mm: swap: clean up initialization helper

At this point, alloc_cluster is never called already, and
inc_cluster_info_page is called by initialization only, a lot of dead code
can be dropped.

Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-4-cb9c148b9297@kernel.orgSigned-off-by: Kairui Song <kasong@tencent.com>
Reported-by: Barry Song <21cnbao@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swapfile.c

@@ -438,20 +438,6 @@ static void swap_users_ref_free(struct percpu_ref *ref)
 	complete(&si->comp);
 }
 
-static struct swap_cluster_info *alloc_cluster(struct swap_info_struct *si, unsigned long idx)
-{
-	struct swap_cluster_info *ci = list_first_entry(&si->free_clusters,
-							struct swap_cluster_info, list);
-
-	lockdep_assert_held(&si->lock);
-	lockdep_assert_held(&ci->lock);
-	VM_BUG_ON(cluster_index(si, ci) != idx);
-	VM_BUG_ON(ci->count);
-	list_del(&ci->list);
-	ci->flags = 0;
-	return ci;
-}
-
 static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci)
 {
 	VM_BUG_ON(ci->count != 0);
@@ -472,34 +458,24 @@ static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *
 }
 
 /*
- * The cluster corresponding to page_nr will be used. The cluster will be
- * removed from free cluster list and its usage counter will be increased by
- * count.
+ * The cluster corresponding to page_nr will be used. The cluster will not be
+ * added to free cluster list and its usage counter will be increased by 1.
+ * Only used for initialization.
  */
-static void add_cluster_info_page(struct swap_info_struct *p,
-	struct swap_cluster_info *cluster_info, unsigned long page_nr,
-	unsigned long count)
+static void inc_cluster_info_page(struct swap_info_struct *p,
+	struct swap_cluster_info *cluster_info, unsigned long page_nr)
 {
 	unsigned long idx = page_nr / SWAPFILE_CLUSTER;
-	struct swap_cluster_info *ci = cluster_info + idx;
+	struct swap_cluster_info *ci;
 
 	if (!cluster_info)
 		return;
-	if (cluster_is_free(ci))
-		alloc_cluster(p, idx);
 
-	VM_BUG_ON(ci->count + count > SWAPFILE_CLUSTER);
-	ci->count += count;
-}
+	ci = cluster_info + idx;
+	ci->count++;
 
-/*
- * The cluster corresponding to page_nr will be used. The cluster will be
- * removed from free cluster list and its usage counter will be increased by 1.
- */
-static void inc_cluster_info_page(struct swap_info_struct *p,
-	struct swap_cluster_info *cluster_info, unsigned long page_nr)
-{
-	add_cluster_info_page(p, cluster_info, page_nr, 1);
+	VM_BUG_ON(ci->count > SWAPFILE_CLUSTER);
+	VM_BUG_ON(ci->flags);
 }
 
 /*