[PATCH v2 1/2] mm/swapfile: Extract operations of resource release in the swapoff process

[liubo]

In order to realize the interface reuse in the swapoff resource
release process, some of the operations are abstracted
into separate interfaces.

Only code movement, no functional modifications and changes.

del_useless_swap_info():
Remove specific swap_info_struct from swap_active_head and
update total_swap_pages.

release_swap_info_memory():
Clear the corresponding resources of swap_info_struct.

Signed-off-by: liubo <liubo254@xxxxxxxxxx>
---
v2:
Only code movement, no functional modifications and changes.
Former: https://lore.kernel.org/linux-mm/20220528084941.28391-1-liubo254@xxxxxxxxxx/
---
 mm/swapfile.c | 168 +++++++++++++++++++++++++++-----------------------
 1 file changed, 91 insertions(+), 77 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3fa26f6971e9..2ef5e7b4918e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2386,18 +2386,103 @@ bool has_usable_swap(void)
 	return ret;
 }
 
-SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
+static void release_swap_info_memory(struct swap_info_struct *p)
 {
-	struct swap_info_struct *p = NULL;
 	unsigned char *swap_map;
 	struct swap_cluster_info *cluster_info;
 	unsigned long *frontswap_map;
-	struct file *swap_file, *victim;
+	struct file *swap_file;
 	struct address_space *mapping;
 	struct inode *inode;
+	unsigned int old_block_size;
+
+	mutex_lock(&swapon_mutex);
+	spin_lock(&swap_lock);
+	spin_lock(&p->lock);
+	drain_mmlist();
+
+	/* wait for anyone still in scan_swap_map */
+	p->highest_bit = 0;		/* cuts scans short */
+	while (p->flags >= SWP_SCANNING) {
+		spin_unlock(&p->lock);
+		spin_unlock(&swap_lock);
+		schedule_timeout_uninterruptible(1);
+		spin_lock(&swap_lock);
+		spin_lock(&p->lock);
+	}
+
+	swap_file = p->swap_file;
+	mapping = p->swap_file->f_mapping;
+	old_block_size = p->old_block_size;
+	p->swap_file = NULL;
+	p->max = 0;
+	swap_map = p->swap_map;
+	p->swap_map = NULL;
+	cluster_info = p->cluster_info;
+	p->cluster_info = NULL;
+	frontswap_map = frontswap_map_get(p);
+	spin_unlock(&p->lock);
+	spin_unlock(&swap_lock);
+	arch_swap_invalidate_area(p->type);
+	frontswap_invalidate_area(p->type);
+	frontswap_map_set(p, NULL);
+	mutex_unlock(&swapon_mutex);
+	free_percpu(p->percpu_cluster);
+	p->percpu_cluster = NULL;
+	free_percpu(p->cluster_next_cpu);
+	p->cluster_next_cpu = NULL;
+	vfree(swap_map);
+	kvfree(cluster_info);
+	kvfree(frontswap_map);
+	/* Destroy swap account information */
+	swap_cgroup_swapoff(p->type);
+	exit_swap_address_space(p->type);
+
+	inode = mapping->host;
+	if (S_ISBLK(inode->i_mode)) {
+		struct block_device *bdev = I_BDEV(inode);
+
+		set_blocksize(bdev, old_block_size);
+		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+	}
+
+	inode_lock(inode);
+	inode->i_flags &= ~S_SWAPFILE;
+	inode_unlock(inode);
+	filp_close(swap_file, NULL);
+}
+
+static void del_useless_swap_info(struct swap_info_struct *p)
+{
+	del_from_avail_list(p);
+	spin_lock(&p->lock);
+	if (p->prio < 0) {
+		struct swap_info_struct *si = p;
+		int nid;
+
+		plist_for_each_entry_continue(si, &swap_active_head, list) {
+			si->prio++;
+			si->list.prio--;
+			for_each_node(nid) {
+				if (si->avail_lists[nid].prio != 1)
+					si->avail_lists[nid].prio--;
+			}
+		}
+		least_priority++;
+	}
+	plist_del(&p->list, &swap_active_head);
+	atomic_long_sub(p->pages, &nr_swap_pages);
+	p->flags &= ~SWP_WRITEOK;
+	spin_unlock(&p->lock);
+}
+
+SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
+{
+	struct swap_info_struct *p = NULL;
+	struct file *victim;
+	struct address_space *mapping;
 	struct filename *pathname;
 	int err, found = 0;
-	unsigned int old_block_size;
 	unsigned int inuse_pages;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -2440,26 +2525,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 		spin_unlock(&swap_lock);
 		goto out_dput;
 	}
-	del_from_avail_list(p);
-	spin_lock(&p->lock);
-	if (p->prio < 0) {
-		struct swap_info_struct *si = p;
-		int nid;
 
-		plist_for_each_entry_continue(si, &swap_active_head, list) {
-			si->prio++;
-			si->list.prio--;
-			for_each_node(nid) {
-				if (si->avail_lists[nid].prio != 1)
-					si->avail_lists[nid].prio--;
-			}
-		}
-		least_priority++;
-	}
-	plist_del(&p->list, &swap_active_head);
-	atomic_long_sub(p->pages, &nr_swap_pages);
-	p->flags &= ~SWP_WRITEOK;
-	spin_unlock(&p->lock);
+	del_useless_swap_info(p);
 	spin_unlock(&swap_lock);
 
 	disable_swap_slots_cache_lock();
@@ -2497,60 +2564,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	if (!p->bdev || !bdev_nonrot(p->bdev))
 		atomic_dec(&nr_rotate_swap);
 
-	mutex_lock(&swapon_mutex);
-	spin_lock(&swap_lock);
-	spin_lock(&p->lock);
-	drain_mmlist();
-
-	/* wait for anyone still in scan_swap_map_slots */
-	p->highest_bit = 0;		/* cuts scans short */
-	while (p->flags >= SWP_SCANNING) {
-		spin_unlock(&p->lock);
-		spin_unlock(&swap_lock);
-		schedule_timeout_uninterruptible(1);
-		spin_lock(&swap_lock);
-		spin_lock(&p->lock);
-	}
-
-	swap_file = p->swap_file;
-	old_block_size = p->old_block_size;
-	p->swap_file = NULL;
-	p->max = 0;
-	swap_map = p->swap_map;
-	p->swap_map = NULL;
-	cluster_info = p->cluster_info;
-	p->cluster_info = NULL;
-	frontswap_map = frontswap_map_get(p);
-	spin_unlock(&p->lock);
-	spin_unlock(&swap_lock);
-	arch_swap_invalidate_area(p->type);
-	frontswap_invalidate_area(p->type);
-	frontswap_map_set(p, NULL);
-	mutex_unlock(&swapon_mutex);
-	free_percpu(p->percpu_cluster);
-	p->percpu_cluster = NULL;
-	free_percpu(p->cluster_next_cpu);
-	p->cluster_next_cpu = NULL;
-	vfree(swap_map);
-	kvfree(cluster_info);
-	kvfree(frontswap_map);
-	/* Destroy swap account information */
-	swap_cgroup_swapoff(p->type);
-	exit_swap_address_space(p->type);
-
-	inode = mapping->host;
-	if (S_ISBLK(inode->i_mode)) {
-		struct block_device *bdev = I_BDEV(inode);
-
-		set_blocksize(bdev, old_block_size);
-		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
-	}
-
-	inode_lock(inode);
-	inode->i_flags &= ~S_SWAPFILE;
-	inode_unlock(inode);
-	filp_close(swap_file, NULL);
-
+	release_swap_info_memory(p);
 	/*
 	 * Clear the SWP_USED flag after all resources are freed so that swapon
 	 * can reuse this swap_info in alloc_swap_info() safely.  It is ok to
-- 
2.27.0