linux-kernel - [PATCH 12/12] mm: compaction: make sure highest is above the min

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Date:   Mon, 18 Apr 2022 22:12:53 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <vbabka@...e.cz>, <pintu@...eaurora.org>,
        <charante@...eaurora.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH 12/12] mm: compaction: make sure highest is above the min_pfn

It's not guaranteed that highest will be above the min_pfn. If highest is
below the min_pfn, migrate_pfn and free_pfn can meet prematurely and lead
to some useless work. Make sure highest is above min_pfn to avoid making
a futile effort.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/compaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 609a76d7e051..65970107b789 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1532,7 +1532,7 @@ fast_isolate_freepages(struct compact_control *cc)
 			 * not found, be pessimistic for direct compaction
 			 * and use the min mark.
 			 */
-			if (highest) {
+			if (highest >= min_pfn) {
 				page = pfn_to_page(highest);
 				cc->free_pfn = highest;
 			} else {
-- 
2.23.0