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>

fs/ext3/super.c

@@ -2758,12 +2758,12 @@ static int ext3_quota_on(struct super_block *sb, int type, int format_id,
 	if (err)
 		return err;
 	/* Quotafile not on the same filesystem? */
-	if (nd.mnt->mnt_sb != sb) {
+	if (nd.path.mnt->mnt_sb != sb) {
 		path_release(&nd);
 		return -EXDEV;
 	}
 	/* Quotafile not of fs root? */
-	if (nd.dentry->d_parent->d_inode != sb->s_root->d_inode)
+	if (nd.path.dentry->d_parent->d_inode != sb->s_root->d_inode)
 		printk(KERN_WARNING
 			"EXT3-fs: Quota file not on filesystem root. "
 			"Journalled quota will not work.\n");