Here are five possible code completions for the given function:

**1. Simple Error Handling**
```c
static void ffs_user_copy_worker(struct work_struct *work)
{
    struct ffs_io_data *io_data = container_of(work, struct ffs_io_data, work);
    int ret = io_data->status;

    if (ret != 0) {
        printk(KERN_ERR "ffs_user_copy_worker: error %d\n", ret);
    }
}
```

**2. Freeing Memory**
```c
static void ffs_user_copy_worker(struct work_struct *work)
{
    struct ffs_io_data *io_data = container_of(work, struct ffs_io_data, work);
    int ret = io_data->status;

    if (ret != 0) {
        printk(KERN_ERR "ffs_user_copy_worker: error %d\n", ret);
    }
    kfree(io_data);
}
```

**3. Notifying Completion**
```c
static void ffs_user_copy_worker(struct work_struct *work)
{
    struct ffs_io_data *io_data = container_of(work, struct ffs_io_data, work);
    int ret = io_data->status;

    if (ret != 0) {
        printk(KERN_ERR "ffs_user_copy_worker: error %d\n", ret);
    }
    complete(&io_data->completion);
}
```

**4. Waking Up Waiters**
```c
static void ffs_user_copy_worker(struct work_struct *work)
{
    struct ffs_io_data *io_data = container_of(work, struct ffs_io_data, work);
    int ret = io_data->status;

    if (ret != 0) {
        printk(KERN_ERR "ffs_user_copy_worker: error %d\n", ret);
    }
    wake_up(&io_data->wait);
}
```

**5. Returning Status**
```c
static void ffs_user_copy_worker(struct work_struct *work)
{
    struct ffs_io_data *io_data = container_of(work, struct ffs_io_data, work);
    int ret = io_data->status;

    if (ret != 0) {
        printk(KERN_ERR "ffs_user_copy_worker: error %d\n", ret);
    }
    io_data->callback(ret);
}
```

Note: These are just examples and the actual code completion will depend on the specific requirements of your project.