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From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	Zi Yan <ziy@nvidia.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	David Hildenbrand <david@redhat.com>,
	linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 08/10] mm: page_alloc: set migratetype inside move_freepages()
Date: Wed, 20 Mar 2024 14:02:13 -0400
Message-ID: <20240320180429.678181-9-hannes@cmpxchg.org>
In-Reply-To: <20240320180429.678181-1-hannes@cmpxchg.org>
References: <20240320180429.678181-1-hannes@cmpxchg.org>
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From: Zi Yan <ziy@nvidia.com>

This avoids changing migratetype after move_freepages() or
move_freepages_block(), which is error prone. It also prepares for
upcoming changes to fix move_freepages() not moving free pages
partially in the range.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/page_alloc.c     | 27 +++++++++++++--------------
 mm/page_isolation.c |  7 +++----
 2 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3f65b565eaad..d687f27d891f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1581,9 +1581,8 @@ static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
 #endif
 
 /*
- * Move the free pages in a range to the freelist tail of the requested type.
- * Note that start_page and end_pages are not aligned on a pageblock
- * boundary. If alignment is required, use move_freepages_block()
+ * Change the type of a block and move all its free pages to that
+ * type's freelist.
  */
 static int move_freepages(struct zone *zone, unsigned long start_pfn,
 			  unsigned long end_pfn, int migratetype)
@@ -1593,6 +1592,9 @@ static int move_freepages(struct zone *zone, unsigned long start_pfn,
 	unsigned int order;
 	int pages_moved = 0;
 
+	VM_WARN_ON(start_pfn & (pageblock_nr_pages - 1));
+	VM_WARN_ON(start_pfn + pageblock_nr_pages - 1 != end_pfn);
+
 	for (pfn = start_pfn; pfn <= end_pfn;) {
 		page = pfn_to_page(pfn);
 		if (!PageBuddy(page)) {
@@ -1610,6 +1612,8 @@ static int move_freepages(struct zone *zone, unsigned long start_pfn,
 		pages_moved += 1 << order;
 	}
 
+	set_pageblock_migratetype(pfn_to_page(start_pfn), migratetype);
+
 	return pages_moved;
 }
 
@@ -1837,7 +1841,6 @@ steal_suitable_fallback(struct zone *zone, struct page *page,
 	if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
 			page_group_by_mobility_disabled) {
 		move_freepages(zone, start_pfn, end_pfn, start_type);
-		set_pageblock_migratetype(page, start_type);
 		return __rmqueue_smallest(zone, order, start_type);
 	}
 
@@ -1911,12 +1914,10 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone)
 	/* Yoink! */
 	mt = get_pageblock_migratetype(page);
 	/* Only reserve normal pageblocks (i.e., they can merge with others) */
-	if (migratetype_is_mergeable(mt)) {
-		if (move_freepages_block(zone, page, MIGRATE_HIGHATOMIC) != -1) {
-			set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
+	if (migratetype_is_mergeable(mt))
+		if (move_freepages_block(zone, page,
+					 MIGRATE_HIGHATOMIC) != -1)
 			zone->nr_reserved_highatomic += pageblock_nr_pages;
-		}
-	}
 
 out_unlock:
 	spin_unlock_irqrestore(&zone->lock, flags);
@@ -1995,7 +1996,6 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
 			 * not fail on zone boundaries.
 			 */
 			WARN_ON_ONCE(ret == -1);
-			set_pageblock_migratetype(page, ac->migratetype);
 			if (ret > 0) {
 				spin_unlock_irqrestore(&zone->lock, flags);
 				return ret;
@@ -2711,10 +2711,9 @@ int __isolate_free_page(struct page *page, unsigned int order)
 			 * Only change normal pageblocks (i.e., they can merge
 			 * with others)
 			 */
-			if (migratetype_is_mergeable(mt) &&
-			    move_freepages_block(zone, page,
-						 MIGRATE_MOVABLE) != -1)
-				set_pageblock_migratetype(page, MIGRATE_MOVABLE);
+			if (migratetype_is_mergeable(mt))
+				move_freepages_block(zone, page,
+						     MIGRATE_MOVABLE);
 		}
 	}
 
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 71539d7b96cf..f84f0981b2df 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -188,7 +188,6 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
 			return -EBUSY;
 		}
 		__mod_zone_freepage_state(zone, -nr_pages, mt);
-		set_pageblock_migratetype(page, MIGRATE_ISOLATE);
 		zone->nr_isolate_pageblock++;
 		spin_unlock_irqrestore(&zone->lock, flags);
 		return 0;
@@ -262,10 +261,10 @@ static void unset_migratetype_isolate(struct page *page, int migratetype)
 		 */
 		WARN_ON_ONCE(nr_pages == -1);
 		__mod_zone_freepage_state(zone, nr_pages, migratetype);
-	}
-	set_pageblock_migratetype(page, migratetype);
-	if (isolated_page)
+	} else {
+		set_pageblock_migratetype(page, migratetype);
 		__putback_isolated_page(page, order, migratetype);
+	}
 	zone->nr_isolate_pageblock--;
 out:
 	spin_unlock_irqrestore(&zone->lock, flags);
-- 
2.44.0