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

From: Zi Yan
Date: Thu Aug 11 2022 - 19:17:22 EST


From: Zi Yan <ziy@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
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