[patch 027/135] mm/swapfile.c: clear si->swap_map[] in swap_free_cluster()

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From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm/swapfile.c: clear si->swap_map[] in swap_free_cluster()

si->swap_map[] of the swap entries in cluster needs to be cleared during
freeing.  Previously, this is done in the caller of swap_free_cluster(). 
This may cause code duplication (one user now, will add more users later)
and lock/unlock cluster unnecessarily.  In this patch, the clearing code
is moved to swap_free_cluster() to avoid the downside.

Link: http://lkml.kernel.org/r/20180827075535.17406-4-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: 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>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/swapfile.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/mm/swapfile.c~swap-clear-si-swap_map-in-swap_free_cluster
+++ a/mm/swapfile.c
@@ -932,6 +932,7 @@ static void swap_free_cluster(struct swa
 	struct swap_cluster_info *ci;
 
 	ci = lock_cluster(si, offset);
+	memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
 	cluster_set_count_flag(ci, 0, 0);
 	free_cluster(si, idx);
 	unlock_cluster(ci);
@@ -1250,9 +1251,6 @@ void put_swap_page(struct page *page, sw
 		if (free_entries == SWAPFILE_CLUSTER) {
 			unlock_cluster_or_swap_info(si, ci);
 			spin_lock(&si->lock);
-			ci = lock_cluster(si, offset);
-			memset(map, 0, SWAPFILE_CLUSTER);
-			unlock_cluster(ci);
 			mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
 			swap_free_cluster(si, idx);
 			spin_unlock(&si->lock);
_



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