[PATCH v4 3/8] swap: Use swap_count() in swap_page_trans_huge_swapped()

[Huang Ying]

In swap_page_trans_huge_swapped(), to identify whether there's any
page table mapping for a 4k sized swap entry, "si->swap_map[i] !=
SWAP_HAS_CACHE" is used.  This works correctly now, because all users
of the function will only call it after checking SWAP_HAS_CACHE.  But
as pointed out by Daniel, it is better to use "swap_count(map[i])"
here, because it works for "map[i] == 0" case too.

And this makes the implementation more consistent between normal and
huge swap entry.

Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Suggested-and-reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 mm/swapfile.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7283104bfafa..833613e59ef7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1497,12 +1497,12 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
 
 	ci = lock_cluster_or_swap_info(si, offset);
 	if (!ci || !cluster_is_huge(ci)) {
-		if (map[roffset] != SWAP_HAS_CACHE)
+		if (swap_count(map[roffset]))
 			ret = true;
 		goto unlock_out;
 	}
 	for (i = 0; i < SWAPFILE_CLUSTER; i++) {
-		if (map[offset + i] != SWAP_HAS_CACHE) {
+		if (swap_count(map[offset + i])) {
 			ret = true;
 			break;
 		}
-- 
2.16.4