For the MIGRATE_RESERVE pages, it is important they do not get misplaced on free_list of other migratetype, otherwise the whole MIGRATE_RESERVE pageblock might be changed to other migratetype in try_to_steal_freepages(). For MIGRATE_CMA, the pages also must not go to a different free_list, otherwise they could get allocated as unmovable and result in CMA failure.
This is ensured by setting the freepage_migratetype appropriately when placing pages on pcp lists, and using the information when releasing them back to free_list. It is also assumed that CMA and RESERVE pageblocks are created only in the init phase. This patch adds DEBUG_VM checks to catch any regressions introduced for this invariant. Cc: Yong-Taek Lee <[email protected]> Cc: Bartlomiej Zolnierkiewicz <[email protected]> Cc: Joonsoo Kim <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Minchan Kim <[email protected]> Cc: KOSAKI Motohiro <[email protected]> Cc: Marek Szyprowski <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Michal Nazarewicz <[email protected]> Signed-off-by: Vlastimil Babka <[email protected]> --- include/linux/mm.h | 19 +++++++++++++++++++ mm/page_alloc.c | 3 +++ 2 files changed, 22 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index c1b7414..27a74ba 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -280,6 +280,25 @@ static inline int get_freepage_migratetype(struct page *page) } /* + * Check that a freepage cannot end up on a wrong free_list for "sensitive" + * migratetypes. Return false if it could. Useful for VM_BUG_ON checks. + */ +static inline bool check_freepage_migratetype(struct page *page) +{ + int pageblock_mt = get_pageblock_migratetype(page); + int freepage_mt = get_freepage_migratetype(page); + + /* + * For RESERVE and CMA pageblocks, the freepage_migratetype must + * match their migratetype. For other pageblocks, we don't care. + */ + if (pageblock_mt != MIGRATE_RESERVE && !is_migrate_cma(pageblock_mt)) + return true; + + return (freepage_mt == pageblock_mt); +} + +/* * FIXME: take this include out, include page-flags.h in * files which need it (119 of them) */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2dbaba1..0ee9f8c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -697,6 +697,8 @@ static void free_pcppages_bulk(struct zone *zone, int count, page = list_entry(list->prev, struct page, lru); /* must delete as __free_one_page list manipulates */ list_del(&page->lru); + + VM_BUG_ON(!check_freepage_migratetype(page)); mt = get_freepage_migratetype(page); /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ __free_one_page(page, zone, 0, mt); @@ -1190,6 +1192,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, struct page *page = __rmqueue(zone, order, migratetype); if (unlikely(page == NULL)) break; + VM_BUG_ON(!check_freepage_migratetype(page)); /* * Split buddy pages returned by expand() are received here -- 1.8.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
