Embed a struct path into struct nameidata instead of nd->{dentry,mnt}

This is the central patch of a cleanup series. In most cases there is no good
reason why someone would want to use a dentry for itself. This series reflects
that fact and embeds a struct path into nameidata.

Together with the other patches of this series
- it enforced the correct order of getting/releasing the reference count on
  <dentry,vfsmount> pairs
- it prepares the VFS for stacking support since it is essential to have a
  struct path in every place where the stack can be traversed
- it reduces the overall code size:

without patch series:
   text    data     bss     dec     hex filename
5321639  858418  715768 6895825  6938d1 vmlinux

with patch series:
   text    data     bss     dec     hex filename
5320026  858418  715768 6894212  693284 vmlinux

This patch:

Switch from nd->{dentry,mnt} to nd->path.{dentry,mnt} everywhere.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix cifs]
[akpm@linux-foundation.org: fix smack]
Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
index 9b430f2..e376f45 100644
--- a/drivers/mtd/mtdsuper.c
+++ b/drivers/mtd/mtdsuper.c
@@ -184,25 +184,25 @@
 	ret = path_lookup(dev_name, LOOKUP_FOLLOW, &nd);
 
 	DEBUG(1, "MTDSB: path_lookup() returned %d, inode %p\n",
-	      ret, nd.dentry ? nd.dentry->d_inode : NULL);
+	      ret, nd.path.dentry ? nd.path.dentry->d_inode : NULL);
 
 	if (ret)
 		return ret;
 
 	ret = -EINVAL;
 
-	if (!S_ISBLK(nd.dentry->d_inode->i_mode))
+	if (!S_ISBLK(nd.path.dentry->d_inode->i_mode))
 		goto out;
 
-	if (nd.mnt->mnt_flags & MNT_NODEV) {
+	if (nd.path.mnt->mnt_flags & MNT_NODEV) {
 		ret = -EACCES;
 		goto out;
 	}
 
-	if (imajor(nd.dentry->d_inode) != MTD_BLOCK_MAJOR)
+	if (imajor(nd.path.dentry->d_inode) != MTD_BLOCK_MAJOR)
 		goto not_an_MTD_device;
 
-	mtdnr = iminor(nd.dentry->d_inode);
+	mtdnr = iminor(nd.path.dentry->d_inode);
 	path_release(&nd);
 
 	return get_sb_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super,