[PATCH v3 07/21] mm/bootmem_info: Combine bootmem info and type into page->freelist

[Muchun Song]

The page->private shares storage with page->ptl. In the later patch,
we will use the page->ptl. So here we combine bootmem info and type
into page->freelist so that we can do not use page->private.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/bootmem_info.h | 18 ++++++++++++++++--
 mm/bootmem_info.c            | 12 ++++++------
 mm/sparse.c                  |  4 ++--
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
index ce9d8c97369d..b5786a8b412e 100644
--- a/include/linux/bootmem_info.h
+++ b/include/linux/bootmem_info.h
@@ -6,7 +6,7 @@
 #include <linux/mm.h>
 
 /*
- * Types for free bootmem stored in page->lru.next. These have to be in
+ * Types for free bootmem stored in page->freelist. These have to be in
  * some random range in unsigned long space for debugging purposes.
  */
 enum {
@@ -17,6 +17,20 @@ enum {
 	MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE = NODE_INFO,
 };
 
+#define BOOTMEM_TYPE_BITS	4
+#define BOOTMEM_TYPE_MAX	((1UL << BOOTMEM_TYPE_BITS) - 1)
+#define BOOTMEM_INFO_MAX	(ULONG_MAX >> BOOTMEM_TYPE_BITS)
+
+static inline unsigned long page_bootmem_type(struct page *page)
+{
+	return (unsigned long)page->freelist & BOOTMEM_TYPE_MAX;
+}
+
+static inline unsigned long page_bootmem_info(struct page *page)
+{
+	return (unsigned long)page->freelist >> BOOTMEM_TYPE_BITS;
+}
+
 #ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
 void __init register_page_bootmem_info_node(struct pglist_data *pgdat);
 
@@ -30,7 +44,7 @@ static inline void free_vmemmap_page(struct page *page)
 
 	/* bootmem page has reserved flag in the reserve_bootmem_region */
 	if (PageReserved(page)) {
-		unsigned long magic = (unsigned long)page->freelist;
+		unsigned long magic = page_bootmem_type(page);
 
 		if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
 			put_page_bootmem(page);
diff --git a/mm/bootmem_info.c b/mm/bootmem_info.c
index fcab5a3f8cc0..9baf163965fd 100644
--- a/mm/bootmem_info.c
+++ b/mm/bootmem_info.c
@@ -12,9 +12,9 @@
 
 void get_page_bootmem(unsigned long info, struct page *page, unsigned long type)
 {
-	page->freelist = (void *)type;
-	SetPagePrivate(page);
-	set_page_private(page, info);
+	BUG_ON(info > BOOTMEM_INFO_MAX);
+	BUG_ON(type > BOOTMEM_TYPE_MAX);
+	page->freelist = (void *)((info << BOOTMEM_TYPE_BITS) | type);
 	page_ref_inc(page);
 }
 
@@ -22,14 +22,12 @@ void put_page_bootmem(struct page *page)
 {
 	unsigned long type;
 
-	type = (unsigned long) page->freelist;
+	type = page_bootmem_type(page);
 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
 	       type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
 
 	if (page_ref_dec_return(page) == 1) {
 		page->freelist = NULL;
-		ClearPagePrivate(page);
-		set_page_private(page, 0);
 		INIT_LIST_HEAD(&page->lru);
 		free_reserved_page(page);
 	}
@@ -101,6 +99,8 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
 	int node = pgdat->node_id;
 	struct page *page;
 
+	BUILD_BUG_ON(MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE > BOOTMEM_TYPE_MAX);
+
 	nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
 	page = virt_to_page(pgdat);
 
diff --git a/mm/sparse.c b/mm/sparse.c
index a4138410d890..fca5fa38c2bc 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -740,12 +740,12 @@ static void free_map_bootmem(struct page *memmap)
 		>> PAGE_SHIFT;
 
 	for (i = 0; i < nr_pages; i++, page++) {
-		magic = (unsigned long) page->freelist;
+		magic = page_bootmem_type(page);
 
 		BUG_ON(magic == NODE_INFO);
 
 		maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
-		removing_section_nr = page_private(page);
+		removing_section_nr = page_bootmem_info(page);
 
 		/*
 		 * When this function is called, the removing section is
-- 
2.11.0