sysfs: Rewrite rename in terms of sysfs dirents

This patch rewrites sysfs_rename_dir to perform it's checks
as much as possible on the underlying sysfs_dirents instead
of the contents of the dcache.  It turns out that this version
is a little simpler, and a little more like the rest of
the sysfs directory modification code.

tj: fixed double locking of sysfs_mutex

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/sysfs/dir.c

@@ -770,7 +770,7 @@ void sysfs_remove_dir(struct kobject * kobj)
 
 int sysfs_rename_dir(struct kobject * kobj, const char *new_name)
 {
-	struct sysfs_dirent *sd;
+	struct sysfs_dirent *sd = kobj->sd;
 	struct dentry *parent = NULL;
 	struct dentry *old_dentry = NULL, *new_dentry = NULL;
 	const char *dup_name = NULL;
@@ -778,63 +778,57 @@ int sysfs_rename_dir(struct kobject * kobj, const char *new_name)
 
 	mutex_lock(&sysfs_rename_mutex);
 
+	error = 0;
+	if (strcmp(sd->s_name, new_name) == 0)
+		goto out;	/* nothing to rename */
+
 	/* get the original dentry */
-	sd = kobj->sd;
 	old_dentry = sysfs_get_dentry(sd);
 	if (IS_ERR(old_dentry)) {
 		error = PTR_ERR(old_dentry);
-		goto out_dput;
+		goto out;
 	}
 
 	parent = old_dentry->d_parent;
 
 	/* lock parent and get dentry for new name */
 	mutex_lock(&parent->d_inode->i_mutex);
+	mutex_lock(&sysfs_mutex);
 
-	new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
-	if (IS_ERR(new_dentry)) {
-		error = PTR_ERR(new_dentry);
-		goto out_unlock;
-	}
-
-	error = -EINVAL;
-	if (old_dentry == new_dentry)
+	error = -EEXIST;
+	if (sysfs_find_dirent(sd->s_parent, new_name))
 		goto out_unlock;
 
-	error = -EEXIST;
-	if (new_dentry->d_inode)
+	error = -ENOMEM;
+	new_dentry = d_alloc_name(parent, new_name);
+	if (!new_dentry)
 		goto out_unlock;
 
 	/* rename kobject and sysfs_dirent */
 	error = -ENOMEM;
 	new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
 	if (!new_name)
-		goto out_drop;
+		goto out_unlock;
 
 	error = kobject_set_name(kobj, "%s", new_name);
 	if (error)
-		goto out_drop;
+		goto out_unlock;
 
-	mutex_lock(&sysfs_mutex);
 	dup_name = sd->s_name;
 	sd->s_name = new_name;
-	mutex_unlock(&sysfs_mutex);
 
 	/* rename */
 	d_add(new_dentry, NULL);
 	d_move(old_dentry, new_dentry);
 
 	error = 0;
-	goto out_unlock;
-
- out_drop:
-	d_drop(new_dentry);
  out_unlock:
+	mutex_unlock(&sysfs_mutex);
 	mutex_unlock(&parent->d_inode->i_mutex);
- out_dput:
 	kfree(dup_name);
 	dput(old_dentry);
 	dput(new_dentry);
+ out:
 	mutex_unlock(&sysfs_rename_mutex);
 	return error;
 }