linux-kernel - [PATCH 7/9] mm: swap: free each cluster individually in swap_entries_put_map

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Message-Id: <20250313210515.9920-8-shikemeng@huaweicloud.com>
Date: Fri, 14 Mar 2025 05:05:13 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: akpm@...ux-foundation.org
Cc: kasong@...cent.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 7/9] mm: swap: free each cluster individually in swap_entries_put_map_nr()

1. Factor out general swap_entries_put_map() helper to drop entries belong
to one cluster. If entries are last map, free entries in batch, otherwise
put entries with cluster lock acquired and released only once.
2. Iterate and call swap_entries_put_map() for each cluster in
swap_entries_put_nr() to leverage batch-remove for last map belong to one
cluster and reduce lock acquire/release in fallback case.
3. As swap_entries_put_nr() won't handle SWAP_HSA_CACHE drop, rename it to
swap_entries_put_map_nr().

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 mm/swapfile.c | 58 +++++++++++++++++++++++++--------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2d0f5d630211..ebac9ff74ba7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1473,25 +1473,10 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)
 	return NULL;
 }
 
-static unsigned char swap_entry_put(struct swap_info_struct *si,
-				    swp_entry_t entry)
+static bool swap_entries_put_map(struct swap_info_struct *si,
+				 swp_entry_t entry, int nr)
 {
-	struct swap_cluster_info *ci;
 	unsigned long offset = swp_offset(entry);
-	unsigned char usage;
-
-	ci = lock_cluster(si, offset);
-	usage = swap_entry_put_locked(si, ci, entry, 1);
-	unlock_cluster(ci);
-
-	return usage;
-}
-
-static bool swap_entries_put_nr(struct swap_info_struct *si,
-				swp_entry_t entry, int nr)
-{
-	unsigned long offset = swp_offset(entry);
-	unsigned int type = swp_type(entry);
 	struct swap_cluster_info *ci;
 	bool has_cache = false;
 	unsigned char count;
@@ -1502,9 +1487,6 @@ static bool swap_entries_put_nr(struct swap_info_struct *si,
 	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)
-		goto fallback;
 
 	ci = lock_cluster(si, offset);
 	if (!swap_is_last_map(si, offset, nr, &has_cache)) {
@@ -1521,15 +1503,33 @@ static bool swap_entries_put_nr(struct swap_info_struct *si,
 	return has_cache;
 
 fallback:
-	for (i = 0; i < nr; i++) {
-		if (data_race(si->swap_map[offset + i])) {
-			count = swap_entry_put(si, swp_entry(type, offset + i));
-			if (count == SWAP_HAS_CACHE)
-				has_cache = true;
-		} else {
-			WARN_ON_ONCE(1);
-		}
+	ci = lock_cluster(si, offset);
+	for (i = 0; i < nr; i++, entry.val++) {
+		count = swap_entry_put_locked(si, ci, entry, 1);
+		if (count == SWAP_HAS_CACHE)
+			has_cache = true;
 	}
+	unlock_cluster(ci);
+	return has_cache;
+
+}
+
+static bool swap_entries_put_map_nr(struct swap_info_struct *si,
+				    swp_entry_t entry, int nr)
+{
+	int cluster_nr, cluster_rest;
+	unsigned long offset = swp_offset(entry);
+	bool has_cache = false;
+
+	cluster_rest = SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER;
+	while (nr) {
+		cluster_nr = min(nr, cluster_rest);
+		has_cache |= swap_entries_put_map(si, entry, cluster_nr);
+		cluster_rest = SWAPFILE_CLUSTER;
+		nr -= cluster_nr;
+		entry.val += cluster_nr;
+	}
+
 	return has_cache;
 }
 
@@ -1807,7 +1807,7 @@ void free_swap_and_cache_nr(swp_entry_t entry, int nr)
 	/*
 	 * First free all entries in the range.
 	 */
-	any_only_cache = swap_entries_put_nr(si, entry, nr);
+	any_only_cache = swap_entries_put_map_nr(si, entry, nr);
 
 	/*
 	 * Short-circuit the below loop if none of the entries had their
-- 
2.30.0