bootmem: stop using page->index

Encode the type into the bottom four bits of page->private and the info
into the remaining bits.  Also turn the bootmem type into a named enum.

[arnd@arndb.de: bootmem: add bootmem_type stub function]
  Link: https://lkml.kernel.org/r/20241015143802.577613-1-arnd@kernel.org
[akpm@linux-foundation.org: fix build with !CONFIG_HAVE_BOOTMEM_INFO_NODE]
 Link: https://lore.kernel.org/oe-kbuild-all/202410090311.eaqcL7IZ-lkp@intel.com/
Link: https://lkml.kernel.org/r/20241005200121.3231142-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 27 insertions, 8 deletions

diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
index cffa38a73618..d8a8d245824a 100644
--- a/include/linux/bootmem_info.h
+++ b/include/linux/bootmem_info.h
@@ -6,11 +6,10 @@
 #include <linux/kmemleak.h>
 
 /*
- * Types for free bootmem stored in page->lru.next. These have to be in
- * some random range in unsigned long space for debugging purposes.
+ * Types for free bootmem stored in the low bits of page->private.
  */
-enum {
-	MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE = 12,
+enum bootmem_type {
+	MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE = 1,
 	SECTION_INFO = MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE,
 	MIX_SECTION_INFO,
 	NODE_INFO,
@@ -21,9 +20,19 @@ enum {
 void __init register_page_bootmem_info_node(struct pglist_data *pgdat);
 
 void get_page_bootmem(unsigned long info, struct page *page,
-		      unsigned long type);
+		enum bootmem_type type);
 void put_page_bootmem(struct page *page);
 
+static inline enum bootmem_type bootmem_type(const struct page *page)
+{
+	return (unsigned long)page->private & 0xf;
+}
+
+static inline unsigned long bootmem_info(const struct page *page)
+{
+	return (unsigned long)page->private >> 4;
+}
+
 /*
  * Any memory allocated via the memblock allocator and not via the
  * buddy will be marked reserved already in the memmap. For those
@@ -31,7 +40,7 @@ void put_page_bootmem(struct page *page);
  */
 static inline void free_bootmem_page(struct page *page)
 {
-	unsigned long magic = page->index;
+	enum bootmem_type type = bootmem_type(page);
 
 	/*
 	 * The reserve_bootmem_region sets the reserved flag on bootmem
@@ -39,7 +48,7 @@ static inline void free_bootmem_page(struct page *page)
 	 */
 	VM_BUG_ON_PAGE(page_ref_count(page) != 2, page);
 
-	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
+	if (type == SECTION_INFO || type == MIX_SECTION_INFO)
 		put_page_bootmem(page);
 	else
 		VM_BUG_ON_PAGE(1, page);
@@ -53,8 +62,18 @@ static inline void put_page_bootmem(struct page *page)
 {
 }
 
+static inline enum bootmem_type bootmem_type(const struct page *page)
+{
+	return SECTION_INFO;
+}
+
+static inline unsigned long bootmem_info(const struct page *page)
+{
+	return 0;
+}
+
 static inline void get_page_bootmem(unsigned long info, struct page *page,
-				    unsigned long type)
+				    enum bootmem_type type)
 {
 }