> +static int loop_global_lock_killable(struct loop_device *lo, bool global)
> +{
> + int err;
> +
> + if (global) {
> + err = mutex_lock_killable(&loop_validate_mutex);
> + if (err)
> + return err;
> + }
> + err = mutex_lock_killable(&lo->lo_mutex);
> + if (err && global)
> + mutex_unlock(&loop_validate_mutex);
> + return err;
> +}
> +
> +static void loop_global_unlock(struct loop_device *lo, bool global)
> +{
> + mutex_unlock(&lo->lo_mutex);
> + if (global)
> + mutex_unlock(&loop_validate_mutex);
> +}
Comments explaining these functions would be nice.
> static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
> unsigned int arg)
> {
> - struct file *file = NULL, *old_file;
> + struct file *file = fget(arg);
> + struct file *old_file;
> int error;
> bool partscan;
> + bool is_loop;
This doesn't match the existing formatting. Either keep the existing
one or change the few other variables as well.
> + is_loop = is_loop_device(file);
> + error = loop_global_lock_killable(lo, is_loop);
> + if (error) {
> + fput(file);
> return error;
> + }
Please use a goto label to share the fput with the other error handling.
> @@ -1143,6 +1167,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
> loff_t size;
> bool partscan;
> unsigned short bsize;
> + bool is_loop;
Please follow the existing formatting.
Otherwise this looks reasonable to me.
