linux-kernel - [PATCH 1/2] linux: sparsemem: Initialize all memmap entries within sections

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Message-Id: <20120329190113.3891.38390934@jp.panasonic.com>
Date:	Thu, 29 Mar 2012 19:01:13 +0900
From:	Akira Takeuchi <takeuchi.akr@...panasonic.com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] linux: sparsemem: Initialize all memmap entries within sections

This commit fixes the problem for the kernel
with CONFIG_SPARSEMEM=y and CONFIG_HAVE_ARCH_PFN_VALID=y.

VM subsystem insists that memmap entries within the align to MAX_ORDER_NR_PAGES
must exist and be initialized.

However, in the kernel with CONFIG_SPARSEMEM=y and CONFIG_HAVE_ARCH_PFN_VALID=y,
the kernel only initializes the entries corresponding to the memory regions
specified by "mem=" options. This causes "kernel BUG at mm/page_alloc.c:777!"
This BUG message comes from the following BUG_ON() line in move_freepages().

    BUG_ON(page_zone(start_page) != page_zone(end_page));

Signed-off-by: Akira Takeuchi <takeuchi.akr@...panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@...panasonic.com>
---
 include/linux/mmzone.h |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index dff7115..1b7538c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1088,13 +1088,15 @@ static inline struct mem_section *__pfn_to_section(unsigned long pfn)
 	return __nr_to_section(pfn_to_section_nr(pfn));
 }
 
-#ifndef CONFIG_HAVE_ARCH_PFN_VALID
-static inline int pfn_valid(unsigned long pfn)
+static inline int sparsemem_pfn_valid(unsigned long pfn)
 {
 	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
 		return 0;
 	return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
 }
+
+#ifndef CONFIG_HAVE_ARCH_PFN_VALID
+#define pfn_valid(pfn) sparsemem_pfn_valid(pfn)
 #endif
 
 static inline int pfn_present(unsigned long pfn)
@@ -1119,7 +1121,7 @@ static inline int pfn_present(unsigned long pfn)
 #define pfn_to_nid(pfn)		(0)
 #endif
 
-#define early_pfn_valid(pfn)	pfn_valid(pfn)
+#define early_pfn_valid(pfn)	sparsemem_pfn_valid(pfn)
 void sparse_init(void);
 #else
 #define sparse_init()	do {} while (0)
-- 
1.7.4.1


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