rem: return ENOMEM;
add: return FS_ENOMEM;
context: mkfile(char *s, int sz){    int  fd, len;    int err = 0;	char *buffer;    if ((fd = sys_open(1, -1, s, O_RDWR|O_CREAT,                       MY_S_IFREG|MY_S_IRWXU, 0)) < 0) {        printf("error creating: %s\n", s);        return fd;    }	buffer = (char*)malloc(16 * 1024);	if (buffer == NULL)		return ENOMEM;    len = sz;    if (sz) {    	err = sys_write(1, fd, buffer, len);        if (err != len)            printf("error writing %d bytes to %s\n", sz, s);    }    if (sys_close(1, fd) != 0)        printf("close failed?\n");	free(buffer);	return (err < 0 ? err : 0);}