+ pte = page_check_address(page, mm, address, &ptl, 0);
if (!pte)
goto out;
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