[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>

1 files changed, 50 insertions, 63 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 884d6d1928bc..378de234c12b 100644
--- 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;
 }
+