mm/page_vma_mapped: pte_offset_map_nolock() not pte_lockptr()

[linux-2.6-microblaze.git] / mm / page_vma_mapped.c

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 947dc74..2af7342 100644 (file)
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -13,16 +13,28 @@ static inline bool not_found(struct page_vma_mapped_walk *pvmw)
        return false;
 }
 
-static bool map_pte(struct page_vma_mapped_walk *pvmw)
+static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
 {
        if (pvmw->flags & PVMW_SYNC) {
                /* Use the stricter lookup */
                pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd,
                                                pvmw->address, &pvmw->ptl);
-               return true;
+               *ptlp = pvmw->ptl;
+               return !!pvmw->pte;
        }
 
-       pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
+       /*
+        * It is important to return the ptl corresponding to pte,
+        * in case *pvmw->pmd changes underneath us; so we need to
+        * return it even when choosing not to lock, in case caller
+        * proceeds to loop over next ptes, and finds a match later.
+        * Though, in most cases, page lock already protects this.
+        */
+       pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
+                                         pvmw->address, ptlp);
+       if (!pvmw->pte)
+               return false;
+
        if (pvmw->flags & PVMW_MIGRATION) {
                if (!is_swap_pte(*pvmw->pte))
                        return false;
@@ -51,7 +63,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw)
        } else if (!pte_present(*pvmw->pte)) {
                return false;
        }
-       pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
+       pvmw->ptl = *ptlp;
        spin_lock(pvmw->ptl);
        return true;
 }
@@ -156,6 +168,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
        struct vm_area_struct *vma = pvmw->vma;
        struct mm_struct *mm = vma->vm_mm;
        unsigned long end;
+       spinlock_t *ptl;
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
@@ -257,8 +270,11 @@ restart:
                        step_forward(pvmw, PMD_SIZE);
                        continue;
                }
-               if (!map_pte(pvmw))
+               if (!map_pte(pvmw, &ptl)) {
+                       if (!pvmw->pte)
+                               goto restart;
                        goto next_pte;
+               }
 this_pte:
                if (check_pte(pvmw))
                        return true;
@@ -281,7 +297,7 @@ next_pte:
                } while (pte_none(*pvmw->pte));
 
                if (!pvmw->ptl) {
-                       pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+                       pvmw->ptl = ptl;
                        spin_lock(pvmw->ptl);
                }
                goto this_pte;