memory unplug: migration by kernel

[safe/jmp/linux-2.6] / mm / migrate.c

diff --git a/mm/migrate.c b/mm/migrate.c
index 7a66ca2..c8d8722 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -297,7 +297,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
        void **pslot;
 
        if (!mapping) {
-               /* Anonymous page */
+               /* Anonymous page without mapping */
                if (page_count(page) != 1)
                        return -EAGAIN;
                return 0;
@@ -333,6 +333,19 @@ static int migrate_page_move_mapping(struct address_space *mapping,
         */
        __put_page(page);
 
+       /*
+        * If moved to a different zone then also account
+        * the page for that zone. Other VM counters will be
+        * taken care of when we establish references to the
+        * new page and drop references to the old page.
+        *
+        * Note that anonymous pages are accounted for
+        * via NR_FILE_PAGES and NR_ANON_PAGES if they
+        * are mapped to swap space.
+        */
+       __dec_zone_page_state(page, NR_FILE_PAGES);
+       __inc_zone_page_state(newpage, NR_FILE_PAGES);
+
        write_unlock_irq(&mapping->tree_lock);
 
        return 0;
@@ -619,18 +632,35 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
                        goto unlock;
                wait_on_page_writeback(page);
        }
-
        /*
-        * Establish migration ptes or remove ptes
+        * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
+        * we cannot notice that anon_vma is freed while we migrates a page.
+        * This rcu_read_lock() delays freeing anon_vma pointer until the end
+        * of migration. File cache pages are no problem because of page_lock()
         */
+       rcu_read_lock();
+       /*
+        * This is a corner case handling.
+        * When a new swap-cache is read into, it is linked to LRU
+        * and treated as swapcache but has no rmap yet.
+        * Calling try_to_unmap() against a page->mapping==NULL page is
+        * BUG. So handle it here.
+        */
+       if (!page->mapping)
+               goto rcu_unlock;
+       /* Establish migration ptes or remove ptes */
        try_to_unmap(page, 1);
+
        if (!page_mapped(page))
                rc = move_to_new_page(newpage, page);
 
        if (rc)
                remove_migration_ptes(page, page);
+rcu_unlock:
+       rcu_read_unlock();
 
 unlock:
+
        unlock_page(page);
 
        if (rc != -EAGAIN) {
@@ -748,7 +778,8 @@ static struct page *new_page_node(struct page *p, unsigned long private,
 
        *result = &pm->status;
 
-       return alloc_pages_node(pm->node, GFP_HIGHUSER | GFP_THISNODE, 0);
+       return alloc_pages_node(pm->node,
+                               GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
 }
 
 /*