linux-kernel - [PATCH v2 3/8] mm: swap: use swap_entries_free() to free swap entry in swap_entry_put

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Message-Id: <20250318150614.6415-4-shikemeng@huaweicloud.com>
Date: Tue, 18 Mar 2025 23:06:09 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: akpm@...ux-foundation.org
Cc: tim.c.chen@...ux.intel.com,
	ryncsn@...il.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/8] mm: swap: use swap_entries_free() to free swap entry in swap_entry_put_locked()

In swap_entry_put_locked(), we will set slot to SWAP_HAS_CACHE before
using swap_entries_free() to do actual swap entry freeing. This
introduce an unnecessary intermediate state.
By using swap_entries_free() in swap_entry_put_locked(), we can
eliminate the need to set slot to SWAP_HAS_CACHE.
This change would make the behavior of swap_entry_put_locked() more
consistent with other put() operations which will do actual free work
after put last reference.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 mm/swapfile.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0aa7ce82c013..40e41e514813 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1348,9 +1348,11 @@ static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
 }
 
 static unsigned char swap_entry_put_locked(struct swap_info_struct *si,
-					   unsigned long offset,
+					   struct swap_cluster_info *ci,
+					   swp_entry_t entry,
 					   unsigned char usage)
 {
+	unsigned long offset = swp_offset(entry);
 	unsigned char count;
 	unsigned char has_cache;
 
@@ -1382,7 +1384,7 @@ static unsigned char swap_entry_put_locked(struct swap_info_struct *si,
 	if (usage)
 		WRITE_ONCE(si->swap_map[offset], usage);
 	else
-		WRITE_ONCE(si->swap_map[offset], SWAP_HAS_CACHE);
+		swap_entries_free(si, ci, entry, 1);
 
 	return usage;
 }
@@ -1461,9 +1463,7 @@ static unsigned char swap_entry_put(struct swap_info_struct *si,
 	unsigned char usage;
 
 	ci = lock_cluster(si, offset);
-	usage = swap_entry_put_locked(si, offset, 1);
-	if (!usage)
-		swap_entries_free(si, ci, swp_entry(si->type, offset), 1);
+	usage = swap_entry_put_locked(si, ci, entry, 1);
 	unlock_cluster(ci);
 
 	return usage;
@@ -1551,8 +1551,8 @@ static void cluster_swap_free_nr(struct swap_info_struct *si,
 
 	ci = lock_cluster(si, offset);
 	do {
-		if (!swap_entry_put_locked(si, offset, usage))
-			swap_entries_free(si, ci, swp_entry(si->type, offset), 1);
+		swap_entry_put_locked(si, ci, swp_entry(si->type, offset),
+				      usage);
 	} while (++offset < end);
 	unlock_cluster(ci);
 }
@@ -1596,12 +1596,9 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry)
 	ci = lock_cluster(si, offset);
 	if (swap_only_has_cache(si, offset, size))
 		swap_entries_free(si, ci, entry, size);
-	else {
-		for (int i = 0; i < size; i++, entry.val++) {
-			if (!swap_entry_put_locked(si, offset + i, SWAP_HAS_CACHE))
-				swap_entries_free(si, ci, entry, 1);
-		}
-	}
+	else
+		for (int i = 0; i < size; i++, entry.val++)
+			swap_entry_put_locked(si, ci, entry, SWAP_HAS_CACHE);
 	unlock_cluster(ci);
 }
 
-- 
2.30.0