[PATCH -next] mm, page_alloc: avoid page_to_pfn() in move_freepages()

[Liu Shixin]

From: Kefeng Wang <wangkefeng.w...@huawei.com>

The start_pfn and end_pfn are already available in move_freepages_block(),
there is no need to go back and forth between page and pfn in move_freepages
and move_freepages_block, and pfn_valid_within() should validate pfn first
before touching the page.

Signed-off-by: Kefeng Wang <wangkefeng.w...@huawei.com>
Signed-off-by: Liu Shixin <liushix...@huawei.com>
---
 mm/page_alloc.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c53fe4fa10bf..ccfaa8158862 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2425,19 +2425,21 @@ static inline struct page 
*__rmqueue_cma_fallback(struct zone *zone,
  * boundary. If alignment is required, use move_freepages_block()
  */
 static int move_freepages(struct zone *zone,
-                         struct page *start_page, struct page *end_page,
+                         unsigned long start_pfn, unsigned long end_pfn,
                          int migratetype, int *num_movable)
 {
        struct page *page;
+       unsigned long pfn;
        unsigned int order;
        int pages_moved = 0;
 
-       for (page = start_page; page <= end_page;) {
-               if (!pfn_valid_within(page_to_pfn(page))) {
-                       page++;
+       for (pfn = start_pfn; pfn <= end_pfn;) {
+               if (!pfn_valid_within(pfn)) {
+                       pfn++;
                        continue;
                }
 
+               page = pfn_to_page(pfn);
                if (!PageBuddy(page)) {
                        /*
                         * We assume that pages that could be isolated for
@@ -2447,8 +2449,7 @@ static int move_freepages(struct zone *zone,
                        if (num_movable &&
                                        (PageLRU(page) || __PageMovable(page)))
                                (*num_movable)++;
-
-                       page++;
+                       pfn++;
                        continue;
                }
 
@@ -2458,7 +2459,7 @@ static int move_freepages(struct zone *zone,
 
                order = buddy_order(page);
                move_to_free_list(page, zone, order, migratetype);
-               page += 1 << order;
+               pfn += 1 << order;
                pages_moved += 1 << order;
        }
 
@@ -2468,25 +2469,22 @@ static int move_freepages(struct zone *zone,
 int move_freepages_block(struct zone *zone, struct page *page,
                                int migratetype, int *num_movable)
 {
-       unsigned long start_pfn, end_pfn;
-       struct page *start_page, *end_page;
+       unsigned long start_pfn, end_pfn, pfn;
 
        if (num_movable)
                *num_movable = 0;
 
-       start_pfn = page_to_pfn(page);
-       start_pfn = start_pfn & ~(pageblock_nr_pages-1);
-       start_page = pfn_to_page(start_pfn);
-       end_page = start_page + pageblock_nr_pages - 1;
+       pfn = page_to_pfn(page);
+       start_pfn = pfn & ~(pageblock_nr_pages - 1);
        end_pfn = start_pfn + pageblock_nr_pages - 1;
 
        /* Do not cross zone boundaries */
        if (!zone_spans_pfn(zone, start_pfn))
-               start_page = page;
+               start_pfn = pfn;
        if (!zone_spans_pfn(zone, end_pfn))
                return 0;
 
-       return move_freepages(zone, start_page, end_page, migratetype,
+       return move_freepages(zone, start_pfn, end_pfn, migratetype,
                                                                num_movable);
 }
 
-- 
2.25.1