linux-kernel - [PATCH] mm/isolate: Drop pre-validating migrate type in undo_isolate_page

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Message-Id: <1562307161-30554-1-git-send-email-anshuman.khandual@arm.com>
Date:   Fri,  5 Jul 2019 11:42:41 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>, Qian Cai <cai@....pw>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/isolate: Drop pre-validating migrate type in undo_isolate_page_range()

unset_migratetype_isolate() already validates under zone lock that a given
page has already been isolated as MIGRATE_ISOLATE. There is no need for
another check before. Hence just drop this redundant validation.

Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Qian Cai <cai@....pw>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org

Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
Is there any particular reason to do this migratetype pre-check without zone
lock before calling unsert_migrate_isolate() ? If not this should be removed.

 mm/page_isolation.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index e3638a5bafff..f529d250c8a5 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -243,7 +243,7 @@ int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 	     pfn < end_pfn;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
-		if (!page || !is_migrate_isolate_page(page))
+		if (!page)
 			continue;
 		unset_migratetype_isolate(page, migratetype);
 	}
-- 
2.20.1