more on vfs-scale and vfs-automount

index 0087cf9..a0f2179 100644
@@ -1022,6 +1022,14 @@ int follow_down_one(struct path *path)
 	return 0;
 }
 
+static bool managed_dentry_might_block(struct dentry *dentry)
+{
+	if (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
+	    dentry->d_op->d_manage(dentry, false, true) < 0)
+		return true;
+	return false;
+}
+
 /*
  * Skip to top of mountpoint pile in rcuwalk mode.  We abort the rcu-walk if we
  * meet a managed dentry and we're not walking to "..".  True is returned to

@@ -1030,12 +1038,17 @@ int follow_down_one(struct path *path)
 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
 			       struct inode **inode, bool reverse_transit)
 {
+	/*
+	 * Don't forgat we might have a non-mountpoint managed dentry
+	 * that wants to block transit.
+	 */
+	*inode = path->dentry->d_inode;
+	if (!reverse_transit &&
+	     unlikely(managed_dentry_might_block(path->dentry)))
+		return false;
+
 	while (d_mountpoint(path->dentry)) {
 		struct vfsmount *mounted;
-		if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
-		    !reverse_transit &&
-		    path->dentry->d_op->d_manage(path->dentry, false, true) < 0)
-			return false;
 		mounted = __lookup_mnt(path->mnt, path->dentry, 1);
 		if (!mounted)
 			break;

@@ -1043,6 +1056,9 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
 		path->dentry = mounted->mnt_root;
 		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
 		*inode = path->dentry->d_inode;
+		if (!reverse_transit &&
+		    unlikely(managed_dentry_might_block(path->dentry)))
+			return false;
 	}
 
 	if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))

index f43100b..c896dd6 100644
@@ -294,7 +294,6 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
 		spin_unlock(&sbi->fs_lock);
 		return NULL;
 	}
-	managed_dentry_set_transit(root);
 	if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 		struct autofs_info *ino = autofs4_dentry_ino(root);
 		ino->flags |= AUTOFS_INF_EXPIRING;

@@ -302,7 +301,6 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
 		spin_unlock(&sbi->fs_lock);
 		return root;
 	}
-	managed_dentry_clear_transit(root);
 	spin_unlock(&sbi->fs_lock);
 	dput(root);
 

@@ -341,8 +339,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 		ino = autofs4_dentry_ino(dentry);
 		/* No point expiring a pending mount */
 		if (ino->flags & AUTOFS_INF_PENDING)
-			goto cont;
-		managed_dentry_set_transit(dentry);
+			goto next;
 
 		/*
 		 * Case 1: (i) indirect mount or top level pseudo direct mount

@@ -402,8 +399,6 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 			}
 		}
 next:
-		managed_dentry_clear_transit(dentry);
-cont:
 		spin_unlock(&sbi->fs_lock);
 	}
 	return NULL;

@@ -484,8 +479,6 @@ int autofs4_expire_run(struct super_block *sb,
 	spin_lock(&sbi->fs_lock);
 	ino = autofs4_dentry_ino(dentry);
 	ino->flags &= ~AUTOFS_INF_EXPIRING;
-	if (!d_unhashed(dentry))
-		managed_dentry_clear_transit(dentry);
 	complete_all(&ino->expire_complete);
 	spin_unlock(&sbi->fs_lock);
 

@@ -513,9 +506,7 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 		spin_lock(&sbi->fs_lock);
 		ino->flags &= ~AUTOFS_INF_EXPIRING;
 		spin_lock(&dentry->d_lock);
-		if (ret)
-			__managed_dentry_clear_transit(dentry);
-		else {
+		if (!ret) {
 			if ((IS_ROOT(dentry) ||
 			    (autofs_type_indirect(sbi->type) &&
 			     IS_ROOT(dentry->d_parent))) &&

index 014e7ab..ad11a44 100644
@@ -338,18 +338,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 	DPRINTK("dentry=%p %.*s",
 		dentry, dentry->d_name.len, dentry->d_name.name);
 
-	/*
-	 * Someone may have manually umounted this or it was a submount
-	 * that has gone away.
-	 */
-	spin_lock(&dentry->d_lock);
-	if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
-		if (!(dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
-		     (dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
-			__managed_dentry_set_transit(path->dentry);
-	}
-	spin_unlock(&dentry->d_lock);
-
 	/* The daemon never triggers a mount. */
 	if (autofs4_oz_mode(sbi))
 		return NULL;

@@ -418,12 +406,12 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 done:
 	if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
 		/*
-		 * Any needed mounting has been completed and the path updated
-		 * so turn this into a normal dentry so we don't continually
-		 * call ->d_automount() and ->d_manage().
+		 * Any needed mounting has been completed and the path
+		 * updated so clear DCACHE_NEED_AUTOMOUNT so we don't
+		 * call ->d_automount() on rootless multi-mounts since
+		 * it can lead to an incorrect ELOOP error return.
 		 */
 		spin_lock(&dentry->d_lock);
-		__managed_dentry_clear_transit(dentry);
 		/*
 		 * Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and
 		 * symlinks as in all other cases the dentry will be covered by

index c896dd6..c403abc 100644
@@ -290,10 +290,8 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
 	spin_lock(&sbi->fs_lock);
 	ino = autofs4_dentry_ino(root);
 	/* No point expiring a pending mount */
-	if (ino->flags & AUTOFS_INF_PENDING) {
-		spin_unlock(&sbi->fs_lock);
-		return NULL;
-	}
+	if (ino->flags & AUTOFS_INF_PENDING)
+		goto out;
 	if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 		struct autofs_info *ino = autofs4_dentry_ino(root);
 		ino->flags |= AUTOFS_INF_EXPIRING;

@@ -301,6 +299,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
 		spin_unlock(&sbi->fs_lock);
 		return root;
 	}
+out:
 	spin_unlock(&sbi->fs_lock);
 	dput(root);
 

index c403abc..bc482e0 100644
@@ -87,6 +87,56 @@ done:
 }
 
 /*
+ * Calculate and dget next entry in the subdirs list under root.
+ */
+static struct dentry *get_next_positive_subdir(struct dentry *prev,
+						struct dentry *root)
+{
+	struct list_head *next;
+	struct dentry *p, *q;
+
+	spin_lock(&autofs4_lock);
+
+	if (prev == NULL) {
+		spin_lock(&root->d_lock);
+		prev = dget_dlock(root);
+		next = prev->d_subdirs.next;
+		p = prev;
+		goto start;
+	}
+
+	p = prev;
+	spin_lock(&p->d_lock);
+again:
+	next = p->d_u.d_child.next;
+start:
+	if (next == &root->d_subdirs) {
+		spin_unlock(&p->d_lock);
+		spin_unlock(&autofs4_lock);
+		dput(prev);
+		return NULL;
+	}
+
+	q = list_entry(next, struct dentry, d_u.d_child);
+
+	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
+	/* Negative dentry - try next */
+	if (!simple_positive(q)) {
+		spin_unlock(&p->d_lock);
+		p = q;
+		goto again;
+	}
+	dget_dlock(q);
+	spin_unlock(&q->d_lock);
+	spin_unlock(&p->d_lock);
+	spin_unlock(&autofs4_lock);
+
+	dput(prev);
+
+	return q;
+}
+
+/*
  * Calculate and dget next entry in top down tree traversal.
  */
 static struct dentry *get_next_positive_dentry(struct dentry *prev,

@@ -333,7 +383,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 	timeout = sbi->exp_timeout;
 
 	dentry = NULL;
-	while ((dentry = get_next_positive_dentry(dentry, root))) {
+	while ((dentry = get_next_positive_subdir(dentry, root))) {
 		spin_lock(&sbi->fs_lock);
 		ino = autofs4_dentry_ino(dentry);
 		/* No point expiring a pending mount */