mm: extend 'usage' parameter so that cluster_swap_free_nr() can be reused

Extend a usage parameter so that cluster_swap_free_nr() can be reused by
both swapcache_clear() and swap_free().  __swap_entry_free() is quite
similar but more tricky as it requires the return value of
__swap_entry_free_locked() which cluster_swap_free_nr() doesn't support.

Link: https://lkml.kernel.org/r/20240724020056.65838-1-21cnbao@gmail.comSigned-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Chuanhua Han <hanchuanhua@oppo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swapfile.c

@@ -1344,7 +1344,8 @@ static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
 }
 
 static void cluster_swap_free_nr(struct swap_info_struct *sis,
-		unsigned long offset, int nr_pages)
+		unsigned long offset, int nr_pages,
+		unsigned char usage)
 {
 	struct swap_cluster_info *ci;
 	DECLARE_BITMAP(to_free, BITS_PER_LONG) = { 0 };
@@ -1354,7 +1355,7 @@ static void cluster_swap_free_nr(struct swap_info_struct *sis,
 	while (nr_pages) {
 		nr = min(BITS_PER_LONG, nr_pages);
 		for (i = 0; i < nr; i++) {
-			if (!__swap_entry_free_locked(sis, offset + i, 1))
+			if (!__swap_entry_free_locked(sis, offset + i, usage))
 				bitmap_set(to_free, i, 1);
 		}
 		if (!bitmap_empty(to_free, BITS_PER_LONG)) {
@@ -1388,7 +1389,7 @@ void swap_free_nr(swp_entry_t entry, int nr_pages)
 
 	while (nr_pages) {
 		nr = min_t(int, nr_pages, SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
-		cluster_swap_free_nr(sis, offset, nr);
+		cluster_swap_free_nr(sis, offset, nr, 1);
 		offset += nr;
 		nr_pages -= nr;
 	}
@@ -3472,15 +3473,9 @@ int swapcache_prepare(swp_entry_t entry)
 
 void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
 {
-	struct swap_cluster_info *ci;
 	unsigned long offset = swp_offset(entry);
-	unsigned char usage;
 
-	ci = lock_cluster_or_swap_info(si, offset);
-	usage = __swap_entry_free_locked(si, offset, SWAP_HAS_CACHE);
-	unlock_cluster_or_swap_info(si, ci);
-	if (!usage)
-		free_swap_slot(entry);
+	cluster_swap_free_nr(si, offset, 1, SWAP_HAS_CACHE);
 }
 
 struct swap_info_struct *swp_swap_info(swp_entry_t entry)