[PATCH 2/2] Btrfs: fix wrong total device counter after removing a seed device

[Miao Xie <miaox@cn.fujitsu.com>]

The total device counters of all the descendant filesystem account the seed
device, so after removing a seed device, we need decrease all those counters.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/volumes.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4cfbe76..184e1c4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1715,12 +1715,16 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 	 * (super_copy) should hold the device list mutex.
 	 */
 
-	cur_devices = device->fs_devices;
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
 	list_del_rcu(&device->dev_list);
 
 	device->fs_devices->num_devices--;
-	device->fs_devices->total_devices--;
+
+	cur_devices = root->fs_info->fs_devices;
+	do {
+		cur_devices->total_devices--;
+		cur_devices = cur_devices->seed;
+	} while (device->fs_devices != cur_devices);
 
 	if (device->missing)
 		device->fs_devices->missing_devices--;
@@ -1738,12 +1742,12 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 	/* remove sysfs entry */
 	btrfs_kobj_rm_device(root->fs_info, device);
 
-	call_rcu(&device->rcu, free_device);
-
 	num_devices = btrfs_super_num_devices(root->fs_info->super_copy) - 1;
 	btrfs_set_super_num_devices(root->fs_info->super_copy, num_devices);
 	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
+	call_rcu(&device->rcu, free_device);
+
 	if (cur_devices->open_devices == 0) {
 		struct btrfs_fs_devices *fs_devices;
 		fs_devices = root->fs_info->fs_devices;
-- 
1.9.3