follow_automount() doesn't need the entire nameidata

Only the address of ->total_link_count and the flags.
And fix an off-by-one is ELOOP detection - make it
consistent with symlink following, where we check if
the pre-increment value has reached 40, rather than
check the post-increment one.

[kudos to Christian Brauner for spotted braino]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -1208,7 +1208,7 @@ EXPORT_SYMBOL(follow_up);
  * - return -EISDIR to tell follow_managed() to stop and return the path we
  *   were called with.
  */
-static int follow_automount(struct path *path, struct nameidata *nd)
+static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
 {
 	struct dentry *dentry = path->dentry;
 
@@ -1223,13 +1223,12 @@ static int follow_automount(struct path *path, struct nameidata *nd)
 	 * as being automount points.  These will need the attentions
 	 * of the daemon to instantiate them before they can be used.
 	 */
-	if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
+	if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
 			   LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
 	    dentry->d_inode)
 		return -EISDIR;
 
-	nd->total_link_count++;
-	if (nd->total_link_count >= 40)
+	if (count && (*count)++ >= MAXSYMLINKS)
 		return -ELOOP;
 
 	return finish_automount(dentry->d_op->d_automount(path), path);
@@ -1290,7 +1289,8 @@ static int follow_managed(struct path *path, struct nameidata *nd)
 
 		/* Handle an automount point */
 		if (flags & DCACHE_NEED_AUTOMOUNT) {
-			ret = follow_automount(path, nd);
+			ret = follow_automount(path, &nd->total_link_count,
+						nd->flags);
 			if (ret < 0)
 				break;
 			continue;