2/4 Migration Cache - add mm checks

Index: linux-2.6.16-rc3-mm1/mm/memory.c
===================================================================
@@ -1825,6 +1825,14 @@ void swapin_readahead(swp_entry_t entry,
 	unsigned long offset;
 
 	/*
+	 * no-op for migration cache entries.
+	 * do_swap_page() or shmem_getpage() might hand us one of these.
+TODO:   should be BUG_ON()?
+	 */
+	if (migration_type(swp_type(entry)))
+		return;
+
+	/*
 	 * Get the number of handles we should do readahead io to.
 	 */
 	num = valid_swaphandles(entry, &offset);

Index: linux-2.6.16-rc3-mm1/mm/swap_state.c
===================================================================
@@ -393,6 +393,7 @@ int add_to_swap(struct page * page, gfp_
 
 	if (!PageLocked(page))
 		BUG();
+	BUG_ON(page_is_migration(page));
 
 	for (;;) {
 		entry = get_swap_page();

@@ -543,6 +544,11 @@ struct page * lookup_swap_cache(swp_entr
 {
 	struct page *page;
 
+	if (migration_type(swp_type(entry))) {
+		page = lookup_migration_cache(entry);
+		return page;
+	}
+
 	page = find_get_page(&swapper_space, entry.val);
 
 	if (page)

@@ -564,6 +570,14 @@ struct page *read_swap_cache_async(swp_e
 	struct page *found_page, *new_page = NULL;
 	int err;
 
+	/*
+	 * return NULL for migration cache entries.
+	 * do_swap_page() or shmem_swapin() might hand us one of these.
+TODO:  should be BUG_ON() ?
+	 */
+	if (migration_type(swp_type(entry)))
+		return NULL;
+
 	do {
 		/*
 		 * First check the swap cache.  Since this is normally

83 lines not on this page · raw message

Index: linux-2.6.16-rc3-mm1/include/linux/mm.h
===================================================================
@@ -547,6 +547,14 @@ void page_address_init(void);
 #define page_address_init()  do { } while(0)
 #endif
 
+#ifdef CONFIG_MIGRATION
+//TODO:  can I make this 'static inline' here?  header dependencies?
+extern int page_is_migration(struct page *);
+extern struct address_space migration_space;
+#else
+#define page_is_migration(p) (0)
+#endif
+
 /*
  * On an anonymous page mapped into a user virtual memory area,
  * page->mapping points to its anon_vma, not to a struct address_space;

@@ -563,9 +571,12 @@ static inline struct address_space *page
 {
 	struct address_space *mapping = page->mapping;
 
-	if (unlikely(PageSwapCache(page)))
-		mapping = &swapper_space;
-	else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
+	if (unlikely(PageSwapCache(page))) {
+		if (unlikely(page_is_migration(page)))
+			mapping = &migration_space;
+		else
+			mapping = &swapper_space;
+	} else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
 		mapping = NULL;
 	return mapping;
 }

Index: linux-2.6.16-rc3-mm1/mm/vmscan.c
===================================================================
@@ -457,11 +457,19 @@ static unsigned long shrink_page_list(st
 		 * Anonymous process memory has backing store?
 		 * Try to allocate it some swap space here.
 		 */
-		if (PageAnon(page) && !PageSwapCache(page)) {
-			if (!sc->may_swap)
+		if (PageAnon(page)) {
+			if (!PageSwapCache(page)) {
+				if (!sc->may_swap)
+					goto keep_locked;
+				if (!add_to_swap(page, GFP_ATOMIC))
+					goto activate_locked;
+			} else if (page_is_migration(page)) {
+				/*
+				 * For now, skip migration cache pages.
+				 * TODO:  move to swap cache [difficult?]
+				 */
 				goto keep_locked;
-			if (!add_to_swap(page, GFP_ATOMIC))
-				goto activate_locked;
+			}
 		}
 #endif /* CONFIG_SWAP */
 

Index: linux-2.6.16-rc3-mm1/mm/rmap.c
===================================================================
@@ -232,7 +232,13 @@ void remove_from_swap(struct page *page)
 
 	spin_unlock(&anon_vma->lock);
 
-	delete_from_swap_cache(page);
+	if (PageSwapCache(page))
+		delete_from_swap_cache(page);
+	/*
+	 * if page was in migration cache, it will have been
+	 * removed when the last swap pte referencing the entry
+	 * was removed by the loop above.
+	 */
 }
 EXPORT_SYMBOL(remove_from_swap);
 #endif