단일연결리스트에서 링크부분을 교환할때의 문제입니다.

//링크드리스트에 들어있는자료를 파일이름순으로 정렬
void sort_list(FILEINFO *list_head)
{	
	FILEINFO *prev;
	FILEINFO *tmp_list_left;
	FILEINFO *tmp_list_right;
 
	prev = (FILEINFO*)malloc(sizeof(FILEINFO));
	prev->next = list_head;
 
	int change = 1;
 
 
	if(list_head == NULL || list_head->next == NULL)
		return ;
 
	tmp_list_left = prev->next;
	printf("%s\n", tmp_list_left->filename); //o
	tmp_list_right = prev->next->next; 
	printf("%s\n", tmp_list_right->filename); //o
 
	while(change) {
		change = 0;	
		printf("%s\n", tmp_list_left->filename); //o
		printf("%s\n", tmp_list_right->filename); //o
		while(tmp_list_right != NULL) {	
			if(flag_r) {	
				printf("%s\n", list_head->filename);
				if(strcmp(tmp_list_left->filename, tmp_list_right->filename) < 0) {
					prev->next = tmp_list_left->next;
					tmp_list_left->next = tmp_list_right->next;
					tmp_list_right->next = tmp_list_left;
 
					change = 1;
					//puts("==========================");
 
				}
				if(change == 1) {
					prev = tmp_list_right;
					tmp_list_right = tmp_list_left->next;
				}else {
					prev = tmp_list_left;
					tmp_list_left = tmp_list_right;
					tmp_list_right = tmp_list_left->next;
				}
			} 
			else {
				printf("%s\n", tmp_list_left->filename);
				if(strcmp(tmp_list_left->filename, tmp_list_right->filename) > 0 ) {	
					prev->next = tmp_list_left->next;
					tmp_list_left->next = tmp_list_right->next;
					tmp_list_right->next = tmp_list_left;
					change = 1;
					puts("==================");
				}
				if(change == 1) {
					prev = prev->next;
					tmp_list_right = tmp_list_left->next;
				}else {
					prev = prev->next;
					tmp_list_left = tmp_list_left->next;
					tmp_list_right = tmp_list_right->next;
				}
			}
		}
		prev->next = list_head;
		tmp_list_left = prev->next;
		tmp_list_right = prev->next->next;
	}
}
<//code>