[PATCH] Direct Migration V9: remove_from_swap() to remove swap ptes

Add remove_from_swap

remove_from_swap() allows the restoration of the pte entries that existed
before page migration occurred for anonymous pages by walking the reverse
maps.  This reduces swap use and establishes regular pte's without the need
for page faults.

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

1 files changed, 29 insertions, 0 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 13fad5fcdf79..f4b91d7aa5cf 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -206,6 +206,35 @@ out:
         return anon_vma;
 }
 
+#ifdef CONFIG_MIGRATION
+/*
+ * Remove an anonymous page from swap replacing the swap pte's
+ * through real pte's pointing to valid pages and then releasing
+ * the page from the swap cache.
+ *
+ * Must hold page lock on page.
+ */
+void remove_from_swap(struct page *page)
+{
+        struct anon_vma *anon_vma;
+        struct vm_area_struct *vma;
+
+        if (!PageAnon(page) || !PageSwapCache(page))
+                return;
+
+        anon_vma = page_lock_anon_vma(page);
+        if (!anon_vma)
+                return;
+
+        list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
+                remove_vma_swap(vma, page);
+
+        spin_unlock(&anon_vma->lock);
+
+        delete_from_swap_cache(page);
+}
+#endif
+
 /*
  * At what user virtual address is page expected in vma?
  */