linux-kernel - [RFC PATCH 06/15] mm: use PAGES_PER_SECTION instead for mem_map

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Message-Id: <20210805190253.2795604-7-zi.yan@sent.com>
Date:   Thu,  5 Aug 2021 15:02:44 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc:     Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...nel.org>,
        John Hubbard <jhubbard@...dia.com>,
        linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>
Subject: [RFC PATCH 06/15] mm: use PAGES_PER_SECTION instead for mem_map_offset/next().

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

mem_map is only guaranteed to be virtually contiguous within a
section, so mem_map_offset/next() uses pfn to handle mem_map
discontiguity. Use PAGES_PER_SECTION instead of MAX_ORDER_NR_PAGES to
describe this condition more precisely.

Signed-off-by: Zi Yan <ziy@...dia.com>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
 mm/internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index b1001ebeb286..4ca52c696902 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -485,7 +485,7 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
  */
 static inline struct page *mem_map_offset(struct page *base, int offset)
 {
-	if (unlikely(offset >= MAX_ORDER_NR_PAGES))
+	if (unlikely(offset >= PAGES_PER_SECTION))
 		return nth_page(base, offset);
 	return base + offset;
 }
@@ -497,7 +497,7 @@ static inline struct page *mem_map_offset(struct page *base, int offset)
 static inline struct page *mem_map_next(struct page *iter,
 						struct page *base, int offset)
 {
-	if (unlikely((offset & (MAX_ORDER_NR_PAGES - 1)) == 0)) {
+	if (unlikely((offset & (PAGES_PER_SECTION - 1)) == 0)) {
 		unsigned long pfn = page_to_pfn(base) + offset;
 		if (!pfn_valid(pfn))
 			return NULL;
-- 
2.30.2