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>

3 files changed, 52 insertions, 36 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 36eedfdeb547..c60114dbe5f5 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -390,22 +390,23 @@ void device_initialize(struct device *dev)
 }
 
 #ifdef CONFIG_SYSFS_DEPRECATED
-static int setup_parent(struct device *dev, struct device *parent)
+static struct kobject * get_device_parent(struct device *dev,
+                                          struct device *parent)
 {
         /* Set the parent to the class, not the parent device */
         /* this keeps sysfs from having a symlink to make old udevs happy */
         if (dev->class)
-                dev->kobj.parent = &dev->class->subsys.kset.kobj;
+                return &dev->class->subsys.kset.kobj;
         else if (parent)
-                dev->kobj.parent = &parent->kobj;
+                return &parent->kobj;
 
-        return 0;
+        return NULL;
 }
 #else
-static int virtual_device_parent(struct device *dev)
+static struct kobject * virtual_device_parent(struct device *dev)
 {
         if (!dev->class)
-                return -ENODEV;
+                return ERR_PTR(-ENODEV);
 
         if (!dev->class->virtual_dir) {
                 static struct kobject *virtual_dir = NULL;
@@ -415,25 +416,31 @@ static int virtual_device_parent(struct device *dev)
                 dev->class->virtual_dir = kobject_add_dir(virtual_dir, dev->class->name);
         }
 
-        dev->kobj.parent = dev->class->virtual_dir;
-        return 0;
+        return dev->class->virtual_dir;
 }
 
-static int setup_parent(struct device *dev, struct device *parent)
+static struct kobject * get_device_parent(struct device *dev,
+                                          struct device *parent)
 {
-        int error;
-
         /* if this is a class device, and has no parent, create one */
         if ((dev->class) && (parent == NULL)) {
-                error = virtual_device_parent(dev);
-                if (error)
-                        return error;
+                return virtual_device_parent(dev);
         } else if (parent)
-                dev->kobj.parent = &parent->kobj;
+                return &parent->kobj;
+        return NULL;
+}
 
+#endif
+static int setup_parent(struct device *dev, struct device *parent)
+{
+        struct kobject *kobj;
+        kobj = get_device_parent(dev, parent);
+        if (IS_ERR(kobj))
+                return PTR_ERR(kobj);
+        if (kobj)
+                dev->kobj.parent = kobj;
         return 0;
 }
-#endif
 
 /**
  *      device_add - add device to device hierarchy.
@@ -976,12 +983,18 @@ static int device_move_class_links(struct device *dev,
                 sysfs_remove_link(&dev->kobj, "device");
                 sysfs_remove_link(&old_parent->kobj, class_name);
         }
-        error = sysfs_create_link(&dev->kobj, &new_parent->kobj, "device");
-        if (error)
-                goto out;
-        error = sysfs_create_link(&new_parent->kobj, &dev->kobj, class_name);
-        if (error)
-                sysfs_remove_link(&dev->kobj, "device");
+        if (new_parent) {
+                error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
+                                          "device");
+                if (error)
+                        goto out;
+                error = sysfs_create_link(&new_parent->kobj, &dev->kobj,
+                                          class_name);
+                if (error)
+                        sysfs_remove_link(&dev->kobj, "device");
+        }
+        else
+                error = 0;
 out:
         kfree(class_name);
         return error;
@@ -993,25 +1006,28 @@ out:
 /**
  * device_move - moves a device to a new parent
  * @dev: the pointer to the struct device to be moved
- * @new_parent: the new parent of the device
+ * @new_parent: the new parent of the device (can by NULL)
  */
 int device_move(struct device *dev, struct device *new_parent)
 {
         int error;
         struct device *old_parent;
+        struct kobject *new_parent_kobj;
 
         dev = get_device(dev);
         if (!dev)
                 return -EINVAL;
 
         new_parent = get_device(new_parent);
-        if (!new_parent) {
-                error = -EINVAL;
+        new_parent_kobj = get_device_parent (dev, new_parent);
+        if (IS_ERR(new_parent_kobj)) {
+                error = PTR_ERR(new_parent_kobj);
+                put_device(new_parent);
                 goto out;
         }
         pr_debug("DEVICE: moving '%s' to '%s'\n", dev->bus_id,
-                new_parent->bus_id);
-        error = kobject_move(&dev->kobj, &new_parent->kobj);
+                 new_parent ? new_parent->bus_id : "<NULL>");
+        error = kobject_move(&dev->kobj, new_parent_kobj);
         if (error) {
                 put_device(new_parent);
                 goto out;
@@ -1020,7 +1036,8 @@ int device_move(struct device *dev, struct device *new_parent)
         dev->parent = new_parent;
         if (old_parent)
                 klist_remove(&dev->knode_parent);
-        klist_add_tail(&dev->knode_parent, &new_parent->klist_children);
+        if (new_parent)
+                klist_add_tail(&dev->knode_parent, &new_parent->klist_children);
         if (!dev->class)
                 goto out_put;
         error = device_move_class_links(dev, old_parent, new_parent);
@@ -1028,7 +1045,8 @@ int device_move(struct device *dev, struct device *new_parent)
                 /* We ignore errors on cleanup since we're hosed anyway... */
                 device_move_class_links(dev, new_parent, old_parent);
                 if (!kobject_move(&dev->kobj, &old_parent->kobj)) {
-                        klist_remove(&dev->knode_parent);
+                        if (new_parent)
+                                klist_remove(&dev->knode_parent);
                         if (old_parent)
                                 klist_add_tail(&dev->knode_parent,
                                                &old_parent->klist_children);
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 511edef8b321..2bab1b4ddf5a 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);
diff --git a/lib/kobject.c b/lib/kobject.c
index 9aed594bfcac..c033dc8fa9af 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -314,7 +314,7 @@ int kobject_rename(struct kobject * kobj, const char *new_name)
 /**
  *      kobject_move - move object to another parent
  *      @kobj:  object in question.
- *      @new_parent: object's new parent
+ *      @new_parent: object's new parent (can be NULL)
  */
 
 int kobject_move(struct kobject *kobj, struct kobject *new_parent)
@@ -330,8 +330,8 @@ int kobject_move(struct kobject *kobj, struct kobject *new_parent)
                 return -EINVAL;
         new_parent = kobject_get(new_parent);
         if (!new_parent) {
-                error = -EINVAL;
-                goto out;
+                if (kobj->kset)
+                        new_parent = kobject_get(&kobj->kset->kobj);
         }
         /* old object path */
         devpath = kobject_get_path(kobj, GFP_KERNEL);