readable          111 kernel/file.c    if (f->readable == 0 || n < 0)
readable            4 kernel/file.h    char readable;
readable           39 kernel/pipe.c    (*f0)->readable = 1;
readable           43 kernel/pipe.c    (*f1)->readable = 0;
readable          384 kernel/sysfile.c   f->readable = !(omode & O_WRONLY);