mm: remove the implementation of swap_free() and always use swap_free_nr()

To streamline maintenance efforts, we propose removing the implementation
of swap_free().  Instead, we can simply invoke swap_free_nr() with nr set
to 1.  swap_free_nr() is designed with a bitmap consisting of only one
long, resulting in overhead that can be ignored for cases where nr equals
1.

A prime candidate for leveraging swap_free_nr() lies within
kernel/power/swap.c.  Implementing this change facilitates the adoption of
batch processing for hibernation.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Barry Song <[email protected]>
Suggested-by: "Huang, Ying" <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
Acked-by: Chris Li <[email protected]>
Reviewed-by: Ryan Roberts <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Andreas Larsson <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Chuanhua Han <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Gao Xiang <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: Khalid Aziz <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Yosry Ahmed <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

3 files changed, 11 insertions, 21 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 0f41fe49c9dc..d33ce740b695 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -477,7 +477,6 @@ extern int add_swap_count_continuation(swp_entry_t, gfp_t);
 extern void swap_shmem_alloc(swp_entry_t);
 extern int swap_duplicate(swp_entry_t);
 extern int swapcache_prepare(swp_entry_t);
-extern void swap_free(swp_entry_t);
 extern void swap_free_nr(swp_entry_t entry, int nr_pages);
 extern void swapcache_free_entries(swp_entry_t *entries, int n);
 extern void free_swap_and_cache_nr(swp_entry_t entry, int nr);
@@ -556,10 +555,6 @@ static inline int swapcache_prepare(swp_entry_t swp)
 	return 0;
 }
 
-static inline void swap_free(swp_entry_t swp)
-{
-}
-
 static inline void swap_free_nr(swp_entry_t entry, int nr_pages)
 {
 }
@@ -608,6 +603,11 @@ static inline void free_swap_and_cache(swp_entry_t entry)
 	free_swap_and_cache_nr(entry, 1);
 }
 
+static inline void swap_free(swp_entry_t entry)
+{
+	swap_free_nr(entry, 1);
+}
+
 #ifdef CONFIG_MEMCG
 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 {
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 753b8dd42a59..82b884b67152 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -200,12 +200,11 @@ void free_all_swap_pages(int swap)
 
 	while ((node = swsusp_extents.rb_node)) {
 		struct swsusp_extent *ext;
-		unsigned long offset;
 
 		ext = rb_entry(node, struct swsusp_extent, node);
 		rb_erase(node, &swsusp_extents);
-		for (offset = ext->start; offset <= ext->end; offset++)
-			swap_free(swp_entry(swap, offset));
+		swap_free_nr(swp_entry(swap, ext->start),
+			     ext->end - ext->start + 1);
 
 		kfree(ext);
 	}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 92a045d34a97..9c6d8e557c0f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1343,19 +1343,6 @@ static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
 	swap_range_free(p, offset, 1);
 }
 
-/*
- * Caller has made sure that the swap device corresponding to entry
- * is still around or has not been recycled.
- */
-void swap_free(swp_entry_t entry)
-{
-	struct swap_info_struct *p;
-
-	p = _swap_info_get(entry);
-	if (p)
-		__swap_entry_free(p, entry);
-}
-
 static void cluster_swap_free_nr(struct swap_info_struct *sis,
 		unsigned long offset, int nr_pages)
 {
@@ -1385,6 +1372,10 @@ static void cluster_swap_free_nr(struct swap_info_struct *sis,
 	unlock_cluster_or_swap_info(sis, ci);
 }
 
+/*
+ * Caller has made sure that the swap device corresponding to entry
+ * is still around or has not been recycled.
+ */
 void swap_free_nr(swp_entry_t entry, int nr_pages)
 {
 	int nr;