From ac7ec62d355657de57e590db0cf79477a615bfd8 Mon Sep 17 00:00:00 2001
From: Jesse Tannahill <jesset@codeaurora.org>
Date: Fri, 9 Jul 2010 18:18:05 -0700
Subject: [PATCH] mm: Make memory hotplug aware of memmap holes

This patch prevents memory hotplug from marking pages of the memmap that
only reference holes in the physical address space as private. Some
architectures (including ARM) attempt to free these unneeded parts of the
memmap, and attempting to free a private page will throw bad_page warnings
and tie up the memory indefinitely.

This patch also allows early_pfn_valid to be architecture specific and
defines it for ARM. The definition for ARM takes into account memory banks
and the holes in physical memory.

CRs-Fixed: 247010

Change-Id: Iad88d427b1b923a808b026c22d2899fa0483cb9e
Signed-off-by: jesset@codeaurora.org
(cherry picked from commit 0b610c773ad6281a3d217fbbe894b2476e9e71dd)

Conflicts:

	arch/arm/mm/init.c
---
 arch/arm/include/asm/page.h |  5 +++++
 arch/arm/mm/init.c          | 22 ++++++++++++++++++++++
 include/linux/mmzone.h      |  3 +++
 mm/memory_hotplug.c         | 23 ++++++++++++++++++-----
 4 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index 812a4944e783..3c4db965c8d4 100644
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -158,6 +158,11 @@ typedef struct page *pgtable_t;
 extern int pfn_valid(unsigned long);
 #endif
 
+#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
+extern int _early_pfn_valid(unsigned long);
+#define early_pfn_valid(pfn) (_early_pfn_valid(pfn))
+#endif
+
 #include <asm/memory.h>
 
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 25333bf9884b..c5d5441bf579 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -423,6 +423,28 @@ void __init arm_memblock_init(struct meminfo *mi, struct machine_desc *mdesc)
 	memblock_dump_all();
 }
 
+#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
+int _early_pfn_valid(unsigned long pfn)
+{
+	struct meminfo *mi = &meminfo;
+	unsigned int left = 0, right = mi->nr_banks;
+
+	do {
+		unsigned int mid = (right + left) / 2;
+		struct membank *bank = &mi->bank[mid];
+
+		if (pfn < bank_pfn_start(bank))
+			right = mid;
+		else if (pfn >= bank_pfn_end(bank))
+			left = mid + 1;
+		else
+			return 1;
+	} while (left < right);
+	return 0;
+}
+EXPORT_SYMBOL(_early_pfn_valid);
+#endif
+
 void __init bootmem_init(void)
 {
 	unsigned long min, max_low, max_high;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 5c76737d836b..b1cbf658de46 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1212,7 +1212,10 @@ static inline int pfn_present(unsigned long pfn)
 #define pfn_to_nid(pfn)		(0)
 #endif
 
+#ifndef early_pfn_valid
 #define early_pfn_valid(pfn)	pfn_valid(pfn)
+#endif
+
 void sparse_init(void);
 #else
 #define sparse_init()	do {} while (0)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a48c432ff86c..16001a7a1bb7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -133,9 +133,10 @@ void __ref put_page_bootmem(struct page *page)
 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 static void register_page_bootmem_info_section(unsigned long start_pfn)
 {
-	unsigned long *usemap, mapsize, section_nr, i;
+	unsigned long *usemap, mapsize, page_mapsize, section_nr, i, j;
 	struct mem_section *ms;
-	struct page *page, *memmap;
+	struct page *page, *memmap, *page_page;
+	int memmap_page_valid;
 
 	section_nr = pfn_to_section_nr(start_pfn);
 	ms = __nr_to_section(section_nr);
@@ -151,9 +152,21 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
 	mapsize = sizeof(struct page) * PAGES_PER_SECTION;
 	mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
 
-	/* remember memmap's page */
-	for (i = 0; i < mapsize; i++, page++)
-		get_page_bootmem(section_nr, page, SECTION_INFO);
+	page_mapsize = PAGE_SIZE/sizeof(struct page);
+
+	/* remember memmap's page, except those that reference only holes */
+	for (i = 0; i < mapsize; i++, page++) {
+		memmap_page_valid = 0;
+		page_page = __va(page_to_pfn(page) << PAGE_SHIFT);
+		for (j = 0; j < page_mapsize; j++, page_page++) {
+			if (early_pfn_valid(page_to_pfn(page_page))) {
+				memmap_page_valid = 1;
+				break;
+			}
+		}
+		if (memmap_page_valid)
+			get_page_bootmem(section_nr, page, SECTION_INFO);
+	}
 
 	usemap = __nr_to_section(section_nr)->pageblock_flags;
 	page = virt_to_page(usemap);