X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/7f606d199c99350ab9dbc57bbe8304d946b93d71..7e2a7a5c8fd83ec48fdef829aa44ff92c1717fbb:/usr/src/sys/kern/vfs_lookup.c

diff --git a/usr/src/sys/kern/vfs_lookup.c b/usr/src/sys/kern/vfs_lookup.c
index 7cb0879d0d..d42e01209c 100644
--- a/usr/src/sys/kern/vfs_lookup.c
+++ b/usr/src/sys/kern/vfs_lookup.c
@@ -1,230 +1,750 @@
-/*	vfs_lookup.c	3.4	%G%	*/
+/*	vfs_lookup.c	4.34	82/12/22	*/
 
 #include "../h/param.h"
 #include "../h/systm.h"
 #include "../h/inode.h"
+#include "../h/fs.h"
 #include "../h/mount.h"
 #include "../h/dir.h"
 #include "../h/user.h"
 #include "../h/buf.h"
+#include "../h/conf.h"
+#include "../h/uio.h"
+#include "../h/nami.h"
 
+struct	buf *blkatoff();
+int	dirchk = 0;
 /*
- * Convert a pathname into a pointer to
- * an inode. Note that the inode is locked.
+ * Convert a pathname into a pointer to a locked inode,
+ * with side effects usable in creating and removing files.
+ * This is a very central and rather complicated routine.
  *
- * func = function called to get next char of name
- *	&uchar if name is in user space
- *	&schar if name is in system space
- * flag = 0 if name is sought
- *	1 if name is to be created
- *	2 if name is to be deleted
+ * The func argument gives the routine which returns successive
+ * characters of the name to be translated. 
+ *
+ * The flag argument is (LOOKUP, CREATE, DELETE) depending on whether
+ * the name is to be (looked up, created, deleted).  If flag has
+ * LOCKPARENT or'ed into it and the target of the pathname exists,
+ * namei returns both the target and its parent directory locked. 
+ * If the file system is not maintained in a strict tree hierarchy,
+ * this can result in a deadlock situation.  When creating and
+ * LOCKPARENT is specified, the target may not be ".".  When deleting
+ * and LOCKPARENT is specified, the target may be ".", but the caller
+ * must check to insure it does an irele and iput instead of two iputs.
+ *
+ * The follow argument is 1 when symbolic links are to be followed
+ * when they occur at the end of the name translation process.
+ *
+ * Overall outline:
+ *
+ *	copy in name
+ *	get starting directory
+ * dirloop:
+ *	check accessibility of directory
+ * dirloop2:
+ *	copy next component of name to u.u_dent
+ *	handle degenerate case where name is null string
+ *	search for name in directory, to found or notfound
+ * notfound:
+ *	if creating, return locked directory, leaving info on avail. slots
+ *	else return error
+ * found:
+ *	if at end of path and deleting, return information to allow delete
+ *	if at end of path and rewriting (create and LOCKPARENT), lock targe
+ *	  inode and return info to allow rewrite
+ *	if .. and on mounted filesys, look in mount table for parent
+ *	if symbolic link, massage name in buffer and continue at dirloop
+ *	if more components of name, do next level at dirloop
+ *	return the answer as locked inode
+ *
+ * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode,
+ *	 but unlocked.
  */
 struct inode *
-namei(func, flag)
-int (*func)();
+namei(func, flag, follow)
+	int (*func)(), flag, follow;
 {
-	register struct inode *dp;
-	register c;
-	register char *cp;
-	struct buf *bp;
-	register struct direct *ep;
+	register char *cp;		/* pointer into pathname argument */
+/* these variables refer to things which must be freed or unlocked */
+	register struct inode *dp = 0;	/* the directory we are searching */
+	register struct fs *fs;		/* file system that directory is in */
+	register struct buf *bp = 0;	/* a buffer of directory entries */
+	register struct direct *ep;	/* the current directory entry */
+	int entryoffsetinblock;		/* offset of ep in bp's buffer */
+	register struct buf *nbp;	/* buffer storing path name argument */
+/* these variables hold information about the search for a slot */
+	enum {NONE, COMPACT, FOUND} slotstatus;
+	int slotoffset = -1;		/* offset of area with free space */
+	int slotsize;			/* size of area at slotoffset */
+	int slotfreespace;		/* amount of space free in slot */
+	int slotneeded;			/* size of the entry we're seeking */
+/* */
+	int dirsize;
+	int prevoff;			/* u.u_offset of previous entry */
+	int nlink = 0;			/* number of symbolic links taken */
+	struct inode *pdp;		/* saved dp during symlink work */
 	int i;
-	dev_t d;
-	off_t eo;
+	int lockparent;
 
+	lockparent = flag & LOCKPARENT;
+	flag &= ~LOCKPARENT;
 	/*
-	 * If name starts with '/' start from
-	 * root; otherwise start from current dir.
+	 * Get a buffer for the name to be translated, and copy the
+	 * name into the buffer.
 	 */
+	nbp = geteblk(MAXPATHLEN);
+	for (cp = nbp->b_un.b_addr; *cp = (*func)(); ) {
+		if ((*cp&0377) == ('/'|0200) || (*cp&0200) && flag != 2) {
+			u.u_error = EPERM;
+			goto bad;
+		}
+		cp++;
+		if (cp >= nbp->b_un.b_addr + MAXPATHLEN) {
+			u.u_error = ENOENT;
+			goto bad;
+		}
+	}
+	if (u.u_error)
+		goto bad;
 
-	dp = u.u_cdir;
-	if((c=(*func)()) == '/')
+	/*
+	 * Get starting directory.
+	 */
+	cp = nbp->b_un.b_addr;
+	if (*cp == '/') {
+		while (*cp == '/')
+			cp++;
 		if ((dp = u.u_rdir) == NULL)
 			dp = rootdir;
-	(void) iget(dp->i_dev, dp->i_number);
-	while(c == '/')
-		c = (*func)();
-	if(c == '\0' && flag != 0)
-		u.u_error = ENOENT;
+	} else
+		dp = u.u_cdir;
+	fs = dp->i_fs;
+	ilock(dp);
+	dp->i_count++;
+	u.u_pdir = (struct inode *)0xc0000000;		/* illegal */
 
-cloop:
 	/*
-	 * Here dp contains pointer
-	 * to last component matched.
+	 * We come to dirloop to search a new directory.
+	 * The directory must be locked so that it can be
+	 * iput, and fs must be already set to dp->i_fs.
 	 */
-
-	if(u.u_error)
-		goto out;
-	if(c == '\0')
-		return(dp);
-
+dirloop:
 	/*
-	 * If there is another component,
-	 * Gather up name into
-	 * users' dir buffer.
+	 * Check accessiblity of directory.
 	 */
+	if ((dp->i_mode&IFMT) != IFDIR) {
+		u.u_error = ENOTDIR;
+		goto bad;
+	}
+	if (access(dp, IEXEC))
+		goto bad;
 
-	cp = &u.u_dbuf[0];
-	while (c != '/' && c != '\0' && u.u_error == 0 ) {
-		if (mpxip!=NULL && c=='!')
-			break;
-		if (cp < &u.u_dbuf[DIRSIZ])
-			*cp++ = c;
-		c = (*func)();
+dirloop2:
+	/*
+	 * Copy next component of name to u.u_dent.
+	 */
+	for (i = 0; *cp != 0 && *cp != '/'; cp++) {
+		if (i >= MAXNAMLEN) {
+			u.u_error = ENOENT;
+			goto bad;
+		}
+		u.u_dent.d_name[i++] = *cp;
 	}
-	while(cp < &u.u_dbuf[DIRSIZ])
-		*cp++ = '\0';
-	while(c == '/')
-		c = (*func)();
-	if (c == '!' && mpxip != NULL) {
-		iput(dp);
-		plock(mpxip);
-		mpxip->i_count++;
-		return(mpxip);
+	u.u_dent.d_namlen = i;
+	u.u_dent.d_name[i] = 0;
+
+	/*
+	 * Check for degenerate name (e.g. / or "")
+	 * which is a way of talking about a directory,
+	 * e.g. like "/." or ".".
+	 */
+	if (u.u_dent.d_name[0] == 0) {
+		if (flag || lockparent) {
+			u.u_error = ENOENT;
+			goto bad;
+		}
+		brelse(nbp);
+		return (dp);
 	}
 
-seloop:
 	/*
-	 * dp must be a directory and
-	 * must have X permission.
+	 * Suppress search for slots unless creating
+	 * file and at end of pathname, in which case
+	 * we watch for a place to put the new file in
+	 * case it doesn't already exist.
 	 */
+	slotstatus = FOUND;
+	if (flag == CREATE && *cp == 0) {
+		slotstatus = NONE;
+		slotfreespace = 0;
+		slotneeded = DIRSIZ(&u.u_dent);
+	}
 
-	if((dp->i_mode&IFMT) != IFDIR)
-		u.u_error = ENOTDIR;
-	(void) access(dp, IEXEC);
-	if(u.u_error)
-		goto out;
+	dirsize = roundup(dp->i_size, DIRBLKSIZ);
+	u.u_offset = 0;
+	while (u.u_offset < dirsize) {
+		/*
+		 * If offset is on a block boundary,
+		 * read the next directory block.
+		 * Release previous if it exists.
+		 */
+		if (blkoff(fs, u.u_offset) == 0) {
+			if (bp != NULL)
+				brelse(bp);
+			bp = blkatoff(dp, u.u_offset, (char **)0);
+			if (bp == 0)
+				goto bad;
+			entryoffsetinblock = 0;
+		}
+
+		/*
+		 * If still looking for a slot, and at a DIRBLKSIZE
+		 * boundary, have to start looking for free space
+		 * again.
+		 */
+		if (slotstatus == NONE &&
+		    (entryoffsetinblock&(DIRBLKSIZ-1)) == 0) {
+			slotoffset = -1;
+			slotfreespace = 0;
+		}
+
+		/*
+		 * Get pointer to next entry, and do consistency checking:
+		 *	record length must be multiple of 4
+		 *	record length must not be zero
+		 *	entry must fit in rest of this DIRBLKSIZ block
+		 *	record must be large enough to contain name
+		 * When dirchk is set we also check:
+		 *	name is not longer than MAXNAMLEN
+		 *	name must be as long as advertised, and null terminated
+		 * Checking last two conditions is done only when dirchk is
+		 * set, to save time.
+		 */
+		ep = (struct direct *)(bp->b_un.b_addr + entryoffsetinblock);
+		i = DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1));
+		if ((ep->d_reclen & 0x3) || ep->d_reclen == 0 ||
+		    ep->d_reclen > i || DIRSIZ(ep) > ep->d_reclen ||
+		    dirchk && (ep->d_namlen > MAXNAMLEN || dirbadname(ep))) {
+			dirbad(dp, "mangled entry");
+			u.u_offset += i;
+			entryoffsetinblock += i;
+			continue;
+		}
 
+		/*
+		 * If an appropriate sized slot has not yet been found,
+		 * check to see if one is available. Also accumulate space
+		 * in the current block so that we can determine if
+		 * compaction is viable.
+		 */
+		if (slotstatus != FOUND) {
+			int size = ep->d_reclen;
+
+			if (ep->d_ino != 0)
+				size -= DIRSIZ(ep);
+			if (size > 0) {
+				if (size >= slotneeded) {
+					slotstatus = FOUND;
+					slotoffset = u.u_offset;
+					slotsize = ep->d_reclen;
+				} else if (slotstatus == NONE) {
+					slotfreespace += size;
+					if (slotoffset == -1)
+						slotoffset = u.u_offset;
+					if (slotfreespace >= slotneeded) {
+						slotstatus = COMPACT;
+						slotsize =
+						    u.u_offset+ep->d_reclen -
+						      slotoffset;
+					}
+				}
+			}
+		}
+
+		/*
+		 * Check for a name match.
+		 */
+		if (ep->d_ino) {
+			if (ep->d_namlen == u.u_dent.d_namlen &&
+			    !bcmp(u.u_dent.d_name, ep->d_name, ep->d_namlen))
+				goto found;
+		}
+		prevoff = u.u_offset;
+		u.u_offset += ep->d_reclen;
+		entryoffsetinblock += ep->d_reclen;
+	}
+/* notfound: */
 	/*
-	 * set up to search a directory
+	 * If creating, and at end of pathname and current
+	 * directory has not been removed, then can consider
+	 * allowing file to be created.
 	 */
-	u.u_offset = 0;
-	u.u_segflg = 1;
-	eo = 0;
+	if (flag == CREATE && *cp == 0 && dp->i_nlink != 0) {
+		/*
+		 * Access for write is interpreted as allowing
+		 * creation of files in the directory.
+		 */
+		if (access(dp, IWRITE))
+			goto bad;
+		/*
+		 * Return an indication of where the new directory
+		 * entry should be put.  If we didn't find a slot,
+		 * then set u.u_count to 0 indicating that the
+		 * new slot belongs at the end of the directory.
+		 * If we found a slot, then the new entry can be
+		 * put in the range [u.u_offset..u.u_offset+u.u_count)
+		 */
+		if (slotstatus == NONE)
+			u.u_count = 0;
+		else {
+			u.u_offset = slotoffset;
+			u.u_count = slotsize;
+		}
+		dp->i_flag |= IUPD|ICHG;
+		if (bp)
+			brelse(bp);
+		brelse(nbp);
+		/*
+		 * We return with the directory locked, so that
+		 * the parameters we set up above will still be
+		 * valid if we actually decide to do a direnter().
+		 * We return NULL to indicate that the entry doesn't
+		 * currently exist, leaving a pointer to the (locked)
+		 * directory inode in u.u_pdir.
+		 */
+		u.u_pdir = dp;
+		return (NULL);
+	}
+	u.u_error = ENOENT;
+	goto bad;
+found:
+	/*
+	 * Check that directory length properly reflects presence
+	 * of this entry.
+	 */
+	if (entryoffsetinblock + DIRSIZ(ep) > dp->i_size) {
+		dirbad(dp, "i_size too small");
+		dp->i_size = entryoffsetinblock + DIRSIZ(ep);
+		dp->i_flag |= IUPD|ICHG;
+	}
+
+	/*
+	 * Found component in pathname; save directory
+	 * entry in u.u_dent, and release directory buffer.
+	 */
+	bcopy((caddr_t)ep, (caddr_t)&u.u_dent, (u_int)DIRSIZ(ep));
+	brelse(bp);
 	bp = NULL;
 
-eloop:
+	/*
+	 * If deleting, and at end of pathname, return
+	 * parameters which can be used to remove file.
+	 * If the lockparent flag isn't set, we return only
+	 * the directory (in u.u_pdir), otherwise we go
+	 * on and lock the inode, being careful with ".".
+	 */
+	if (flag == DELETE && *cp == 0) {
+		/*
+		 * Write access to directory required to delete files.
+		 */
+		if (access(dp, IWRITE))
+			goto bad;
+		u.u_pdir = dp;		/* for dirremove() */
+		/*
+		 * Return pointer to current entry in u.u_offset,
+		 * and distance past previous entry (if there
+		 * is a previous entry in this block) in u.u_count.
+		 * Save directory inode pointer in u.u_pdir for dirremove().
+		 */
+		if ((u.u_offset&(DIRBLKSIZ-1)) == 0)
+			u.u_count = 0;
+		else
+			u.u_count = u.u_offset - prevoff;
+		if (lockparent) {
+			if (dp->i_number == u.u_dent.d_ino)
+				dp->i_count++;
+			else {
+				dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
+				if (dp == NULL) {
+					iput(u.u_pdir);
+					goto bad;
+				}
+			}
+		}
+		brelse(nbp);
+		return (dp);
+	}
 
 	/*
-	 * If at the end of the directory,
-	 * the search failed. Report what
-	 * is appropriate as per flag.
+	 * Special handling for ".." allowing chdir out of mounted
+	 * file system: indirect .. in root inode to reevaluate
+	 * in directory file system was mounted on.
 	 */
+	if (u.u_dent.d_name[0] == '.' && u.u_dent.d_name[1] == '.' &&
+	    u.u_dent.d_name[2] == '\0') {
+		if (dp == u.u_rdir)
+			u.u_dent.d_ino = dp->i_number;
+		else if (u.u_dent.d_ino == ROOTINO &&
+		   dp->i_number == ROOTINO) {
+			for (i = 1; i < NMOUNT; i++)
+			if (mount[i].m_bufp != NULL &&
+			   mount[i].m_dev == dp->i_dev) {
+				iput(dp);
+				dp = mount[i].m_inodp;
+				ilock(dp);
+				dp->i_count++;
+				fs = dp->i_fs;
+				cp -= 2;     /* back over .. */
+				goto dirloop2;
+			}
+		}
+	}
 
-	if(u.u_offset >= dp->i_size) {
-		if(bp != NULL)
-			brelse(bp);
-		if(flag==1 && c=='\0' && dp->i_nlink) {
-			if(access(dp, IWRITE))
-				goto out;
-			u.u_pdir = dp;
-			if(eo)
-				u.u_offset = eo-sizeof(struct direct);
-			else
-				dp->i_flag |= IUPD|ICHG;
-			return(NULL);
+	/*
+	 * If rewriting (rename), return the inode and the
+	 * information required to rewrite the present directory
+	 * Must get inode of directory entry to verify it's a
+	 * regular file, or empty directory.  
+	 */
+	if ((flag == CREATE && lockparent) && *cp == 0) {
+		if (access(dp, IWRITE))
+			goto bad;
+		u.u_pdir = dp;		/* for dirrewrite() */
+		/*
+		 * Careful about locking second inode. 
+		 * This can only occur if the target is ".". 
+		 */
+		if (dp->i_number == u.u_dent.d_ino) {
+			u.u_error = EISDIR;		/* XXX */
+			goto bad;
 		}
-		u.u_error = ENOENT;
-		goto out;
+		dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
+		if (dp == NULL) {
+			iput(u.u_pdir);
+			goto bad;
+		}
+		brelse(nbp);
+		return (dp);
 	}
 
 	/*
-	 * If offset is on a block boundary,
-	 * read the next directory block.
-	 * Release previous if it exists.
+	 * Check for symbolic link, which may require us
+	 * to massage the name before we continue translation.
+	 * To avoid deadlock have to unlock the current directory,
+	 * but don't iput it because we may need it again (if
+	 * the symbolic link is relative to .).  Instead save
+	 * it (unlocked) as pdp.
 	 */
+	pdp = dp;
+	iunlock(pdp);
+	dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
+	if (dp == NULL)
+		goto bad2;
+	fs = dp->i_fs;
 
-	if((u.u_offset&BMASK) == 0) {
-		if(bp != NULL)
-			brelse(bp);
-		bp = bread(dp->i_dev,
-			bmap(dp, (daddr_t)(u.u_offset>>BSHIFT), B_READ));
-		if (bp->b_flags & B_ERROR) {
-			brelse(bp);
-			goto out;
+	/*
+	 * Check for symbolic link
+	 */
+	if ((dp->i_mode & IFMT) == IFLNK && (follow || *cp == '/')) {
+		u_int pathlen = strlen(cp) + 1;
+
+		if (dp->i_size + pathlen >= MAXPATHLEN - 1 ||
+		    ++nlink > MAXSYMLINKS) {
+			u.u_error = ELOOP;
+			goto bad2;
 		}
-		ep = (struct direct *)bp->b_un.b_addr;
-	} else
-		ep++;
+		ovbcopy(cp, nbp->b_un.b_addr + dp->i_size, pathlen);
+		u.u_error =
+		    rdwri(UIO_READ, dp, nbp->b_un.b_addr, (int)dp->i_size,
+			0, 1, (int *)0);
+		if (u.u_error)
+			goto bad2;
+		cp = nbp->b_un.b_addr;
+		iput(dp);
+		if (*cp == '/') {
+			irele(pdp);
+			while (*cp == '/')
+				cp++;
+			if ((dp = u.u_rdir) == NULL)
+				dp = rootdir;
+			ilock(dp);
+			dp->i_count++;
+		} else {
+			dp = pdp;
+			ilock(dp);
+		}
+		fs = dp->i_fs;
+		goto dirloop;
+	}
 
 	/*
-	 * Note first empty directory slot
-	 * in eo for possible creat.
-	 * String compare the directory entry
-	 * and the current component.
-	 * If they do not match, go back to eloop.
+	 * Not a symbolic link.  If more pathname,
+	 * continue at next component, else return.
 	 */
+	if (*cp == '/') {
+		while (*cp == '/')
+			cp++;
+		irele(pdp);
+		goto dirloop;
+	}
+	brelse(nbp);
+	if (lockparent)
+		u.u_pdir = pdp;
+	else
+		irele(pdp);
+	return (dp);
+bad2:
+	irele(pdp);
+bad:
+	if (bp)
+		brelse(bp);
+	if (dp)
+		iput(dp);
+	brelse(nbp);
+	return (NULL);
+}
+
+dirbad(ip, how)
+	struct inode *ip;
+	char *how;
+{
 
-	u.u_offset += sizeof(struct direct);
-	if(ep->d_ino == 0) {
-		if(eo == 0)
-			eo = u.u_offset;
-		goto eloop;
+	printf("%s: bad dir ino %d at offset %d: %s\n",
+	    ip->i_fs->fs_fsmnt, ip->i_number, u.u_offset, how);
+}
+
+dirbadname(ep)
+	register struct direct *ep;
+{
+	register int i;
+
+	for (i = 0; i < ep->d_namlen; i++)
+		if (ep->d_name[i] == 0)
+			return (1);
+	return (ep->d_name[i]);
+}
+
+/*
+ * Write a directory entry after a call to namei, using the parameters
+ * which it left in the u. area.  The argument ip is the inode which
+ * the new directory entry will refer to.  The u. area field u.u_pdir is
+ * a pointer to the directory to be written, which was left locked by
+ * namei.  Remaining parameters (u.u_offset, u.u_count) indicate
+ * how the space for the new entry is to be gotten.
+ */
+direnter(ip)
+	struct inode *ip;
+{
+	register struct direct *ep, *nep;
+	struct buf *bp;
+	int loc, freespace;
+	u_int dsize;
+	int newentrysize;
+	char *dirbuf;
+
+	u.u_dent.d_ino = ip->i_number;
+	u.u_segflg = 1;
+	newentrysize = DIRSIZ(&u.u_dent);
+	if (u.u_count == 0) {
+		/*
+		 * If u.u_count is 0, then namei could find no space in the
+		 * directory.  In this case u.u_offset will be on a directory
+		 * block boundary and we will write the new entry into a fresh
+		 * block.
+		 */
+		if (u.u_offset&(DIRBLKSIZ-1))
+			panic("wdir: newblk");
+		u.u_dent.d_reclen = DIRBLKSIZ;
+		(void) rdwri(UIO_WRITE, u.u_pdir, (caddr_t)&u.u_dent,
+		    newentrysize, u.u_offset, 1, (int *)0);
+		iput(u.u_pdir);
+		return;
 	}
-	for(i=0; i<DIRSIZ; i++) {
-		if(u.u_dbuf[i] != ep->d_name[i])
-			goto eloop;
-		if(u.u_dbuf[i] == 0)
-			break;
+
+	/*
+	 * If u.u_count is non-zero, then namei found space for the
+	 * new entry in the range u.u_offset to u.u_offset+u.u_count.
+	 * in the directory.  To use this space, we may have to compact
+	 * the entries located there, by copying them together towards
+	 * the beginning of the block, leaving the free space in
+	 * one usable chunk at the end.
+	 */
+
+	/*
+	 * Increase size of directory if entry eats into new space.
+	 * This should never push the size past a new multiple of
+	 * DIRBLKSIZE.
+	 */
+	if (u.u_offset + u.u_count > u.u_pdir->i_size)
+		u.u_pdir->i_size = u.u_offset + u.u_count;
+
+	/*
+	 * Get the block containing the space for the new directory
+	 * entry.
+	 */
+	bp = blkatoff(u.u_pdir, u.u_offset, (char **)&dirbuf);
+	if (bp == 0) {
+		iput(u.u_pdir);
+		return;
 	}
 
 	/*
-	 * Here a component matched in a directory.
-	 * If there is more pathname, go back to
-	 * cloop, otherwise return.
+	 * Find space for the new entry.  In the simple case, the
+	 * entry at offset base will have the space.  If it does
+	 * not, then namei arranged that compacting the region
+	 * u.u_offset to u.u_offset+u.u_count would yield the space.
 	 */
-	bcopy((caddr_t)ep, (caddr_t)&u.u_dent, sizeof(struct direct));
-	if(bp != NULL)
-		brelse(bp);
-	if(flag==2 && c=='\0') {
-		if(access(dp, IWRITE))
-			goto out;
-		return(dp);
-	}
-	d = dp->i_dev;
-	if(u.u_dent.d_ino == ROOTINO)
-	if(dp->i_number == ROOTINO)
-	if(u.u_dent.d_name[1] == '.')
-		for(i=1; i<NMOUNT; i++)
-			if(mount[i].m_bufp != NULL)
-			if(mount[i].m_dev == d) {
-				iput(dp);
-				dp = mount[i].m_inodp;
-				dp->i_count++;
-				plock(dp);
-				goto seloop;
-			}
-	iput(dp);
-	dp = iget(d, u.u_dent.d_ino);
-	if(dp == NULL)
-		return(NULL);
-	goto cloop;
+	ep = (struct direct *)dirbuf;
+	dsize = DIRSIZ(ep);
+	freespace = ep->d_reclen - dsize;
+	for (loc = ep->d_reclen; loc < u.u_count; ) {
+		nep = (struct direct *)(dirbuf + loc);
+		if (ep->d_ino) {
+			/* trim the existing slot */
+			ep->d_reclen = dsize;
+			ep = (struct direct *)((char *)ep + dsize);
+		} else {
+			/* overwrite; nothing there; header is ours */
+			freespace += dsize;	
+		}
+		dsize = DIRSIZ(nep);
+		freespace += nep->d_reclen - dsize;
+		loc += nep->d_reclen;
+		bcopy((caddr_t)nep, (caddr_t)ep, dsize);
+	}
+	/*
+	 * Update the pointer fields in the previous entry (if any),
+	 * copy in the new entry, and write out the block.
+	 */
+	if (ep->d_ino == 0) {
+		if (freespace + dsize < newentrysize)
+			panic("wdir: compact1");
+		u.u_dent.d_reclen = freespace + dsize;
+	} else {
+		if (freespace < newentrysize)
+			panic("wdir: compact2");
+		u.u_dent.d_reclen = freespace;
+		ep->d_reclen = dsize;
+		ep = (struct direct *)((char *)ep + dsize);
+	}
+	bcopy((caddr_t)&u.u_dent, (caddr_t)ep, (u_int)newentrysize);
+	bwrite(bp);
+	u.u_pdir->i_flag |= IUPD|ICHG;
+	iput(u.u_pdir);
+}
+
+/*
+ * Remove a directory entry after a call to namei, using the
+ * parameters which it left in the u. area.  The u. entry
+ * u_offset contains the offset into the directory of the
+ * entry to be eliminated.  The u_count field contains the
+ * size of the previous record in the directory.  If this
+ * is 0, the first entry is being deleted, so we need only
+ * zero the inode number to mark the entry as free.  If the
+ * entry isn't the first in the directory, we must reclaim
+ * the space of the now empty record by adding the record size
+ * to the size of the previous entry.
+ */
+dirremove()
+{
+	register struct inode *dp = u.u_pdir;
+	register struct buf *bp;
+	struct direct *ep;
+
+	if (u.u_count == 0) {
+		/*
+		 * First entry in block: set d_ino to zero.
+		 */
+		u.u_dent.d_ino = 0;
+		(void) rdwri(UIO_WRITE, dp, (caddr_t)&u.u_dent,
+		    (int)DIRSIZ(&u.u_dent), u.u_offset, 1, (int *)0);
+	} else {
+		/*
+		 * Collapse new free space into previous entry.
+		 */
+		bp = blkatoff(dp, (int)(u.u_offset - u.u_count), (char **)&ep);
+		if (bp == 0)
+			return (0);
+		ep->d_reclen += u.u_dent.d_reclen;
+		bwrite(bp);
+		dp->i_flag |= IUPD|ICHG;
+	}
+	return (1);
+}
+
+/*
+ * Rewrite an existing directory entry to point at the inode
+ * supplied.  The parameters describing the directory entry are
+ * set up by a call to namei.
+ */
+dirrewrite(dp, ip)
+	struct inode *dp, *ip;
+{
 
-out:
+	u.u_dent.d_ino = ip->i_number;
+	u.u_error = rdwri(UIO_WRITE, dp, (caddr_t)&u.u_dent,
+		(int)DIRSIZ(&u.u_dent), u.u_offset, 1, (int *)0);
 	iput(dp);
-	return(NULL);
 }
 
 /*
- * Return the next character from the
- * kernel string pointed at by dirp.
+ * Return buffer with contents of block "offset"
+ * from the beginning of directory "ip".  If "res"
+ * is non-zero, fill it in with a pointer to the
+ * remaining space in the directory.
  */
-schar()
+struct buf *
+blkatoff(ip, offset, res)
+	struct inode *ip;
+	off_t offset;
+	char **res;
 {
+	register struct fs *fs = ip->i_fs;
+	daddr_t lbn = lblkno(fs, offset);
+	int base = blkoff(fs, offset);
+	int bsize = blksize(fs, ip, lbn);
+	daddr_t bn = fsbtodb(fs, bmap(ip, lbn, B_WRITE, base, bsize));
+	register struct buf *bp;
 
-	return(*u.u_dirp++ & 0377);
+	if (u.u_error)
+		return (0);
+	bp = bread(ip->i_dev, bn, bsize);
+	if (bp->b_flags & B_ERROR) {
+		brelse(bp);
+		return (0);
+	}
+	if (res)
+		*res = bp->b_un.b_addr + base;
+	return (bp);
 }
 
 /*
- * Return the next character from the
- * user string pointed at by dirp.
+ * Check if a directory is empty or not.
+ * Inode supplied must be locked.
  */
-uchar()
+dirempty(ip)
+	register struct inode *ip;
 {
-	register c;
+	register off_t off;
+	struct direct dbuf;
+	register struct direct *dp = &dbuf;
+	int error, count;
 
-	c = fubyte(u.u_dirp++);
-	if(c == -1)
-		u.u_error = EFAULT;
-	return(c);
+	for (off = 0; off < ip->i_size; off += dp->d_reclen) {
+		error = rdwri(UIO_READ, ip, (caddr_t)dp,
+			sizeof (struct direct), off, 1, &count);
+		count = sizeof (struct direct) - count;
+#define	MINDIRSIZ (sizeof (struct direct) - (MAXNAMLEN + 1))
+		if (error || count < MINDIRSIZ || count < DIRSIZ(dp))
+			return (0);
+		if (dp->d_ino == 0)
+			continue;
+		if (dp->d_name[0] != '.')
+			return (0);
+		if (dp->d_namlen == 1 ||
+		    (dp->d_namlen == 2 && dp->d_name[1] == '.'))
+			continue;
+		return (0);
+	}
+	return (1);
 }