diff options
| -rw-r--r-- | Documentation/vm/page_migration | 19 | ||||
| -rw-r--r-- | mm/migrate.c | 49 |
2 files changed, 30 insertions, 38 deletions
diff --git a/Documentation/vm/page_migration b/Documentation/vm/page_migration index 479c3d0329bd..fea5c0864170 100644 --- a/Documentation/vm/page_migration +++ b/Documentation/vm/page_migration @@ -92,27 +92,26 @@ Steps: 2. Insure that writeback is complete. -3. Prep the new page that we want to move to. It is locked - and set to not being uptodate so that all accesses to the new - page immediately lock while the move is in progress. +3. Lock the new page that we want to move to. It is locked so that accesses to + this (not yet uptodate) page immediately lock while the move is in progress. -4. The new page is prepped with some settings from the old page so that - accesses to the new page will discover a page with the correct settings. - -5. All the page table references to the page are converted to migration +4. All the page table references to the page are converted to migration entries. This decreases the mapcount of a page. If the resulting mapcount is not zero then we do not migrate the page. All user space processes that attempt to access the page will now wait on the page lock. -6. The radix tree lock is taken. This will cause all processes trying +5. The radix tree lock is taken. This will cause all processes trying to access the page via the mapping to block on the radix tree spinlock. -7. The refcount of the page is examined and we back out if references remain +6. The refcount of the page is examined and we back out if references remain otherwise we know that we are the only one referencing this page. -8. The radix tree is checked and if it does not contain the pointer to this +7. The radix tree is checked and if it does not contain the pointer to this page then we back out because someone else modified the radix tree. +8. The new page is prepped with some settings from the old page so that + accesses to the new page will discover a page with the correct settings. + 9. The radix tree is changed to point to the new page. 10. The reference count of the old page is dropped because the radix tree diff --git a/mm/migrate.c b/mm/migrate.c index 08a7b6c4c266..3067e40e7be9 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -320,6 +320,14 @@ int migrate_page_move_mapping(struct address_space *mapping, /* Anonymous page without mapping */ if (page_count(page) != expected_count) return -EAGAIN; + + /* No turning back from here */ + set_page_memcg(newpage, page_memcg(page)); + newpage->index = page->index; + newpage->mapping = page->mapping; + if (PageSwapBacked(page)) + SetPageSwapBacked(newpage); + return MIGRATEPAGE_SUCCESS; } @@ -355,8 +363,15 @@ int migrate_page_move_mapping(struct address_space *mapping, } /* - * Now we know that no one else is looking at the page. + * Now we know that no one else is looking at the page: + * no turning back from here. */ + set_page_memcg(newpage, page_memcg(page)); + newpage->index = page->index; + newpage->mapping = page->mapping; + if (PageSwapBacked(page)) + SetPageSwapBacked(newpage); + get_page(newpage); /* add cache reference */ if (PageSwapCache(page)) { SetPageSwapCache(newpage); @@ -403,12 +418,6 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, int expected_count; void **pslot; - if (!mapping) { - if (page_count(page) != 1) - return -EAGAIN; - return MIGRATEPAGE_SUCCESS; - } - spin_lock_irq(&mapping->tree_lock); pslot = radix_tree_lookup_slot(&mapping->page_tree, @@ -426,6 +435,9 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, return -EAGAIN; } + set_page_memcg(newpage, page_memcg(page)); + newpage->index = page->index; + newpage->mapping = page->mapping; get_page(newpage); radix_tree_replace_slot(pslot, newpage); @@ -730,21 +742,6 @@ static int move_to_new_page(struct page *newpage, struct page *page, VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); - /* Prepare mapping for the new page.*/ - newpage->index = page->index; - newpage->mapping = page->mapping; - if (PageSwapBacked(page)) - SetPageSwapBacked(newpage); - - /* - * Indirectly called below, migrate_page_copy() copies PG_dirty and thus - * needs newpage's memcg set to transfer memcg dirty page accounting. - * So perform memcg migration in two steps: - * 1. set newpage->mem_cgroup (here) - * 2. clear page->mem_cgroup (below) - */ - set_page_memcg(newpage, page_memcg(page)); - mapping = page_mapping(page); if (!mapping) rc = migrate_page(mapping, newpage, page, mode); @@ -767,9 +764,6 @@ static int move_to_new_page(struct page *newpage, struct page *page, set_page_memcg(page, NULL); if (!PageAnon(page)) page->mapping = NULL; - } else { - set_page_memcg(newpage, NULL); - newpage->mapping = NULL; } return rc; } @@ -971,10 +965,9 @@ out: * it. Otherwise, putback_lru_page() will drop the reference grabbed * during isolation. */ - if (put_new_page) { - ClearPageSwapBacked(newpage); + if (put_new_page) put_new_page(newpage, private); - } else if (unlikely(__is_movable_balloon_page(newpage))) { + else if (unlikely(__is_movable_balloon_page(newpage))) { /* drop our reference, page already in the balloon */ put_page(newpage); } else |