driver core: Allow device_move(dev, NULL).

If we allow NULL as the new parent in device_move(), we need to make sure
that the device is placed into the same place as it would if it was
newly registered:

- Consider the device virtual tree. In order to be able to reuse code,
  setup_parent() has been tweaked a bit.
- kobject_move() can fall back to the kset's kobject.
- sysfs_move_dir() uses the sysfs root dir as fallback.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 4 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 511edef..2bab1b4 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -378,12 +378,10 @@ int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent)
 	struct sysfs_dirent *new_parent_sd, *sd;
 	int error;
 
-	if (!new_parent)
-		return -EINVAL;
-
 	old_parent_dentry = kobj->parent ?
 		kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
-	new_parent_dentry = new_parent->dentry;
+	new_parent_dentry = new_parent ?
+		new_parent->dentry : sysfs_mount->mnt_sb->s_root;
 
 again:
 	mutex_lock(&old_parent_dentry->d_inode->i_mutex);