Commit f945116e authored by Johannes Weiner's avatar Johannes Weiner Committed by Andrew Morton
Browse files

mm: page_alloc: remove stale CMA guard code 

In the past, movable allocations could be disallowed from CMA through
PF_MEMALLOC_PIN.  As CMA pages are funneled through the MOVABLE pcplist,
this required filtering that cornercase during allocations, such that
pinnable allocations wouldn't accidentally get a CMA page.

However, since 8e3560d9 ("mm: honor PF_MEMALLOC_PIN for all movable
pages"), PF_MEMALLOC_PIN automatically excludes __GFP_MOVABLE.  Once
again, MOVABLE implies CMA is allowed.

Remove the stale filtering code.  Also remove a stale comment that was
introduced as part of the filtering code, because the filtering let
order-0 pages fall through to the buddy allocator.  See 1d91df85
("mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore}
APIs") for context.  The comment's been obsolete since the introduction of
the explicit ALLOC_HIGHATOMIC flag in eb2e2b42 ("mm/page_alloc:
explicitly record high-order atomic allocations in alloc_flags").

Link: https://lkml.kernel.org/r/20230824153821.243148-1-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 12af80f6

mm/page_alloc.c

+4 −17
Original line number Diff line number Diff line
@@ -2641,12 +2641,6 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, 
	do {

		page = NULL;

		spin_lock_irqsave(&zone->lock, flags);

		/*

		 * 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 (alloc_flags & ALLOC_HIGHATOMIC)

			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);

		if (!page) {
@@ -2780,18 +2774,11 @@ struct page *rmqueue(struct zone *preferred_zone, 
	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));



	if (likely(pcp_allowed_order(order))) {

		/*

		 * 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, order,

				       migratetype, alloc_flags);

		if (likely(page))

			goto out;

	}

	}



	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,

							migratetype);