linux-kernel - [PATCH v2 11/19] mm, swap: split locked entry duplicating into a standalone helper

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Message-Id: <20251117-swap-table-p2-v2-11-37730e6ea6d5@tencent.com>
Date: Mon, 17 Nov 2025 02:11:52 +0800
From: Kairui Song <ryncsn@...il.com>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>, 
 Barry Song <baohua@...nel.org>, Chris Li <chrisl@...nel.org>, 
 Nhat Pham <nphamcs@...il.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>, 
 David Hildenbrand <david@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
 Youngjun Park <youngjun.park@....com>, Hugh Dickins <hughd@...gle.com>, 
 Baolin Wang <baolin.wang@...ux.alibaba.com>, 
 Ying Huang <ying.huang@...ux.alibaba.com>, 
 Kemeng Shi <shikemeng@...weicloud.com>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
 "Matthew Wilcox (Oracle)" <willy@...radead.org>, 
 linux-kernel@...r.kernel.org, Kairui Song <kasong@...cent.com>
Subject: [PATCH v2 11/19] mm, swap: split locked entry duplicating into a
 standalone helper

From: Kairui Song <kasong@...cent.com>

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

Signed-off-by: Kairui Song <kasong@...cent.com>
---
 mm/swapfile.c | 62 +++++++++++++++++++++++++++++------------------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index d57e83a4d0a7..94d21b755c0c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3654,26 +3654,14 @@ 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];
 
@@ -3681,25 +3669,20 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 		 * Allocator never allocates bad slots, and 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++) {
@@ -3718,14 +3701,31 @@ 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;
 }

-- 
2.51.2