[PATCH v3 1/3] mm/memblock: introduce a new helper memblock_estimated_nr_pages()

[Wei Yang <richard.weiyang@gmail.com>]

Instead of using raw memblock api, we wrap a new helper for user.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
 include/linux/memblock.h |  1 +
 mm/memblock.c            | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 40c62aca36ec..7d1c32b3dc12 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -486,6 +486,7 @@ static inline __init_memblock bool memblock_bottom_up(void)
 
 phys_addr_t memblock_phys_mem_size(void);
 phys_addr_t memblock_reserved_size(void);
+unsigned long memblock_estimated_nr_pages(void);
 phys_addr_t memblock_start_of_DRAM(void);
 phys_addr_t memblock_end_of_DRAM(void);
 void memblock_enforce_memory_limit(phys_addr_t memory_limit);
diff --git a/mm/memblock.c b/mm/memblock.c
index e81fb68f7f88..c1f1aac0459f 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1729,6 +1729,25 @@ phys_addr_t __init_memblock memblock_reserved_size(void)
 	return memblock.reserved.total_size;
 }
 
+/**
+ * memblock_estimated_nr_pages - return number of pages from memblock point of
+ * view
+ *
+ * During bootup, system may need number of pages in the whole system to do
+ * some calculation before all pages are freed to buddy system, especially
+ * when CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
+ *
+ * At this point, we can get this information from memblock. Since the system
+ * state is not settle down and address alignment, the value is an estimation.
+ *
+ * Return:
+ * An estimated number of pages from memblock point of view.
+ */
+unsigned long __init memblock_estimated_nr_pages(void)
+{
+	return PHYS_PFN(memblock_phys_mem_size() - memblock_reserved_size());
+}
+
 /* lowest address */
 phys_addr_t __init_memblock memblock_start_of_DRAM(void)
 {
-- 
2.34.1