[PATCH v7 3/5] mm/memblock: introduce memblock_search_pfn_regions()

[Jia He <hejianet@gmail.com>]

This api is to find the memory region index of input pfn. With this
helper, we can improve the loop in early_pfn_valid by recording last
region index. If current pfn and last pfn are in the same memory
region, we needn't do the unnecessary binary searches because the
result of memblock_is_nomap is the same for whole memory region.

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 include/linux/memblock.h | 2 ++
 mm/memblock.c            | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 0257aee..a0127b3 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -203,6 +203,8 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
 	     i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid))
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
+int memblock_search_pfn_regions(unsigned long pfn);
+
 /**
  * for_each_free_mem_range - iterate through free memblock areas
  * @i: u64 used as loop variable
diff --git a/mm/memblock.c b/mm/memblock.c
index ba7c878..0f4004c 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1617,6 +1617,15 @@ static int __init_memblock memblock_search(struct memblock_type *type, phys_addr
 	return -1;
 }
 
+/* search memblock with the input pfn, return the region idx */
+int __init_memblock memblock_search_pfn_regions(unsigned long pfn)
+{
+	struct memblock_type *type = &memblock.memory;
+	int mid = memblock_search(type, PFN_PHYS(pfn));
+
+	return mid;
+}
+
 bool __init memblock_is_reserved(phys_addr_t addr)
 {
 	return memblock_search(&memblock.reserved, addr) != -1;
-- 
2.7.4