linux-kernel - [PATCH 1/3] mm/page_alloc: correct start page when guard page debug is enabled

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Message-Id: <20230810095309.3109107-2-shikemeng@huaweicloud.com>
Date:   Thu, 10 Aug 2023 17:53:07 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, baolin.wang@...ux.alibaba.com,
        mgorman@...hsingularity.net, david@...hat.com, willy@...radead.org
Cc:     shikemeng@...weicloud.com
Subject: [PATCH 1/3] mm/page_alloc: correct start page when guard page debug is enabled

When guard page debug is enabled and set_page_guard returns success, we miss
to forward page to point to start of next split range and we will do split
unexpectedly in page range without target page. Move start page update
before set_page_guard to fix this.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 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 96b7c1a7d1f2..fd93d1396ccd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6557,6 +6557,7 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
 			next_page = page;
 			current_buddy = page + size;
 		}
+		page = next_page;
 
 		if (set_page_guard(zone, current_buddy, high, migratetype))
 			continue;
@@ -6564,7 +6565,6 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
 		if (current_buddy != target) {
 			add_to_free_list(current_buddy, zone, high, migratetype);
 			set_buddy_order(current_buddy, high);
-			page = next_page;
 		}
 	}
 }
-- 
2.30.0