fs/tunnel.c

   1 /*  fs/tunnel.c: utility functions to support VFS tunnelling
   2
   3     Copyright (C) 1999  Richard Gooch
   4
   5     This library is free software; you can redistribute it and/or
   6     modify it under the terms of the GNU Library General Public
   7     License as published by the Free Software Foundation; either
   8     version 2 of the License, or (at your option) any later version.
   9
  10     This library is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13     Library General Public License for more details.
  14
  15     You should have received a copy of the GNU Library General Public
  16     License along with this library; if not, write to the Free
  17     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18
  19     Richard Gooch may be reached by email at  rgooch@atnf.csiro.au
  20     The postal address is:
  21       Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
  22
  23     ChangeLog
  24
  25     19991121   Richard Gooch <rgooch@atnf.csiro.au>
  26                Created.
  27 */
  28 #include <linux/types.h>
  29 #include <linux/errno.h>
  30 #include <linux/ctype.h>
  31 #include <linux/module.h>
  32 #include <linux/fs.h>
  33
  34
  35 /*PUBLIC_FUNCTION*/
  36 struct dentry *vfs_tunnel_lookup (const struct dentry *dentry,
  37                                   const struct dentry *parent,
  38                                   const struct dentry *covered)
  39 /*  [SUMMARY] Lookup the corresponding dentry in the mounted-over FS.
  40     <dentry> The dentry which is in the overmounting FS.
  41     <parent> The parent of the dentry in the mounted-over FS. This may be NULL.
  42     <covered> The dentry covered by the root dentry of the overmounting FS.
  43     [RETURNS] A dentry on success, else NULL.
  44 */
  45 {
  46     struct dentry *root = dentry->d_sb->s_root;
  47
  48     if (covered == root) return NULL;
  49     if (parent) return lookup_dentry (dentry->d_name.name, parent, 0);
  50 }   /*  End Function vfs_tunnel_lookup  */