linux-kernel - [PATCH 2/3] mm: page_isolation: remove unnecessary freepage

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Message-id: <000201d01385$25a6c950$70f45bf0$%yang@samsung.com>
Date:	Tue, 09 Dec 2014 15:51:49 +0800
From:	Weijie Yang <weijie.yang@...sung.com>
To:	iamjoonsoo.kim@....com
Cc:	'Andrew Morton' <akpm@...ux-foundation.org>, mgorman@...e.de,
	'Rik van Riel' <riel@...hat.com>, vbabka@...e.cz,
	'Johannes Weiner' <hannes@...xchg.org>,
	'Minchan Kim' <minchan@...nel.org>,
	'Weijie Yang' <weijie.yang.kh@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 2/3] mm: page_isolation: remove unnecessary
 freepage_migratetype check for unused page

when we test the pages in a range is free or not, there is a little
chance we encounter some page which is not in buddy but page_count is 0.
That means that page could be in the page-freeing path but not in the
buddy freelist, such as in pcplist or wait for the zone->lock which the
tester is holding.

Back to the freepage_migratetype, we use it for a cached value for decide
which free-list the page go when freeing page. If the pageblock is isolated
the page will go to free-list[MIGRATE_ISOLATE] even if the cached type is
not MIGRATE_ISOLATE, the commit ad53f92e(fix incorrect isolation behavior
by rechecking migratetype) patch series have ensure this.

So the freepage_migratetype check for page_count==0 page in
__test_page_isolated_in_pageblock() is meaningless.
This patch removes the unnecessary freepage_migratetype check.

Signed-off-by: Weijie Yang <weijie.yang@...sung.com>
---
 mm/page_isolation.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 6e5174d..f7c9183 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -223,8 +223,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 		page = pfn_to_page(pfn);
 		if (PageBuddy(page))
 			pfn += 1 << page_order(page);
-		else if (page_count(page) == 0 &&
-			get_freepage_migratetype(page) == MIGRATE_ISOLATE)
+		else if (page_count(page) == 0)
 			pfn += 1;
 		else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
 			/*
-- 
1.7.10.4

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