[PATCH v2] mm/mm_init.c: simplify logic of deferred_[init|free]_pages

[Wei Yang <richard.weiyang@xxxxxxxxx>]

Function deferred_[init|free]_pages are only used in
deferred_init_maxorder(), which makes sure the range to init/free is
within MAX_ORDER_NR_PAGES size.

With this knowledge, we can simplify these two functions. Since

  * only the first pfn could be IS_MAX_ORDER_ALIGNED()

Also since the range passed to deferred_[init|free]_pages is always from
memblock.memory for those we have already allocated memmap to cover,
pfn_valid() always return true. Then we can remove related check.

Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
CC: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
CC: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
CC: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>

---
v2: adjust function declaration indention per David's comment
---
 mm/mm_init.c | 64 +++++++---------------------------------------------
 1 file changed, 8 insertions(+), 56 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index c152c60eca3d..42fd0b822ca5 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1911,8 +1911,8 @@ unsigned long __init node_map_pfn_alignment(void)
 }
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
-static void __init deferred_free_range(unsigned long pfn,
-				       unsigned long nr_pages)
+static void __init deferred_free_pages(unsigned long pfn,
+		unsigned long nr_pages)
 {
 	struct page *page;
 	unsigned long i;
@@ -1950,69 +1950,21 @@ static inline void __init pgdat_init_report_one_done(void)
 		complete(&pgdat_init_all_done_comp);
 }
 
-/*
- * Returns true if page needs to be initialized or freed to buddy allocator.
- *
- * We check if a current MAX_PAGE_ORDER block is valid by only checking the
- * validity of the head pfn.
- */
-static inline bool __init deferred_pfn_valid(unsigned long pfn)
-{
-	if (IS_MAX_ORDER_ALIGNED(pfn) && !pfn_valid(pfn))
-		return false;
-	return true;
-}
-
-/*
- * Free pages to buddy allocator. Try to free aligned pages in
- * MAX_ORDER_NR_PAGES sizes.
- */
-static void __init deferred_free_pages(unsigned long pfn,
-				       unsigned long end_pfn)
-{
-	unsigned long nr_free = 0;
-
-	for (; pfn < end_pfn; pfn++) {
-		if (!deferred_pfn_valid(pfn)) {
-			deferred_free_range(pfn - nr_free, nr_free);
-			nr_free = 0;
-		} else if (IS_MAX_ORDER_ALIGNED(pfn)) {
-			deferred_free_range(pfn - nr_free, nr_free);
-			nr_free = 1;
-		} else {
-			nr_free++;
-		}
-	}
-	/* Free the last block of pages to allocator */
-	deferred_free_range(pfn - nr_free, nr_free);
-}
-
 /*
  * Initialize struct pages.  We minimize pfn page lookups and scheduler checks
  * by performing it only once every MAX_ORDER_NR_PAGES.
  * Return number of pages initialized.
  */
-static unsigned long  __init deferred_init_pages(struct zone *zone,
-						 unsigned long pfn,
-						 unsigned long end_pfn)
+static unsigned long __init deferred_init_pages(struct zone *zone,
+		unsigned long pfn, unsigned long end_pfn)
 {
 	int nid = zone_to_nid(zone);
-	unsigned long nr_pages = 0;
+	unsigned long nr_pages = end_pfn - pfn;
 	int zid = zone_idx(zone);
-	struct page *page = NULL;
+	struct page *page = pfn_to_page(pfn);
 
-	for (; pfn < end_pfn; pfn++) {
-		if (!deferred_pfn_valid(pfn)) {
-			page = NULL;
-			continue;
-		} else if (!page || IS_MAX_ORDER_ALIGNED(pfn)) {
-			page = pfn_to_page(pfn);
-		} else {
-			page++;
-		}
+	for (; pfn < end_pfn; pfn++, page++)
 		__init_single_page(page, pfn, zid, nid);
-		nr_pages++;
-	}
 	return nr_pages;
 }
 
@@ -2096,7 +2048,7 @@ deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
 			break;
 
 		t = min(mo_pfn, epfn);
-		deferred_free_pages(spfn, t);
+		deferred_free_pages(spfn, t - spfn);
 
 		if (mo_pfn <= epfn)
 			break;
-- 
2.34.1