1 files changed, 215 insertions, 11 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index aa4b80dbe3ad..8f326ce2b690 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -483,7 +483,7 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc)
 			if (!sc->may_swap)
 				goto keep_locked;
 
-			switch (try_to_unmap(page)) {
+			switch (try_to_unmap(page, 0)) {
 			case SWAP_FAIL:
 				goto activate_locked;
 			case SWAP_AGAIN:
@@ -623,7 +623,7 @@ static int swap_page(struct page *page)
 	struct address_space *mapping = page_mapping(page);
 
 	if (page_mapped(page) && mapping)
-		if (try_to_unmap(page) != SWAP_SUCCESS)
+		if (try_to_unmap(page, 0) != SWAP_SUCCESS)
 			goto unlock_retry;
 
 	if (PageDirty(page)) {
@@ -659,6 +659,154 @@ unlock_retry:
 retry:
 	return -EAGAIN;
 }
+
+/*
+ * Page migration was first developed in the context of the memory hotplug
+ * project. The main authors of the migration code are:
+ *
+ * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
+ * Hirokazu Takahashi <taka@valinux.co.jp>
+ * Dave Hansen <haveblue@us.ibm.com>
+ * Christoph Lameter <clameter@sgi.com>
+ */
+
+/*
+ * Remove references for a page and establish the new page with the correct
+ * basic settings to be able to stop accesses to the page.
+ */
+static int migrate_page_remove_references(struct page *newpage,
+				struct page *page, int nr_refs)
+{
+	struct address_space *mapping = page_mapping(page);
+	struct page **radix_pointer;
+
+	/*
+	 * Avoid doing any of the following work if the page count
+	 * indicates that the page is in use or truncate has removed
+	 * the page.
+	 */
+	if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
+		return 1;
+
+	/*
+	 * Establish swap ptes for anonymous pages or destroy pte
+	 * maps for files.
+	 *
+	 * In order to reestablish file backed mappings the fault handlers
+	 * will take the radix tree_lock which may then be used to stop
+  	 * processses from accessing this page until the new page is ready.
+	 *
+	 * A process accessing via a swap pte (an anonymous page) will take a
+	 * page_lock on the old page which will block the process until the
+	 * migration attempt is complete. At that time the PageSwapCache bit
+	 * will be examined. If the page was migrated then the PageSwapCache
+	 * bit will be clear and the operation to retrieve the page will be
+	 * retried which will find the new page in the radix tree. Then a new
+	 * direct mapping may be generated based on the radix tree contents.
+	 *
+	 * If the page was not migrated then the PageSwapCache bit
+	 * is still set and the operation may continue.
+	 */
+	try_to_unmap(page, 1);
+
+	/*
+	 * Give up if we were unable to remove all mappings.
+	 */
+	if (page_mapcount(page))
+		return 1;
+
+	write_lock_irq(&mapping->tree_lock);
+
+	radix_pointer = (struct page **)radix_tree_lookup_slot(
+						&mapping->page_tree,
+						page_index(page));
+
+	if (!page_mapping(page) || page_count(page) != nr_refs ||
+			*radix_pointer != page) {
+		write_unlock_irq(&mapping->tree_lock);
+		return 1;
+	}
+
+	/*
+	 * Now we know that no one else is looking at the page.
+	 *
+	 * Certain minimal information about a page must be available
+	 * in order for other subsystems to properly handle the page if they
+	 * find it through the radix tree update before we are finished
+	 * copying the page.
+	 */
+	get_page(newpage);
+	newpage->index = page->index;
+	newpage->mapping = page->mapping;
+	if (PageSwapCache(page)) {
+		SetPageSwapCache(newpage);
+		set_page_private(newpage, page_private(page));
+	}
+
+	*radix_pointer = newpage;
+	__put_page(page);
+	write_unlock_irq(&mapping->tree_lock);
+
+	return 0;
+}
+
+/*
+ * Copy the page to its new location
+ */
+void migrate_page_copy(struct page *newpage, struct page *page)
+{
+	copy_highpage(newpage, page);
+
+	if (PageError(page))
+		SetPageError(newpage);
+	if (PageReferenced(page))
+		SetPageReferenced(newpage);
+	if (PageUptodate(page))
+		SetPageUptodate(newpage);
+	if (PageActive(page))
+		SetPageActive(newpage);
+	if (PageChecked(page))
+		SetPageChecked(newpage);
+	if (PageMappedToDisk(page))
+		SetPageMappedToDisk(newpage);
+
+	if (PageDirty(page)) {
+		clear_page_dirty_for_io(page);
+		set_page_dirty(newpage);
+ 	}
+
+	ClearPageSwapCache(page);
+	ClearPageActive(page);
+	ClearPagePrivate(page);
+	set_page_private(page, 0);
+	page->mapping = NULL;
+
+	/*
+	 * If any waiters have accumulated on the new page then
+	 * wake them up.
+	 */
+	if (PageWriteback(newpage))
+		end_page_writeback(newpage);
+}
+
+/*
+ * Common logic to directly migrate a single page suitable for
+ * pages that do not use PagePrivate.
+ *
+ * Pages are locked upon entry and exit.
+ */
+int migrate_page(struct page *newpage, struct page *page)
+{
+	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
+
+	if (migrate_page_remove_references(newpage, page, 2))
+		return -EAGAIN;
+
+	migrate_page_copy(newpage, page);
+
+	return 0;
+}
+
 /*
  * migrate_pages
  *
@@ -672,11 +820,6 @@ retry:
  * are movable anymore because t has become empty
  * or no retryable pages exist anymore.
  *
- * SIMPLIFIED VERSION: This implementation of migrate_pages
- * is only swapping out pages and never touches the second
- * list. The direct migration patchset
- * extends this function to avoid the use of swap.
- *
  * Return: Number of pages not migrated when "to" ran empty.
  */
 int migrate_pages(struct list_head *from, struct list_head *to,
@@ -697,6 +840,9 @@ redo:
 	retry = 0;
 
 	list_for_each_entry_safe(page, page2, from, lru) {
+		struct page *newpage = NULL;
+		struct address_space *mapping;
+
 		cond_resched();
 
 		rc = 0;
@@ -704,6 +850,9 @@ redo:
 			/* page was freed from under us. So we are done. */
 			goto next;
 
+		if (to && list_empty(to))
+			break;
+
 		/*
 		 * Skip locked pages during the first two passes to give the
 		 * functions holding the lock time to release the page. Later we
@@ -740,12 +889,64 @@ redo:
 			}
 		}
 
+		if (!to) {
+			rc = swap_page(page);
+			goto next;
+		}
+
+		newpage = lru_to_page(to);
+		lock_page(newpage);
+
 		/*
-		 * Page is properly locked and writeback is complete.
+		 * Pages are properly locked and writeback is complete.
 		 * Try to migrate the page.
 		 */
-		rc = swap_page(page);
-		goto next;
+		mapping = page_mapping(page);
+		if (!mapping)
+			goto unlock_both;
+
+		/*
+		 * Trigger writeout if page is dirty
+		 */
+		if (PageDirty(page)) {
+			switch (pageout(page, mapping)) {
+			case PAGE_KEEP:
+			case PAGE_ACTIVATE:
+				goto unlock_both;
+
+			case PAGE_SUCCESS:
+				unlock_page(newpage);
+				goto next;
+
+			case PAGE_CLEAN:
+				; /* try to migrate the page below */
+			}
+                }
+		/*
+		 * If we have no buffer or can release the buffer
+		 * then do a simple migration.
+		 */
+		if (!page_has_buffers(page) ||
+		    try_to_release_page(page, GFP_KERNEL)) {
+			rc = migrate_page(newpage, page);
+			goto unlock_both;
+		}
+
+		/*
+		 * On early passes with mapped pages simply
+		 * retry. There may be a lock held for some
+		 * buffers that may go away. Later
+		 * swap them out.
+		 */
+		if (pass > 4) {
+			unlock_page(newpage);
+			newpage = NULL;
+			rc = swap_page(page);
+			goto next;
+		}
+
+unlock_both:
+		unlock_page(newpage);
 
 unlock_page:
 		unlock_page(page);
@@ -758,7 +959,10 @@ next:
 			list_move(&page->lru, failed);
 			nr_failed++;
 		} else {
-			/* Success */
+			if (newpage) {
+				/* Successful migration. Return page to LRU */
+				move_to_lru(newpage);
+			}
 			list_move(&page->lru, moved);
 		}
 	}