debugfs: split the beginning and the end of __create_file() off

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/debugfs/inode.c

@@ -305,11 +305,9 @@ static struct file_system_type debug_fs_type = {
 };
 MODULE_ALIAS_FS("debugfs");
 
-static struct dentry *__create_file(const char *name, umode_t mode,
-				    struct dentry *parent, void *data,
-				    const struct file_operations *fops)
+static struct dentry *start_creating(const char *name, struct dentry *parent)
 {
-	struct dentry *dentry = NULL;
+	struct dentry *dentry;
 	int error;
 
 	pr_debug("debugfs: creating file '%s'\n",name);
@@ -317,7 +315,7 @@ static struct dentry *__create_file(const char *name, umode_t mode,
 	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 			      &debugfs_mount_count);
 	if (error)
-		goto exit;
+		return ERR_PTR(error);
 
 	/* If the parent is not specified, we create it in the root.
 	 * We need the root dentry to do this, which is in the super
@@ -329,11 +327,40 @@ static struct dentry *__create_file(const char *name, umode_t mode,
 
 	mutex_lock(&parent->d_inode->i_mutex);
 	dentry = lookup_one_len(name, parent, strlen(name));
-	if (!IS_ERR(dentry)) {
+	if (!IS_ERR(dentry) && dentry->d_inode) {
+		dput(dentry);
+		dentry = ERR_PTR(-EEXIST);
+	}
+	if (IS_ERR(dentry))
+		mutex_unlock(&parent->d_inode->i_mutex);
+	return dentry;
+}
+
+static struct dentry *end_creating(struct dentry *dentry, int error)
+{
+	mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
+	dput(dentry);
+
+	if (error) {
+		dentry = NULL;
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	}
+	return dentry;
+}
+
+static struct dentry *__create_file(const char *name, umode_t mode,
+				    struct dentry *parent, void *data,
+				    const struct file_operations *fops)
+{
+	struct dentry *dentry = start_creating(name, parent);
+	int error;
+
+	if (IS_ERR(dentry))
+		return NULL;
+
 	switch (mode & S_IFMT) {
 	case S_IFDIR:
 		error = debugfs_mkdir(dentry, mode);
-
 		break;
 	case S_IFLNK:
 		error = debugfs_link(dentry, mode, data);
@@ -342,17 +369,7 @@ static struct dentry *__create_file(const char *name, umode_t mode,
 		error = debugfs_create(dentry, mode, data, fops);
 		break;
 	}
-		dput(dentry);
-	} else
-		error = PTR_ERR(dentry);
-	mutex_unlock(&parent->d_inode->i_mutex);
-
-	if (error) {
-		dentry = NULL;
-		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
-	}
-exit:
-	return dentry;
+	return end_creating(dentry, error);
 }
 
 /**