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

From: Barry Song <[email protected]>

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.

Cc "Huang, Ying" <[email protected]>

Cc Chris Li <[email protected]>

Cc Ryan Roberts <[email protected]>

Cc Kairui Song <[email protected]>

Cc David Hildenbrand <[email protected]>

Cc Chuanhua Han <[email protected]>

Signed-off-by Barry Song <[email protected]>

---
 mm/swapfile.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

mm/swapfile.c +5 -10

index f7224bc1320c..c097c513db02 100644
@@ -1352,7 +1352,8 @@ 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 };

@@ -1362,7 +1363,7 @@ 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)) {

@@ -1396,7 +1397,7 @@ 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;
 	}

@@ -3492,15 +3493,9 @@ 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)