Btrfs: add helper for closing one device

Signed-off-by: NAnand Jain <anand.jain@oracle.com>
[reworded subject and changelog]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -764,36 +764,7 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
-		struct btrfs_device *new_device;
-		struct rcu_string *name;
-
-		if (device->bdev)
-			fs_devices->open_devices--;
-
-		if (device->writeable &&
-		    device->devid != BTRFS_DEV_REPLACE_DEVID) {
-			list_del_init(&device->dev_alloc_list);
-			fs_devices->rw_devices--;
-		}
-
-		if (device->missing)
-			fs_devices->missing_devices--;
-
-		new_device = btrfs_alloc_device(NULL, &device->devid,
-						device->uuid);
-		BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
-
-		/* Safe because we are under uuid_mutex */
-		if (device->name) {
-			name = rcu_string_strdup(device->name->str, GFP_NOFS);
-			BUG_ON(!name); /* -ENOMEM */
-			rcu_assign_pointer(new_device->name, name);
-		}
-
-		list_replace_rcu(&device->dev_list, &new_device->dev_list);
-		new_device->fs_devices = device->fs_devices;
-
-		call_rcu(&device->rcu, free_device);
+		btrfs_close_one_device(device);
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
 
@@ -6834,3 +6805,38 @@ void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info)
 		fs_devices = fs_devices->seed;
 	}
 }
+
+void btrfs_close_one_device(struct btrfs_device *device)
+{
+	struct btrfs_fs_devices *fs_devices = device->fs_devices;
+	struct btrfs_device *new_device;
+	struct rcu_string *name;
+
+	if (device->bdev)
+		fs_devices->open_devices--;
+
+	if (device->writeable &&
+	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
+		list_del_init(&device->dev_alloc_list);
+		fs_devices->rw_devices--;
+	}
+
+	if (device->missing)
+		fs_devices->missing_devices--;
+
+	new_device = btrfs_alloc_device(NULL, &device->devid,
+					device->uuid);
+	BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
+
+	/* Safe because we are under uuid_mutex */
+	if (device->name) {
+		name = rcu_string_strdup(device->name->str, GFP_NOFS);
+		BUG_ON(!name); /* -ENOMEM */
+		rcu_assign_pointer(new_device->name, name);
+	}
+
+	list_replace_rcu(&device->dev_list, &new_device->dev_list);
+	new_device->fs_devices = device->fs_devices;
+
+	call_rcu(&device->rcu, free_device);
+}

fs/btrfs/volumes.h

@@ -547,5 +547,6 @@ static inline void unlock_chunks(struct btrfs_root *root)
 struct list_head *btrfs_get_fs_uuids(void);
 void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info);
 void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info);
+void btrfs_close_one_device(struct btrfs_device *device);
 
 #endif