[PATCH v5 06/21] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page()

[Muchun Song]

In the later patch, we can use the free_vmemmap_page() to free the
unused vmemmap pages and initialize a page for vmemmap page using
via prepare_vmemmap_page().

Signed-off-by: Muchun Song <songmuc...@bytedance.com>
---
 include/linux/bootmem_info.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
index 4ed6dee1adc9..239e3cc8f86c 100644
--- a/include/linux/bootmem_info.h
+++ b/include/linux/bootmem_info.h
@@ -3,6 +3,7 @@
 #define __LINUX_BOOTMEM_INFO_H
 
 #include <linux/mmzone.h>
+#include <linux/mm.h>
 
 /*
  * Types for free bootmem stored in page->lru.next. These have to be in
@@ -22,6 +23,29 @@ void __init register_page_bootmem_info_node(struct 
pglist_data *pgdat);
 void get_page_bootmem(unsigned long info, struct page *page,
                      unsigned long type);
 void put_page_bootmem(struct page *page);
+
+static inline void free_vmemmap_page(struct page *page)
+{
+       VM_WARN_ON(!PageReserved(page) || page_ref_count(page) != 2);
+
+       /* bootmem page has reserved flag in the reserve_bootmem_region */
+       if (PageReserved(page)) {
+               unsigned long magic = (unsigned long)page->freelist;
+
+               if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
+                       put_page_bootmem(page);
+               else
+                       WARN_ON(1);
+       }
+}
+
+static inline void prepare_vmemmap_page(struct page *page)
+{
+       unsigned long section_nr = pfn_to_section_nr(page_to_pfn(page));
+
+       get_page_bootmem(section_nr, page, SECTION_INFO);
+       mark_page_reserved(page);
+}
 #else
 static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
 {
-- 
2.11.0