Pages on CMA area could have MIGRATE_ISOLATE as well as MIGRATE_CMA so current is_pinnable_page could miss CMA pages which has MIGRATE_ ISOLATE. It ends up putting CMA pages longterm pinning possible on pin_user_pages APIs so CMA allocation fails. The CMA allocation path protects the migration type change race using zone->lock but what GUP path need to know is just whether the page is on CMA area or not rather than exact type. Thus, we don't need zone->lock but just checks the migratype in either of (MIGRATE_ISOLATE and MIGRATE_CMA). Adding the MIGRATE_ISOLATE check in is_pinnable_page could cause rejecting of pinning the page on MIGRATE_ISOLATE pageblock even thouth it's neither CMA nor movable zone if the page is temporarily unmovable. However, the migration failure is general issue, not only come from MIGRATE_ISOLATE and the MIGRATE_ISOLATE is also transient state like other temporal refcount holding of pages. Cc: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- * from v2 - https://lore.kernel.org/all/20220505064429.2818496-1-minchan@xxxxxxxxxx/ * Use __READ_ONCE instead of volatile - akpm * from v1 - https://lore.kernel.org/all/20220502173558.2510641-1-minchan@xxxxxxxxxx/ * fix build warning - lkp * fix refetching issue of migration type * add side effect on !ZONE_MOVABLE and !MIGRATE_CMA in description - david include/linux/mm.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6acca5cecbc5..cbf79eb790e0 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1625,8 +1625,19 @@ static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, #ifdef CONFIG_MIGRATION static inline bool is_pinnable_page(struct page *page) { - return !(is_zone_movable_page(page) || is_migrate_cma_page(page)) || - is_zero_pfn(page_to_pfn(page)); +#ifdef CONFIG_CMA + /* + * use volatile to use local variable mt instead of + * refetching mt value. + */ + int __mt = get_pageblock_migratetype(page); + int mt = __READ_ONCE(__mt); + + if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE) + return false; +#endif + + return !(is_zone_movable_page(page) || is_zero_pfn(page_to_pfn(page))); } #else static inline bool is_pinnable_page(struct page *page) -- 2.36.0.512.ge40c2bad7a-goog
