speed-ups using the new constants
[unix-history] / usr / src / sys / kern / vfs_lookup.c
index 7cb0879..d42e012 100644 (file)
-/*     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/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/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 *
  */
 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;
        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;
                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;
 
        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);
        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);
 }
 }