[PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

[Zhen Lei]

1. Replace "PAGE_SHIFT - 9" with SECTORS_PER_PAGE_SHIFT

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
 mm/page_io.c  |  4 ++--
 mm/swapfile.c | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index b1d4f4558e6b..51f25238fd9a 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -38,7 +38,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 
 		bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
 		bio_set_dev(bio, bdev);
-		bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
+		bio->bi_iter.bi_sector <<= SECTORS_PER_PAGE_SHIFT;
 		bio->bi_end_io = end_io;
 
 		bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
@@ -266,7 +266,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 
 static sector_t swap_page_sector(struct page *page)
 {
-	return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
+	return (sector_t)__page_file_index(page) << SECTORS_PER_PAGE_SHIFT;
 }
 
 static inline void count_swpout_vm_event(struct page *page)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5871a2aa86a5..0871023c0166 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
 
 	/* Do not discard the swap header page! */
 	se = first_se(si);
-	start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
-	nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
+	start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
+	nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;
 	if (nr_blocks) {
 		err = blkdev_issue_discard(si->bdev, start_block,
 				nr_blocks, GFP_KERNEL, 0);
@@ -188,8 +188,8 @@ static int discard_swap(struct swap_info_struct *si)
 	}
 
 	for (se = next_se(se); se; se = next_se(se)) {
-		start_block = se->start_block << (PAGE_SHIFT - 9);
-		nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
+		start_block = se->start_block << SECTORS_PER_PAGE_SHIFT;
+		nr_blocks = (sector_t)se->nr_pages << SECTORS_PER_PAGE_SHIFT;
 
 		err = blkdev_issue_discard(si->bdev, start_block,
 				nr_blocks, GFP_KERNEL, 0);
@@ -240,8 +240,8 @@ static void discard_swap_cluster(struct swap_info_struct *si,
 		start_page += nr_blocks;
 		nr_pages -= nr_blocks;
 
-		start_block <<= PAGE_SHIFT - 9;
-		nr_blocks <<= PAGE_SHIFT - 9;
+		start_block <<= SECTORS_PER_PAGE_SHIFT;
+		nr_blocks <<= SECTORS_PER_PAGE_SHIFT;
 		if (blkdev_issue_discard(si->bdev, start_block,
 					nr_blocks, GFP_NOIO, 0))
 			break;
-- 
2.26.0.106.g9fadedd