[PATCH v4 1/2] mm/sparse.c: Use kvmalloc/kvfree to alloc/free memmap for the classic sparse

[Baoquan He]

This change makes populate_section_memmap()/depopulate_section_memmap
much simpler.

Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
---
v3->v4:
  Split the old v3 into two patches, to carve out the using 'nid'
  as preferred node to allocate memmap into a separate patch. This
  is suggested by Michal, and the carving out is put in patch 2.

v2->v3:
  Remove __GFP_NOWARN and use array_size when calling kvmalloc_node()
  per Matthew's comments.
http://lkml.kernel.org/r/20200312141749.GL27711@MiWiFi-R3L-srv

 mm/sparse.c | 27 +++------------------------
 1 file changed, 3 insertions(+), 24 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index e747a238a860..d01d09cc7d99 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -719,35 +719,14 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 struct page * __meminit populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	struct page *page, *ret;
-	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
-
-	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
-	if (page)
-		goto got_map_page;
-
-	ret = vmalloc(memmap_size);
-	if (ret)
-		goto got_map_ptr;
-
-	return NULL;
-got_map_page:
-	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
-got_map_ptr:
-
-	return ret;
+	return kvmalloc(array_size(sizeof(struct page),
+			PAGES_PER_SECTION), GFP_KERNEL);
 }
 
 static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {
-	struct page *memmap = pfn_to_page(pfn);
-
-	if (is_vmalloc_addr(memmap))
-		vfree(memmap);
-	else
-		free_pages((unsigned long)memmap,
-			   get_order(sizeof(struct page) * PAGES_PER_SECTION));
+	kvfree(pfn_to_page(pfn));
 }
 
 static void free_map_bootmem(struct page *memmap)
-- 
2.17.2