From 78d6a12dd91a84b0d7e31110b1ea7f4b6a0f8d65 Mon Sep 17 00:00:00 2001
From: Kairui Song <kasong@tencent.com>
Date: Sat, 20 Dec 2025 03:43:40 +0800
Subject: [PATCH] mm, swap: split locked entry duplicating into a standalone
 helper

No feature change, split the common logic into a stand alone helper to be
reused later.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-11-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/swapfile.c | 62 +++++++++++++++++++++++++--------------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ce8c75ede5c31..ced53aba3f4cd 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3667,26 +3667,14 @@ void si_swapinfo(struct sysinfo *val)
  * - swap-cache reference is requested but the entry is not used. -> ENOENT
  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
  */
-static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
+static int swap_dup_entries(struct swap_info_struct *si,
+			    struct swap_cluster_info *ci,
+			    unsigned long offset,
+			    unsigned char usage, int nr)
 {
-	struct swap_info_struct *si;
-	struct swap_cluster_info *ci;
-	unsigned long offset;
-	unsigned char count;
-	unsigned char has_cache;
-	int err, i;
-
-	si = swap_entry_to_info(entry);
-	if (WARN_ON_ONCE(!si)) {
-		pr_err("%s%08lx\n", Bad_file, entry.val);
-		return -EINVAL;
-	}
-
-	offset = swp_offset(entry);
-	VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
-	ci = swap_cluster_lock(si, offset);
+	int i;
+	unsigned char count, has_cache;
 
-	err = 0;
 	for (i = 0; i < nr; i++) {
 		count = si->swap_map[offset + i];
 
@@ -3694,25 +3682,20 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 		 * For swapin out, allocator never allocates bad slots. for
 		 * swapin, readahead is guarded by swap_entry_swapped.
 		 */
-		if (WARN_ON(swap_count(count) == SWAP_MAP_BAD)) {
-			err = -ENOENT;
-			goto unlock_out;
-		}
+		if (WARN_ON(swap_count(count) == SWAP_MAP_BAD))
+			return -ENOENT;
 
 		has_cache = count & SWAP_HAS_CACHE;
 		count &= ~SWAP_HAS_CACHE;
 
 		if (!count && !has_cache) {
-			err = -ENOENT;
+			return -ENOENT;
 		} else if (usage == SWAP_HAS_CACHE) {
 			if (has_cache)
-				err = -EEXIST;
+				return -EEXIST;
 		} else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) {
-			err = -EINVAL;
+			return -EINVAL;
 		}
-
-		if (err)
-			goto unlock_out;
 	}
 
 	for (i = 0; i < nr; i++) {
@@ -3731,14 +3714,31 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 			 * Don't need to rollback changes, because if
 			 * usage == 1, there must be nr == 1.
 			 */
-			err = -ENOMEM;
-			goto unlock_out;
+			return -ENOMEM;
 		}
 
 		WRITE_ONCE(si->swap_map[offset + i], count | has_cache);
 	}
 
-unlock_out:
+	return 0;
+}
+
+static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
+{
+	int err;
+	struct swap_info_struct *si;
+	struct swap_cluster_info *ci;
+	unsigned long offset = swp_offset(entry);
+
+	si = swap_entry_to_info(entry);
+	if (WARN_ON_ONCE(!si)) {
+		pr_err("%s%08lx\n", Bad_file, entry.val);
+		return -EINVAL;
+	}
+
+	VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
+	ci = swap_cluster_lock(si, offset);
+	err = swap_dup_entries(si, ci, offset, usage, nr);
 	swap_cluster_unlock(ci);
 	return err;
 }
-- 
2.47.3