[RFC PATCH 06/15] mm: use PAGES_PER_SECTION instead for mem_map_offset/next().

From: Zi Yan <zi.yan@sent.com>
To: David Hildenbrand <david@redhat.com>, linux-mm@kvack.org
Cc: Matthew Wilcox <willy@infradead.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Michal Hocko <mhocko@kernel.org>,
	John Hubbard <jhubbard@nvidia.com>,
	linux-kernel@vger.kernel.org, Zi Yan <ziy@nvidia.com>
Subject: [RFC PATCH 06/15] mm: use PAGES_PER_SECTION instead for mem_map_offset/next().
Date: Thu,  5 Aug 2021 15:02:44 -0400	[thread overview]
Message-ID: <20210805190253.2795604-7-zi.yan@sent.com> (raw)
In-Reply-To: <20210805190253.2795604-1-zi.yan@sent.com>

From: Zi Yan <ziy@nvidia.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@nvidia.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.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

