mm/hugetlb: take page table lock in follow_huge_pmd()

[android-x86/kernel.git] / mm / hugetlb.c

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d96b8bf..5aca370 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3675,28 +3675,48 @@ follow_huge_addr(struct mm_struct *mm, unsigned long address,
 
 struct page * __weak
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
-               pmd_t *pmd, int write)
+               pmd_t *pmd, int flags)
 {
-       struct page *page;
-
-       if (!pmd_present(*pmd))
-               return NULL;
-       page = pte_page(*(pte_t *)pmd);
-       if (page)
-               page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
+       struct page *page = NULL;
+       spinlock_t *ptl;
+retry:
+       ptl = pmd_lockptr(mm, pmd);
+       spin_lock(ptl);
+       /*
+        * make sure that the address range covered by this pmd is not
+        * unmapped from other threads.
+        */
+       if (!pmd_huge(*pmd))
+               goto out;
+       if (pmd_present(*pmd)) {
+               page = pte_page(*(pte_t *)pmd) +
+                       ((address & ~PMD_MASK) >> PAGE_SHIFT);
+               if (flags & FOLL_GET)
+                       get_page(page);
+       } else {
+               if (is_hugetlb_entry_migration(huge_ptep_get((pte_t *)pmd))) {
+                       spin_unlock(ptl);
+                       __migration_entry_wait(mm, (pte_t *)pmd, ptl);
+                       goto retry;
+               }
+               /*
+                * hwpoisoned entry is treated as no_page_table in
+                * follow_page_mask().
+                */
+       }
+out:
+       spin_unlock(ptl);
        return page;
 }
 
 struct page * __weak
 follow_huge_pud(struct mm_struct *mm, unsigned long address,
-               pud_t *pud, int write)
+               pud_t *pud, int flags)
 {
-       struct page *page;
+       if (flags & FOLL_GET)
+               return NULL;
 
-       page = pte_page(*(pte_t *)pud);
-       if (page)
-               page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
-       return page;
+       return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
 }
 
 #ifdef CONFIG_MEMORY_FAILURE