namei returns locked parent dir inode for create / unlink
don't hold fd table lock across idecref() (latter does block i/o) idecref calls iput() in case last ref -> freeing inode dir size is 512 * # blocks, so readi/writei &c work unlink deletes dirent even if ip->nlink > 0
This commit is contained in:
rtm
parent
c372e8dc34
commit
211ff0c67e
7 changed files with 122 additions and 84 deletions
15
Notes
15
Notes
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@ -365,3 +365,18 @@ two bugs in unlink: don't just return if nlink > 0,
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and search for name, not inum
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is there a create/create race for same file name?
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resulting in two entries w/ same name in directory?
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namei
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return just inode
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return offset in dir where found, w/ dir locked, for unlink
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return dir locked, for mknod
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is the offset alone useful? how do I read/write it?
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test: one process unlinks a file while another links to it
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test: simultaneous create of same file
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test: one process opens a file while another deletes it
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oy, mkfs wants dir size to be last written entry, but i
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want it to be nblocks*512
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maybe fix kernel code to handle former
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2
defs.h
2
defs.h
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@ -116,7 +116,7 @@ void ilock(struct inode *ip);
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void iunlock(struct inode *ip);
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void idecref(struct inode *ip);
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void iput(struct inode *ip);
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struct inode * namei(char *path, uint *);
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struct inode * namei(char *path, int, uint *);
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void stati(struct inode *ip, struct stat *st);
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int readi(struct inode *ip, char *xdst, uint off, uint n);
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int writei(struct inode *ip, char *addr, uint off, uint n);
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20
fd.c
20
fd.c
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@ -108,18 +108,22 @@ fd_close(struct fd *fd)
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panic("fd_close");
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if(--fd->ref == 0){
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if(fd->type == FD_PIPE){
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pipe_close(fd->pipe, fd->writeable);
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} else if(fd->type == FD_FILE){
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idecref(fd->ip);
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struct fd dummy = *fd;
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fd->ref = 0;
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fd->type = FD_CLOSED;
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release(&fd_table_lock);
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if(dummy.type == FD_PIPE){
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pipe_close(dummy.pipe, dummy.writeable);
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} else if(dummy.type == FD_FILE){
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idecref(dummy.ip);
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} else {
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panic("fd_close");
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}
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fd->ref = 0;
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fd->type = FD_CLOSED;
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} else {
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release(&fd_table_lock);
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}
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release(&fd_table_lock);
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}
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int
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153
fs.c
153
fs.c
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@ -286,14 +286,8 @@ iput(struct inode *ip)
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void
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idecref(struct inode *ip)
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{
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acquire(&inode_table_lock);
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if(ip->count < 1)
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panic("idecref");
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ip->count -= 1;
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release(&inode_table_lock);
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ilock(ip);
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iput(ip);
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}
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void
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@ -376,34 +370,37 @@ writei(struct inode *ip, char *addr, uint off, uint n)
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}
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}
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// look up a path name, in one of three modes.
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// NAMEI_LOOKUP: return locked target inode.
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// NAMEI_CREATE: return locked parent inode.
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// but return 0 if name does exist.
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// NAMEI_DELETE: return locked parent inode, offset of dirent in *ret_off.
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// return 0 if name doesn't exist.
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struct inode *
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namei(char *path, uint *ret_pinum)
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namei(char *path, int mode, uint *ret_off)
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{
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struct inode *dp;
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char *cp = path;
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char *cp = path, *cp1;
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uint off, dev;
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struct buf *bp;
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struct dirent *ep;
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int i;
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int i, atend;
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unsigned ninum;
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unsigned pinum;
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dp = iget(rootdev, 1);
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pinum = dp->inum;
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while(*cp == '/')
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cp++;
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while(1){
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if(*cp == '\0') {
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if (ret_pinum)
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*ret_pinum = pinum;
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return dp;
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if(*cp == '\0'){
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if(mode == NAMEI_LOOKUP)
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return dp;
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iput(dp);
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return 0;
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}
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if(dp->type != T_DIR){
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if (ret_pinum)
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*ret_pinum = pinum;
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iput(dp);
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return 0;
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}
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@ -419,6 +416,7 @@ namei(char *path, uint *ret_pinum)
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if(cp[i] != ep->name[i])
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break;
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if((cp[i] == '\0' || cp[i] == '/') && (i >= DIRSIZ || ep->name[i] == '\0')){
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off += (uchar*)ep - bp->data;
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ninum = ep->inum;
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brelse(bp);
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cp += i;
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@ -427,14 +425,22 @@ namei(char *path, uint *ret_pinum)
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}
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brelse(bp);
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}
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atend = 1;
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for(cp1 = cp; *cp1; cp1++)
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if(*cp1 == '/')
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atend = 0;
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if(mode == NAMEI_CREATE && atend)
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return dp;
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iput(dp);
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if (ret_pinum)
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*ret_pinum = pinum;
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return 0;
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found:
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if(mode == NAMEI_DELETE && *cp == '\0'){
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*ret_off = off;
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return dp;
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}
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dev = dp->dev;
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pinum = dp->inum;
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iput(dp);
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dp = iget(dev, ninum);
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if(dp->type == 0 || dp->nlink < 1)
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@ -453,6 +459,9 @@ wdir(struct inode *dp, char *name, uint ino)
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int i;
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int lb;
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if(dp->size % BSIZE)
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dp->size += (BSIZE - dp->size % BSIZE);
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for(off = 0; off < dp->size; off += BSIZE) {
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bp = bread(dp->dev, bmap(dp, off / BSIZE));
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for(ep = (struct dirent *) bp->data;
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@ -469,14 +478,16 @@ wdir(struct inode *dp, char *name, uint ino)
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}
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dp->addrs[lb] = balloc(dp->dev);
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bp = bread(dp->dev, dp->addrs[lb]);
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memset(bp->data, 0, BSIZE);
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ep = (struct dirent *) (bp->data);
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dp->size += BSIZE;
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found:
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ep->inum = ino;
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for(i = 0; i < DIRSIZ && name[i]; i++)
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ep->name[i] = name[i];
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for( ; i < DIRSIZ; i++)
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ep->name[i] = '\0';
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dp->size += sizeof(struct dirent);
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bwrite (bp, bmap(dp, off/BSIZE)); // write directory block
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brelse(bp);
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iupdate(dp);
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@ -486,15 +497,12 @@ struct inode *
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mknod(char *cp, short type, short major, short minor)
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{
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struct inode *ip, *dp;
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uint pinum = 0;
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cprintf("mknod: %s %d %d %d\n", cp, type, major, minor);
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if ((ip = namei(cp, &pinum)) != 0) {
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iput(ip);
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if ((dp = namei(cp, NAMEI_CREATE, 0)) == 0)
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return 0;
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}
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dp = iget(rootdev, pinum);
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ip = ialloc(dp->dev, type);
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if (ip == 0) {
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iput(dp);
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@ -515,74 +523,81 @@ mknod(char *cp, short type, short major, short minor)
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int
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unlink(char *cp)
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{
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struct inode *ip;
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struct inode *dp;
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struct dirent *ep = 0;
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int off;
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struct buf *bp = 0;
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uint pinum;
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struct inode *ip, *dp;
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struct dirent de;
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uint off, inum, cc;
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cprintf("unlink(%s)\n", cp);
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if ((ip = namei(cp, &pinum)) == 0) {
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if ((dp = namei(cp, NAMEI_DELETE, &off)) == 0) {
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cprintf("unlink(%s) it doesn't exist\n", cp);
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return -1;
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}
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ip->nlink--;
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if (ip->nlink > 0) {
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iput(ip);
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return 0;
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if((cc = readi(dp, (char*)&de, off, sizeof(de))) != sizeof(de) ||
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de.inum == 0){
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cprintf("off %d dp->size %d cc %d de.inum %d",
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off, dp->size, cc, de.inum);
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panic("unlink no entry");
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}
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inum = de.inum;
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cprintf("dinum %d off %d de %s/%d\n",
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dp->inum, off, de.name, de.inum);
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dp = iget(rootdev, pinum);
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for(off = 0; off < dp->size; off += BSIZE) {
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bp = bread(dp->dev, bmap(dp, off / BSIZE));
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for(ep = (struct dirent *) bp->data;
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ep < (struct dirent *) (bp->data + BSIZE);
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ep++){
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if(ep->inum == ip->inum) {
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goto found;
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}
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}
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brelse(bp);
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}
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panic("unlink: entry doesn't exist\n");
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memset(&de, 0, sizeof(de));
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if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
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panic("unlink dir write");
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found:
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ep->inum = 0;
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memset(ep->name, '\0', DIRSIZ);
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bwrite (bp, bmap(dp, off/BSIZE)); // write directory block
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brelse(bp);
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dp->size -= sizeof(struct dirent);
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iupdate (dp);
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iupdate(dp);
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iput(dp);
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ip = iget(dp->dev, inum);
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if(ip == 0)
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panic("unlink no inode");
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ip->nlink--;
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iupdate(ip);
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iput(ip);
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return 0;
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}
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int
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link(char *name1, char *name2)
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{
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struct inode *ip, *dp, *xip;
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uint pinum = 0;
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struct inode *ip, *dp;
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cprintf("link(%s, %s)\n", name1, name2);
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if ((xip = namei(name2, &pinum)) != 0) {
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cprintf(" failed %s exists\n", name2);
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iput(xip);
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return -1;
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}
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if ((ip = namei(name1, &pinum)) == 0){
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if ((ip = namei(name1, NAMEI_LOOKUP, 0)) == 0){
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cprintf(" failed %s does not exist\n", name1);
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return -1;
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}
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if(ip->type == T_DIR){
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cprintf(" failed %s is a dir\n", name1);
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iput(ip);
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return -1;
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}
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iunlock(ip);
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if ((dp = namei(name2, NAMEI_CREATE, 0)) == 0) {
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cprintf(" failed %s exists\n", name2);
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idecref(ip);
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return -1;
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}
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if(dp->dev != ip->dev){
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cprintf(" cross-device link\n");
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idecref(ip);
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iput(dp);
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return -1;
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}
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ilock(ip);
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ip->nlink += 1;
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iupdate (ip);
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dp = iget(rootdev, pinum);
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wdir(dp, name2, ip->inum);
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iput(dp);
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iput(ip);
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4
fsvar.h
4
fsvar.h
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@ -14,3 +14,7 @@ struct inode {
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};
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extern uint rootdev;
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#define NAMEI_LOOKUP 1
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#define NAMEI_CREATE 2
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#define NAMEI_DELETE 3
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@ -228,7 +228,7 @@ sys_open(void)
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return -1;
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if((l = checkstring(arg0)) < 0)
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return -1;
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if((ip = namei(cp->mem + arg0, 0)) == 0) {
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if((ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0)) == 0) {
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if (arg1 & O_CREATE) {
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if (l >= DIRSIZ)
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return -1;
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@ -356,7 +356,7 @@ sys_exec(void)
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return -1;
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if(checkstring(arg0) < 0)
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return -1;
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ip = namei(cp->mem + arg0, 0);
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ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0);
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if(ip == 0)
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return -1;
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@ -494,7 +494,7 @@ sys_block(void)
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ip->type, ip->nlink, ip->size, ip->addrs[0]);
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iput(ip);
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ip = namei(".././//./../usertests", 0);
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ip = namei(".././//./../usertests", NAMEI_LOOKUP, 0);
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if(ip){
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cprintf("namei(usertests): %d %d %d %d %d %d %d %d\n",
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ip->dev, ip->inum, ip->count, ip->busy,
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@ -231,7 +231,7 @@ void
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createdelete()
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{
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int pid, i, fd;
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int n = 10; // for now, fit in one directory block
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int n = 20;
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char name[32];
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pid = fork();
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