linux-kernel - [PATCH v4 2/6] mm: remove the implementation of swap_free() and always use swap_free

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Date: Thu,  9 May 2024 10:40:36 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: baolin.wang@...ux.alibaba.com,
	chrisl@...nel.org,
	david@...hat.com,
	hanchuanhua@...o.com,
	hannes@...xchg.org,
	hughd@...gle.com,
	kasong@...cent.com,
	linux-kernel@...r.kernel.org,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	xiang@...nel.org,
	ying.huang@...el.com,
	yosryahmed@...gle.com,
	yuzhao@...gle.com,
	ziy@...dia.com,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Pavel Machek <pavel@....cz>,
	Len Brown <len.brown@...el.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: [PATCH v4 2/6] mm: remove the implementation of swap_free() and always use swap_free_nr()

From: Barry Song <v-songbaohua@...o.com>

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.

Suggested-by: "Huang, Ying" <ying.huang@...el.com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
Acked-by: Chris Li <chrisl@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Christoph Hellwig <hch@...radead.org>
---
 include/linux/swap.h | 10 +++++-----
 kernel/power/swap.c  |  5 ++---
 mm/swapfile.c        | 17 ++++-------------
 3 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index d1d35e92d7e9..48131b869a4d 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -482,7 +482,6 @@ 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);
@@ -561,10 +560,6 @@ 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)
 {
 }
@@ -613,6 +608,11 @@ 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 5bc04bfe2db1..75bc9e3f9d59 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 ec12f2b9d229..99e701620562 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;
-- 
2.34.1