From: Joonsoo Kim iamjoonsoo.kim@lge.com

Currently, memalloc_nocma_{save/restore} API that prevents CMA area in page allocation is implemented by using current_gfp_context(). However, there are two problems of this implementation.

First, this doesn't work for allocation fastpath. In the fastpath, original gfp_mask is used since current_gfp_context() is introduced in order to control reclaim and it is on slowpath. So, CMA area can be allocated through the allocation fastpath even if memalloc_nocma_{save/restore} APIs are used. Currently, there is just one user for these APIs and it has a fallback method to prevent actual problem. Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect to exclude the memory on the ZONE_MOVABLE for allocation target.

To fix these problems, this patch changes the implementation to exclude CMA area in page allocation. Main point of this change is using the alloc_flags. alloc_flags is mainly used to control allocation so it fits for excluding CMA area in allocation.

Fixes: d7fefcc8de91 (mm/cma: add PF flag to force non cma alloc) Cc: stable@vger.kernel.org Signed-off-by: Joonsoo Kim iamjoonsoo.kim@lge.com --- include/linux/sched/mm.h | 8 +------- mm/page_alloc.c | 33 +++++++++++++++++++++++---------- 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 480a4d1..17e0c31 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -177,12 +177,10 @@ static inline bool in_vfork(struct task_struct *tsk) * Applies per-task gfp context to the given allocation flags. * PF_MEMALLOC_NOIO implies GFP_NOIO * PF_MEMALLOC_NOFS implies GFP_NOFS - * PF_MEMALLOC_NOCMA implies no allocation from CMA region. */ static inline gfp_t current_gfp_context(gfp_t flags) { - if (unlikely(current->flags & - (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_NOCMA))) { + if (unlikely(current->flags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS))) { /* * NOIO implies both NOIO and NOFS and it is a weaker context * so always make sure it makes precedence @@ -191,10 +189,6 @@ static inline gfp_t current_gfp_context(gfp_t flags) flags &= ~(__GFP_IO | __GFP_FS); else if (current->flags & PF_MEMALLOC_NOFS) flags &= ~__GFP_FS; -#ifdef CONFIG_CMA - if (current->flags & PF_MEMALLOC_NOCMA) - flags &= ~__GFP_MOVABLE; -#endif } return flags; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e028b87c..08cb35c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2790,7 +2790,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, * allocating from CMA when over half of the zone's free memory * is in the CMA area. */ - if (migratetype == MIGRATE_MOVABLE && + if (alloc_flags & ALLOC_CMA && zone_page_state(zone, NR_FREE_CMA_PAGES) > zone_page_state(zone, NR_FREE_PAGES) / 2) { page = __rmqueue_cma_fallback(zone, order); @@ -2801,7 +2801,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, retry: page = __rmqueue_smallest(zone, order, migratetype); if (unlikely(!page)) { - if (migratetype == MIGRATE_MOVABLE) + if (alloc_flags & ALLOC_CMA) page = __rmqueue_cma_fallback(zone, order);

if (!page && __rmqueue_fallback(zone, order, migratetype, @@ -3671,6 +3671,20 @@ alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask) return alloc_flags; }

+static inline unsigned int current_alloc_flags(gfp_t gfp_mask, + unsigned int alloc_flags) +{ +#ifdef CONFIG_CMA + unsigned int pflags = current->flags; + + if (!(pflags & PF_MEMALLOC_NOCMA) && + gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE) + alloc_flags |= ALLOC_CMA; + +#endif + return alloc_flags; +} + /* * get_page_from_freelist goes through the zonelist trying to allocate * a page. @@ -4316,10 +4330,8 @@ gfp_to_alloc_flags(gfp_t gfp_mask) } else if (unlikely(rt_task(current)) && !in_interrupt()) alloc_flags |= ALLOC_HARDER;

-#ifdef CONFIG_CMA - if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE) - alloc_flags |= ALLOC_CMA; -#endif + alloc_flags = current_alloc_flags(gfp_mask, alloc_flags); + return alloc_flags; }

@@ -4619,8 +4631,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, wake_all_kswapds(order, gfp_mask, ac);

reserve_flags = __gfp_pfmemalloc_flags(gfp_mask); - if (reserve_flags) + if (reserve_flags) { alloc_flags = reserve_flags; + alloc_flags = current_alloc_flags(gfp_mask, alloc_flags); + }

/* * Reset the nodemask and zonelist iterators if memory policies can be @@ -4697,7 +4711,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,

/* Avoid allocations with no watermarks from looping endlessly */ if (tsk_is_oom_victim(current) && - (alloc_flags == ALLOC_OOM || + (alloc_flags & ALLOC_OOM || (gfp_mask & __GFP_NOMEMALLOC))) goto nopage;

@@ -4785,8 +4799,7 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order, if (should_fail_alloc_page(gfp_mask, order)) return false;

- if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE) - *alloc_flags |= ALLOC_CMA; + *alloc_flags = current_alloc_flags(gfp_mask, *alloc_flags);

return true; }