linux-kernel - [PATCH 6/8] mm: page_alloc: fix move_freepages

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Message-ID: <20230821183733.106619-7-hannes@cmpxchg.org>
Date:   Mon, 21 Aug 2023 14:33:38 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 6/8] mm: page_alloc: fix move_freepages_block() range error

When a block is partially outside the zone of the cursor page, the
function cuts the range to the pivot page instead of the zone
start. This can leave large parts of the block behind, which
encourages incompatible page mixing down the line (ask for one type,
get another), and thus long-term fragmentation.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6a4004f07123..6fcda8e96f16 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1697,7 +1697,7 @@ int move_freepages_block(struct zone *zone, struct page *page,
 
 	/* Do not cross zone boundaries */
 	if (!zone_spans_pfn(zone, start_pfn))
-		start_pfn = pfn;
+		start_pfn = zone->zone_start_pfn;
 	if (!zone_spans_pfn(zone, end_pfn))
 		return 0;
 
-- 
2.41.0