[PATCH RFC 03/15] mm, swap: move conflict checking logic of out swap cache adding

[Kairui Song via B4 Relay <devnull+kasong.tencent.com@kernel.org>]

From: Kairui Song <kasong@tencent.com>

No feature change, make later commits easier to review.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 mm/swap_state.c | 55 ++++++++++++++++++++++++++++++-------------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 53fa95059012..1e340faea9ac 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -137,6 +137,28 @@ void *swap_cache_get_shadow(swp_entry_t entry)
 	return NULL;
 }
 
+static int __swap_cache_add_check(struct swap_cluster_info *ci,
+				  unsigned int ci_off, unsigned int nr,
+				  void **shadow)
+{
+	unsigned int ci_end = ci_off + nr;
+	unsigned long old_tb;
+
+	if (unlikely(!ci->table))
+		return -ENOENT;
+	do {
+		old_tb = __swap_table_get(ci, ci_off);
+		if (unlikely(swp_tb_is_folio(old_tb)))
+			return -EEXIST;
+		if (unlikely(!__swp_tb_get_count(old_tb)))
+			return -ENOENT;
+		if (swp_tb_is_shadow(old_tb))
+			*shadow = swp_tb_to_shadow(old_tb);
+	} while (++ci_off < ci_end);
+
+	return 0;
+}
+
 void __swap_cache_add_folio(struct swap_cluster_info *ci,
 			    struct folio *folio, swp_entry_t entry)
 {
@@ -179,43 +201,26 @@ static int swap_cache_add_folio(struct folio *folio, swp_entry_t entry,
 {
 	int err;
 	void *shadow = NULL;
-	unsigned long old_tb;
+	unsigned int ci_off;
 	struct swap_info_struct *si;
 	struct swap_cluster_info *ci;
-	unsigned int ci_start, ci_off, ci_end;
 	unsigned long nr_pages = folio_nr_pages(folio);
 
 	si = __swap_entry_to_info(entry);
-	ci_start = swp_cluster_offset(entry);
-	ci_end = ci_start + nr_pages;
-	ci_off = ci_start;
 	ci = swap_cluster_lock(si, swp_offset(entry));
-	if (unlikely(!ci->table)) {
-		err = -ENOENT;
-		goto failed;
+	ci_off = swp_cluster_offset(entry);
+	err = __swap_cache_add_check(ci, ci_off, nr_pages, &shadow);
+	if (err) {
+		swap_cluster_unlock(ci);
+		return err;
 	}
-	do {
-		old_tb = __swap_table_get(ci, ci_off);
-		if (unlikely(swp_tb_is_folio(old_tb))) {
-			err = -EEXIST;
-			goto failed;
-		}
-		if (unlikely(!__swp_tb_get_count(old_tb))) {
-			err = -ENOENT;
-			goto failed;
-		}
-		if (swp_tb_is_shadow(old_tb))
-			shadow = swp_tb_to_shadow(old_tb);
-	} while (++ci_off < ci_end);
+
 	__swap_cache_add_folio(ci, folio, entry);
 	swap_cluster_unlock(ci);
 	if (shadowp)
 		*shadowp = shadow;
-	return 0;
 
-failed:
-	swap_cluster_unlock(ci);
-	return err;
+	return 0;
 }
 
 /**

-- 
2.53.0