Commit 020396a5 authored by Johannes Weiner's avatar Johannes Weiner Committed by Andrew Morton
Browse files

mm: page_alloc: remove remnants of unlocked migratetype updates 

The freelist hygiene patches made migratetype accesses fully protected
under the zone->lock.  Remove remnants of handling the race conditions
that existed before from the MIGRATE_HIGHATOMIC code.

Link: https://lkml.kernel.org/r/20250225001023.1494422-3-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarBrendan Jackman <jackmanb@google.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c2f6ea38

mm/page_alloc.c

+16 −34
Original line number Diff line number Diff line
@@ -1991,20 +1991,10 @@ static inline bool boost_watermark(struct zone *zone) 
static struct page *

try_to_steal_block(struct zone *zone, struct page *page,

		   int current_order, int order, int start_type,

		   unsigned int alloc_flags)

		   int block_type, unsigned int alloc_flags)

{

	int free_pages, movable_pages, alike_pages;

	unsigned long start_pfn;

	int block_type;



	block_type = get_pageblock_migratetype(page);



	/*

	 * This can happen due to races and we want to prevent broken

	 * highatomic accounting.

	 */

	if (is_migrate_highatomic(block_type))

		return NULL;



	/* Take ownership for orders >= pageblock_order */

	if (current_order >= pageblock_order) {
@@ -2179,22 +2169,12 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, 
		spin_lock_irqsave(&zone->lock, flags);

		for (order = 0; order < NR_PAGE_ORDERS; order++) {

			struct free_area *area = &(zone->free_area[order]);

			int mt;

			unsigned long size;



			page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);

			if (!page)

				continue;



			mt = get_pageblock_migratetype(page);

			/*

			 * In page freeing path, migratetype change is racy so

			 * we can counter several free pages in a pageblock

			 * in this loop although we changed the pageblock type

			 * from highatomic to ac->migratetype. So we should

			 * adjust the count once.

			 */

			if (is_migrate_highatomic(mt)) {

				unsigned long size;

			/*

			 * It should never happen but changes to

			 * locking could inadvertently allow a per-cpu
@@ -2205,7 +2185,6 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, 
			size = max(pageblock_nr_pages, 1UL << order);

			size = min(size, zone->nr_reserved_highatomic);

			zone->nr_reserved_highatomic -= size;

			}



			/*

			 * Convert to ac->migratetype and avoid the normal
@@ -2217,10 +2196,12 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, 
			 * may increase.

			 */

			if (order < pageblock_order)

				ret = move_freepages_block(zone, page, mt,

				ret = move_freepages_block(zone, page,

							   MIGRATE_HIGHATOMIC,

							   ac->migratetype);

			else {

				move_to_free_list(page, zone, order, mt,

				move_to_free_list(page, zone, order,

						  MIGRATE_HIGHATOMIC,

						  ac->migratetype);

				change_pageblock_range(page, order,

						       ac->migratetype);
@@ -2294,7 +2275,8 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype, 


		page = get_page_from_free_area(area, fallback_mt);

		page = try_to_steal_block(zone, page, current_order, order,

					  start_migratetype, alloc_flags);

					  start_migratetype, fallback_mt,

					  alloc_flags);

		if (page)

			goto got_one;

	}