valid              18 file.h           int valid;          // inode has been read from disk?
valid             268 fs.c             ip->valid = 0;
valid             298 fs.c             if(ip->valid == 0){
valid             308 fs.c               ip->valid = 1;
valid             335 fs.c             if(ip->valid && ip->nlink == 0){
valid             344 fs.c                 ip->valid = 0;