linux-kernel - [RFC PATCH v2 05/12] mm: prevent pageblock size being larger than section size.

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Date:   Thu, 11 Aug 2022 19:16:36 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     linux-mm@...ck.org
Cc:     David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Yang Shi <shy828301@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 05/12] mm: prevent pageblock size being larger than section size.

From: Zi Yan <ziy@...dia.com>

Only physical pages from a section can be guaranteed to be contiguous
and so far a pageblock can only group contiguous physical pages by
design. Set pageblock_order properly to prevent pageblock going beyond
section size.

Signed-off-by: Zi Yan <ziy@...dia.com>
Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
 include/linux/pageblock-flags.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 358b871b07ca..2679b2b4c079 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -47,8 +47,11 @@ extern unsigned int pageblock_order;
 
 #else /* CONFIG_HUGETLB_PAGE */
 
-/* If huge pages are not used, group by MAX_ORDER_NR_PAGES */
-#define pageblock_order		MAX_ORDER
+/*
+ * If huge pages are not used, group by MAX_ORDER_NR_PAGES or
+ * PAGES_PER_SECTION when MAX_ORDER_NR_PAGES is larger.
+ */
+#define pageblock_order		(min(PFN_SECTION_SHIFT, MAX_ORDER))
 
 #endif /* CONFIG_HUGETLB_PAGE */
 
-- 
2.35.1