From: Zi Yan <ziy@xxxxxxxxxx> Whenever the buddy of a page is found from __find_buddy_pfn(), page_is_buddy() should be used to check its validity. Add a helper function find_buddy_page_pfn() to find the buddy page and do the check together. Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/linux-mm/CAHk-=wji_AmYygZMTsPMdJ7XksMt7kOur8oDfDdniBRMjm4VkQ@xxxxxxxxxxxxxx/ Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> --- mm/internal.h | 23 +---------------- mm/page_alloc.c | 63 ++++++++++++++++++++++++++++++++++++++------- mm/page_isolation.c | 8 ++---- 3 files changed, 56 insertions(+), 38 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 876e66237c89..f43565ed5ff6 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -211,28 +211,7 @@ struct alloc_context { bool spread_dirty_pages; }; -/* - * Locate the struct page for both the matching buddy in our - * pair (buddy1) and the combined O(n+1) page they form (page). - * - * 1) Any buddy B1 will have an order O twin B2 which satisfies - * the following equation: - * B2 = B1 ^ (1 << O) - * For example, if the starting buddy (buddy2) is #8 its order - * 1 buddy is #10: - * B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10 - * - * 2) Any buddy B will have an order O+1 parent P which - * satisfies the following equation: - * P = B & ~(1 << O) - * - * Assumption: *_mem_map is contiguous at least up to MAX_ORDER - */ -static inline unsigned long -__find_buddy_pfn(unsigned long page_pfn, unsigned int order) -{ - return page_pfn ^ (1 << order); -} +extern struct page *find_buddy_page_pfn(struct page *page, unsigned int order); extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn, unsigned long end_pfn, struct zone *zone); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2ea106146686..8aedc6fbfdd0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -998,6 +998,51 @@ static inline void del_page_from_free_list(struct page *page, struct zone *zone, zone->free_area[order].nr_free--; } +/* + * Locate the struct page for both the matching buddy in our + * pair (buddy1) and the combined O(n+1) page they form (page). + * + * 1) Any buddy B1 will have an order O twin B2 which satisfies + * the following equation: + * B2 = B1 ^ (1 << O) + * For example, if the starting buddy (buddy2) is #8 its order + * 1 buddy is #10: + * B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10 + * + * 2) Any buddy B will have an order O+1 parent P which + * satisfies the following equation: + * P = B & ~(1 << O) + * + * Assumption: *_mem_map is contiguous at least up to MAX_ORDER + */ +static inline unsigned long +__find_buddy_pfn(unsigned long page_pfn, unsigned int order) +{ + return page_pfn ^ (1 << order); +} + + +/* + * Find the buddy of @page and validate it. + * @page: The input page + * @order: The order of the input page + * + * The found buddy can be a non PageBuddy, out of @page's zone, or its order is + * not the same as @page. The validation is necessary before use it. + * + * Return: the found buddy page or NULL if not found. + */ +struct page *find_buddy_page_pfn(struct page *page, unsigned int order) +{ + unsigned long pfn = page_to_pfn(page); + unsigned long buddy_pfn = __find_buddy_pfn(pfn, order); + struct page *buddy = page + (buddy_pfn - pfn); + + if (page_is_buddy(page, buddy, order)) + return buddy; + return NULL; +} + /* * If this is not the largest possible page, check if the buddy * of the next-highest order is free. If it is, it's possible @@ -1010,18 +1055,16 @@ static inline bool buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn, struct page *page, unsigned int order) { - struct page *higher_page, *higher_buddy; - unsigned long combined_pfn; + struct page *higher_page; + unsigned long higher_page_pfn; if (order >= MAX_ORDER - 2) return false; - combined_pfn = buddy_pfn & pfn; - higher_page = page + (combined_pfn - pfn); - buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1); - higher_buddy = higher_page + (buddy_pfn - combined_pfn); + higher_page_pfn = buddy_pfn & pfn; + higher_page = page + (higher_page_pfn - pfn); - return page_is_buddy(higher_page, higher_buddy, order + 1); + return find_buddy_page_pfn(higher_page, order + 1) != NULL; } /* @@ -1075,11 +1118,11 @@ static inline void __free_one_page(struct page *page, migratetype); return; } - buddy_pfn = __find_buddy_pfn(pfn, order); - buddy = page + (buddy_pfn - pfn); - if (!page_is_buddy(page, buddy, order)) + buddy = find_buddy_page_pfn(page, order); + if (!buddy) goto done_merging; + buddy_pfn = page_to_pfn(buddy); if (unlikely(order >= pageblock_order)) { /* diff --git a/mm/page_isolation.c b/mm/page_isolation.c index f67c4c70f17f..7326c9f57d55 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -70,7 +70,6 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) unsigned long flags, nr_pages; bool isolated_page = false; unsigned int order; - unsigned long pfn, buddy_pfn; struct page *buddy; zone = page_zone(page); @@ -89,11 +88,8 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) if (PageBuddy(page)) { order = buddy_order(page); if (order >= pageblock_order && order < MAX_ORDER - 1) { - pfn = page_to_pfn(page); - buddy_pfn = __find_buddy_pfn(pfn, order); - buddy = page + (buddy_pfn - pfn); - - if (!is_migrate_isolate_page(buddy)) { + buddy = find_buddy_page_pfn(page, order); + if (buddy && !is_migrate_isolate_page(buddy)) { isolated_page = !!__isolate_free_page(page, order); /* * Isolating a free page in an isolated pageblock -- 2.35.1
