From 6c5240ae7f48c83fcaa8e24fa63e7eb09aba5651 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Fri, 23 Jun 2006 02:03:37 -0700 Subject: [PATCH] [PATCH] Swapless page migration: modify core logic Use the migration entries for page migration This modifies the migration code to use the new migration entries. It now becomes possible to migrate anonymous pages without having to add a swap entry. We add a couple of new functions to replace migration entries with the proper ptes. We cannot take the tree_lock for migrating anonymous pages anymore. However, we know that we hold the only remaining reference to the page when the page count reaches 1. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 4 ++-- mm/migrate.c | 53 +++++++++++++++++++++------------------------------- 2 files changed, 23 insertions(+), 34 deletions(-) diff --git a/mm/Kconfig b/mm/Kconfig index 332f5c29b5..66e65ab394 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -138,8 +138,8 @@ config SPLIT_PTLOCK_CPUS # config MIGRATION bool "Page migration" - def_bool y if NUMA - depends on SWAP && NUMA + def_bool y + depends on NUMA help Allows the migration of the physical location of pages of processes while the virtual addresses are not changed. This is useful for diff --git a/mm/migrate.c b/mm/migrate.c index 81721a061d..8f91463eab 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -254,14 +254,20 @@ static int migrate_page_move_mapping(struct address_space *mapping, { struct page **radix_pointer; + if (!mapping) { + /* Anonymous page */ + if (page_count(page) != 1) + return -EAGAIN; + return 0; + } + 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) != 2 + !!PagePrivate(page) || + if (page_count(page) != 2 + !!PagePrivate(page) || *radix_pointer != page) { write_unlock_irq(&mapping->tree_lock); return -EAGAIN; @@ -271,10 +277,12 @@ static int migrate_page_move_mapping(struct address_space *mapping, * Now we know that no one else is looking at the page. */ get_page(newpage); +#ifdef CONFIG_SWAP if (PageSwapCache(page)) { SetPageSwapCache(newpage); set_page_private(newpage, page_private(page)); } +#endif *radix_pointer = newpage; __put_page(page); @@ -308,7 +316,9 @@ static void migrate_page_copy(struct page *newpage, struct page *page) set_page_dirty(newpage); } +#ifdef CONFIG_SWAP ClearPageSwapCache(page); +#endif ClearPageActive(page); ClearPagePrivate(page); set_page_private(page, 0); @@ -353,16 +363,6 @@ int migrate_page(struct address_space *mapping, return rc; migrate_page_copy(newpage, page); - - /* - * Remove auxiliary swap entries and replace - * them with real ptes. - * - * Note that a real pte entry will allow processes that are not - * waiting on the page lock to use the new page via the page tables - * before the new page is unlocked. - */ - remove_from_swap(newpage); return 0; } EXPORT_SYMBOL(migrate_page); @@ -530,23 +530,7 @@ redo: goto unlock_page; /* - * 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. + * Establish migration ptes or remove ptes */ rc = -EPERM; if (try_to_unmap(page, 1) == SWAP_FAIL) @@ -569,9 +553,9 @@ redo: */ mapping = page_mapping(page); if (!mapping) - goto unlock_both; + rc = migrate_page(mapping, newpage, page); - if (mapping->a_ops->migratepage) + else if (mapping->a_ops->migratepage) /* * Most pages have a mapping and most filesystems * should provide a migration function. Anonymous @@ -584,10 +568,15 @@ redo: else rc = fallback_migrate_page(mapping, newpage, page); -unlock_both: + if (!rc) + remove_migration_ptes(page, newpage); + unlock_page(newpage); unlock_page: + if (rc) + remove_migration_ptes(page, page); + unlock_page(page); next: -- 2.39.5