diff options
Diffstat (limited to 'include/linux/balloon_compaction.h')
| -rw-r--r-- | include/linux/balloon_compaction.h | 97 |
1 files changed, 24 insertions, 73 deletions
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index 089743ade734..38aa07d5b81c 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -27,10 +27,13 @@ * counter raised only while it is under our special handling; * * iii. after the lockless scan step have selected a potential balloon page for - * isolation, re-test the page->mapping flags and the page ref counter + * isolation, re-test the PageBalloon mark and the PagePrivate flag * under the proper page lock, to ensure isolating a valid balloon page * (not yet isolated, nor under release procedure) * + * iv. isolation or dequeueing procedure must clear PagePrivate flag under + * page lock together with removing page from balloon device page list. + * * The functions provided by this interface are placed to help on coping with * the aforementioned balloon page corner case, as well as to ensure the simple * set of exposed rules are satisfied while we are dealing with balloon pages @@ -71,28 +74,6 @@ static inline void balloon_devinfo_free(struct balloon_dev_info *b_dev_info) kfree(b_dev_info); } -/* - * balloon_page_free - release a balloon page back to the page free lists - * @page: ballooned page to be set free - * - * This function must be used to properly set free an isolated/dequeued balloon - * page at the end of a sucessful page migration, or at the balloon driver's - * page release procedure. - */ -static inline void balloon_page_free(struct page *page) -{ - /* - * Balloon pages always get an extra refcount before being isolated - * and before being dequeued to help on sorting out fortuite colisions - * between a thread attempting to isolate and another thread attempting - * to release the very same balloon page. - * - * Before we handle the page back to Buddy, lets drop its extra refcnt. - */ - put_page(page); - __free_page(page); -} - #ifdef CONFIG_BALLOON_COMPACTION extern bool balloon_page_isolate(struct page *page); extern void balloon_page_putback(struct page *page); @@ -108,74 +89,33 @@ static inline void balloon_mapping_free(struct address_space *balloon_mapping) } /* - * page_flags_cleared - helper to perform balloon @page ->flags tests. - * - * As balloon pages are obtained from buddy and we do not play with page->flags - * at driver level (exception made when we get the page lock for compaction), - * we can safely identify a ballooned page by checking if the - * PAGE_FLAGS_CHECK_AT_PREP page->flags are all cleared. This approach also - * helps us skip ballooned pages that are locked for compaction or release, thus - * mitigating their racy check at balloon_page_movable() - */ -static inline bool page_flags_cleared(struct page *page) -{ - return !(page->flags & PAGE_FLAGS_CHECK_AT_PREP); -} - -/* - * __is_movable_balloon_page - helper to perform @page mapping->flags tests + * __is_movable_balloon_page - helper to perform @page PageBalloon tests */ static inline bool __is_movable_balloon_page(struct page *page) { - struct address_space *mapping = page->mapping; - return mapping_balloon(mapping); + return PageBalloon(page); } /* - * balloon_page_movable - test page->mapping->flags to identify balloon pages - * that can be moved by compaction/migration. - * - * This function is used at core compaction's page isolation scheme, therefore - * most pages exposed to it are not enlisted as balloon pages and so, to avoid - * undesired side effects like racing against __free_pages(), we cannot afford - * holding the page locked while testing page->mapping->flags here. + * balloon_page_movable - test PageBalloon to identify balloon pages + * and PagePrivate to check that the page is not + * isolated and can be moved by compaction/migration. * * As we might return false positives in the case of a balloon page being just - * released under us, the page->mapping->flags need to be re-tested later, - * under the proper page lock, at the functions that will be coping with the - * balloon page case. + * released under us, this need to be re-tested later, under the page lock. */ static inline bool balloon_page_movable(struct page *page) { - /* - * Before dereferencing and testing mapping->flags, let's make sure - * this is not a page that uses ->mapping in a different way - */ - if (page_flags_cleared(page) && !page_mapped(page) && - page_count(page) == 1) - return __is_movable_balloon_page(page); - - return false; + return PageBalloon(page) && PagePrivate(page); } /* * isolated_balloon_page - identify an isolated balloon page on private * compaction/migration page lists. - * - * After a compaction thread isolates a balloon page for migration, it raises - * the page refcount to prevent concurrent compaction threads from re-isolating - * the same page. For that reason putback_movable_pages(), or other routines - * that need to identify isolated balloon pages on private pagelists, cannot - * rely on balloon_page_movable() to accomplish the task. */ static inline bool isolated_balloon_page(struct page *page) { - /* Already isolated balloon pages, by default, have a raised refcount */ - if (page_flags_cleared(page) && !page_mapped(page) && - page_count(page) >= 2) - return __is_movable_balloon_page(page); - - return false; + return PageBalloon(page); } /* @@ -192,6 +132,8 @@ static inline void balloon_page_insert(struct page *page, struct address_space *mapping, struct list_head *head) { + __SetPageBalloon(page); + SetPagePrivate(page); page->mapping = mapping; list_add(&page->lru, head); } @@ -206,8 +148,12 @@ static inline void balloon_page_insert(struct page *page, */ static inline void balloon_page_delete(struct page *page) { + __ClearPageBalloon(page); page->mapping = NULL; - list_del(&page->lru); + if (PagePrivate(page)) { + ClearPagePrivate(page); + list_del(&page->lru); + } } /* @@ -258,6 +204,11 @@ static inline void balloon_page_delete(struct page *page) list_del(&page->lru); } +static inline bool __is_movable_balloon_page(struct page *page) +{ + return false; +} + static inline bool balloon_page_movable(struct page *page) { return false; |