linux-kernel - [PATCH 3/3] swap: Clear si->swap_map[] in swap_free

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Date:   Mon, 27 Aug 2018 15:55:35 +0800
From:   Huang Ying <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shaohua Li <shli@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>
Subject: [PATCH 3/3] swap: 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.

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Shaohua Li <shli@...nel.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Minchan Kim <minchan@...nel.org>
---
 mm/swapfile.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ef974bbd7715..97a1bd1a7c9a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -933,6 +933,7 @@ static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
 	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);
@@ -1309,9 +1310,6 @@ void put_swap_page(struct page *page, swp_entry_t entry)
 		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);
-- 
2.16.4