From 1d91df85f399adbe4f318f3e74ac5a5d84c0ca7c Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Fri, 2 Oct 2020 22:21:45 -0700 Subject: [PATCH] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs memalloc_nocma_{save/restore} APIs can be used to skip page allocation on CMA area, but, there is a missing case and the page on CMA area could be allocated even if APIs are used. This patch handles this case to fix the potential issue. For now, these APIs are used to prevent long-term pinning on the CMA page. When the long-term pinning is requested on the CMA page, it is migrated to the non-CMA page before pinning. This non-CMA page is allocated by using memalloc_nocma_{save/restore} APIs. If APIs doesn't work as intended, the CMA page is allocated and it is pinned for a long time. This long-term pin for the CMA page causes cma_alloc() failure and it could result in wrong behaviour on the device driver who uses the cma_alloc(). Missing case is an allocation from the pcplist. MIGRATE_MOVABLE pcplist could have the pages on CMA area so we need to skip it if ALLOC_CMA isn't specified. Fixes: 8510e69c8efe (mm/page_alloc: fix memalloc_nocma_{save/restore} APIs) Signed-off-by: Joonsoo Kim Signed-off-by: Andrew Morton Acked-by: Vlastimil Babka Acked-by: Michal Hocko Cc: "Aneesh Kumar K . V" Cc: Mel Gorman Link: https://lkml.kernel.org/r/1601429472-12599-1-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5661fa164f1308..6866533de8e6a5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3367,9 +3367,16 @@ struct page *rmqueue(struct zone *preferred_zone, struct page *page; if (likely(order == 0)) { - page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, + /* + * MIGRATE_MOVABLE pcplist could have the pages on CMA area and + * we need to skip it when CMA area isn't allowed. + */ + if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA || + migratetype != MIGRATE_MOVABLE) { + page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, migratetype, alloc_flags); - goto out; + goto out; + } } /* @@ -3381,7 +3388,13 @@ struct page *rmqueue(struct zone *preferred_zone, do { page = NULL; - if (alloc_flags & ALLOC_HARDER) { + /* + * order-0 request can reach here when the pcplist is skipped + * due to non-CMA allocation context. HIGHATOMIC area is + * reserved for high-order atomic allocation, so order-0 + * request should skip it. + */ + if (order > 0 && alloc_flags & ALLOC_HARDER) { page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); if (page) trace_mm_page_alloc_zone_locked(page, order, migratetype);