[PATCH v3 5/8] mm: swap: drop last SWAP_MAP_SHMEM flag in batch in swap_entries_put_nr()

[Kemeng Shi <shikemeng@huaweicloud.com>]

The SWAP_MAP_SHMEM indicates last map from shmem. Therefore we can drop
SWAP_MAP_SHMEM in batch in similar way to drop last ref count in batch.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 mm/swapfile.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index e83519fbd40e..6f11619665e8 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -192,7 +192,7 @@ static bool swap_is_last_map(struct swap_info_struct *si,
 	unsigned char *map_end = map + nr_pages;
 	unsigned char count = *map;
 
-	if (swap_count(count) != 1)
+	if (swap_count(count) != 1 && swap_count(count) != SWAP_MAP_SHMEM)
 		return false;
 
 	while (++map < map_end) {
@@ -1479,7 +1479,10 @@ static bool swap_entries_put_nr(struct swap_info_struct *si,
 	unsigned char count;
 	int i;
 
-	if (nr <= 1 || swap_count(data_race(si->swap_map[offset])) != 1)
+	if (nr <= 1)
+		goto fallback;
+	count = swap_count(data_race(si->swap_map[offset]));
+	if (count != 1 && count != SWAP_MAP_SHMEM)
 		goto fallback;
 	/* cross into another cluster */
 	if (nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER)
-- 
2.30.0