[PATCH] Simplify migrate_page_add

Simplify migrate_page_add after feedback from Hugh.  This also allows us to
drop one parameter from migrate_page_add.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 36 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 551cde40520b..a683a66599b1 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -185,8 +185,8 @@ static struct mempolicy *mpol_new(int mode, nodemask_t *nodes)
 }
 
 static void gather_stats(struct page *, void *);
-static void migrate_page_add(struct vm_area_struct *vma,
-        struct page *page, struct list_head *pagelist, unsigned long flags);
+static void migrate_page_add(struct page *page, struct list_head *pagelist,
+                                unsigned long flags);
 
 /* Scan through pages checking if pages follow certain conditions. */
 static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
@@ -228,7 +228,7 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                 if (flags & MPOL_MF_STATS)
                         gather_stats(page, private);
                 else if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
-                        migrate_page_add(vma, page, private, flags);
+                        migrate_page_add(page, private, flags);
                 else
                         break;
         } while (pte++, addr += PAGE_SIZE, addr != end);
@@ -531,42 +531,13 @@ long do_get_mempolicy(int *policy, nodemask_t *nmask,
  * page migration
  */
 
-/* Check if we are the only process mapping the page in question */
-static inline int single_mm_mapping(struct mm_struct *mm,
-                        struct address_space *mapping)
-{
-        struct vm_area_struct *vma;
-        struct prio_tree_iter iter;
-        int rc = 1;
-
-        spin_lock(&mapping->i_mmap_lock);
-        vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
-                if (mm != vma->vm_mm) {
-                        rc = 0;
-                        goto out;
-                }
-        list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
-                if (mm != vma->vm_mm) {
-                        rc = 0;
-                        goto out;
-                }
-out:
-        spin_unlock(&mapping->i_mmap_lock);
-        return rc;
-}
-
-/*
- * Add a page to be migrated to the pagelist
- */
-static void migrate_page_add(struct vm_area_struct *vma,
-        struct page *page, struct list_head *pagelist, unsigned long flags)
+static void migrate_page_add(struct page *page, struct list_head *pagelist,
+                                unsigned long flags)
 {
         /*
-         * Avoid migrating a page that is shared by others and not writable.
+         * Avoid migrating a page that is shared with others.
          */
-        if ((flags & MPOL_MF_MOVE_ALL) || !page->mapping || PageAnon(page) ||
-            mapping_writably_mapped(page->mapping) ||
-            single_mm_mapping(vma->vm_mm, page->mapping)) {
+        if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(page) == 1) {
                 if (isolate_lru_page(page))
                         list_add(&page->lru, pagelist);
         }