[PATCH] mm: rmap.c cleanup

mm/rmap.c:page_referenced_one() and mm/rmap.c:try_to_unmap_one() contain
identical code that

 - takes mm->page_table_lock;

 - drills through page tables;

 - checks that correct pte is reached.

Coalesce this into page_check_address()

Signed-off-by: Nikita Danilov <nikita@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/rmap.c b/mm/rmap.c
index 884d6d1..378de23 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -243,6 +243,42 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 }
 
 /*
+ * Check that @page is mapped at @address into @mm.
+ *
+ * On success returns with mapped pte and locked mm->page_table_lock.
+ */
+static pte_t *page_check_address(struct page *page, struct mm_struct *mm,
+                                       unsigned long address)
+{
+       pgd_t *pgd;
+       pud_t *pud;
+       pmd_t *pmd;
+       pte_t *pte;
+
+       /*
+        * We need the page_table_lock to protect us from page faults,
+        * munmap, fork, etc...
+        */
+       spin_lock(&mm->page_table_lock);
+       pgd = pgd_offset(mm, address);
+       if (likely(pgd_present(*pgd))) {
+               pud = pud_offset(pgd, address);
+               if (likely(pud_present(*pud))) {
+                       pmd = pmd_offset(pud, address);
+                       if (likely(pmd_present(*pmd))) {
+                               pte = pte_offset_map(pmd, address);
+                               if (likely(pte_present(*pte) &&
+                                          page_to_pfn(page) == pte_pfn(*pte)))
+                                       return pte;
+                               pte_unmap(pte);
+                       }
+               }
+       }
+       spin_unlock(&mm->page_table_lock);
+       return ERR_PTR(-ENOENT);
+}
+
+/*
  * Subfunctions of page_referenced: page_referenced_one called
  * repeatedly from either page_referenced_anon or page_referenced_file.
  */
@@ -251,9 +287,6 @@ static int page_referenced_one(struct page *page,
 {
        struct mm_struct *mm = vma->vm_mm;
        unsigned long address;
-       pgd_t *pgd;
-       pud_t *pud;
-       pmd_t *pmd;
        pte_t *pte;
        int referenced = 0;
 
@@ -263,39 +296,18 @@ static int page_referenced_one(struct page *page,
        if (address == -EFAULT)
                goto out;
 
-       spin_lock(&mm->page_table_lock);
-
-       pgd = pgd_offset(mm, address);
-       if (!pgd_present(*pgd))
-               goto out_unlock;
-
-       pud = pud_offset(pgd, address);
-       if (!pud_present(*pud))
-               goto out_unlock;
-
-       pmd = pmd_offset(pud, address);
-       if (!pmd_present(*pmd))
-               goto out_unlock;
-
-       pte = pte_offset_map(pmd, address);
-       if (!pte_present(*pte))
-               goto out_unmap;
-
-       if (page_to_pfn(page) != pte_pfn(*pte))
-               goto out_unmap;
-
-       if (ptep_clear_flush_young(vma, address, pte))
-               referenced++;
-
-       if (mm != current->mm && !ignore_token && has_swap_token(mm))
-               referenced++;
+       pte = page_check_address(page, mm, address);
+       if (!IS_ERR(pte)) {
+               if (ptep_clear_flush_young(vma, address, pte))
+                       referenced++;
 
-       (*mapcount)--;
+               if (mm != current->mm && !ignore_token && has_swap_token(mm))
+                       referenced++;
 
-out_unmap:
-       pte_unmap(pte);
-out_unlock:
-       spin_unlock(&mm->page_table_lock);
+               (*mapcount)--;
+               pte_unmap(pte);
+               spin_unlock(&mm->page_table_lock);
+       }
 out:
        return referenced;
 }
@@ -502,9 +514,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
 {
        struct mm_struct *mm = vma->vm_mm;
        unsigned long address;
-       pgd_t *pgd;
-       pud_t *pud;
-       pmd_t *pmd;
        pte_t *pte;
        pte_t pteval;
        int ret = SWAP_AGAIN;
@@ -515,30 +524,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
        if (address == -EFAULT)
                goto out;
 
-       /*
-        * We need the page_table_lock to protect us from page faults,
-        * munmap, fork, etc...
-        */
-       spin_lock(&mm->page_table_lock);
-
-       pgd = pgd_offset(mm, address);
-       if (!pgd_present(*pgd))
-               goto out_unlock;
-
-       pud = pud_offset(pgd, address);
-       if (!pud_present(*pud))
-               goto out_unlock;
-
-       pmd = pmd_offset(pud, address);
-       if (!pmd_present(*pmd))
-               goto out_unlock;
-
-       pte = pte_offset_map(pmd, address);
-       if (!pte_present(*pte))
-               goto out_unmap;
-
-       if (page_to_pfn(page) != pte_pfn(*pte))
-               goto out_unmap;
+       pte = page_check_address(page, mm, address);
+       if (IS_ERR(pte))
+               goto out;
 
        /*
         * If the page is mlock()d, we cannot swap it out.
@@ -604,7 +592,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
 
 out_unmap:
        pte_unmap(pte);
-out_unlock:
        spin_unlock(&mm->page_table_lock);
 out:
        return ret;
@@ -708,7 +695,6 @@ static void try_to_unmap_cluster(unsigned long cursor,
        }
 
        pte_unmap(pte);
-
 out_unlock:
        spin_unlock(&mm->page_table_lock);
 }
@@ -860,3 +846,4 @@ int try_to_unmap(struct page *page)
                ret = SWAP_SUCCESS;
        return ret;
 }
+