[PATCH 1/1] mm/page_alloc: update comments in __free_pages_ok()

From: wonder_rock@126.com
To: akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Deyan Wang <wonder_rock@126.com>
Subject: [PATCH 1/1] mm/page_alloc: update comments in __free_pages_ok()
Date: Thu,  1 Dec 2022 21:50:45 +0800	[thread overview]
Message-ID: <20221201135045.31663-1-wonder_rock@126.com> (raw)

From: Deyan Wang <wonder_rock@126.com>

Add a comment to explain why we call get_pfnblock_migratetype() twice
in __free_pages_ok().

Signed-off-by: Deyan Wang <wonder_rock@126.com>
---
 mm/page_alloc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2d4c81224508..52dd4fff280b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1702,6 +1702,11 @@ static void __free_pages_ok(struct page *page, unsigned int order,
 	if (!free_pages_prepare(page, order, true, fpi_flags))
 		return;
 
+	/*
+	 * Calling get_pfnblock_migratetype() without spin_lock_irqsave() here
+	 * is used to avoid calling get_pfnblock_migratetype() under the lock.
+	 * This will reduce the lock holding time.
+	 */
 	migratetype = get_pfnblock_migratetype(page, pfn);
 
 	spin_lock_irqsave(&zone->lock, flags);
-- 
2.25.1

