diff --git a/fs/mount.h b/fs/mount.h
index e0816c11a198..5df134d56d47 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -25,6 +25,7 @@ struct mnt_namespace {
 	__u32			n_fsnotify_mask;
 	struct fsnotify_mark_connector __rcu *n_fsnotify_marks;
 #endif
+	struct hlist_head	mnt_visible_mounts; /* SB_I_USERNS_VISIBLE mounts */
 	unsigned int		nr_mounts; /* # of mounts in the namespace */
 	unsigned int		pending_mounts;
 	refcount_t		passive; /* number references not pinning @mounts */
@@ -90,6 +91,7 @@ struct mount {
 	int mnt_expiry_mark;		/* true if marked for expiry */
 	struct hlist_head mnt_pins;
 	struct hlist_head mnt_stuck_children;
+	struct hlist_node mnt_ns_visible; /* link in ns->mnt_visible_mounts */
 	struct mount *overmount;	/* mounted on ->mnt_root */
 } __randomize_layout;
 
@@ -207,6 +209,8 @@ static inline void move_from_ns(struct mount *mnt)
 		ns->mnt_first_node = rb_next(&mnt->mnt_node);
 	rb_erase(&mnt->mnt_node, &ns->mounts);
 	RB_CLEAR_NODE(&mnt->mnt_node);
+	if (!hlist_unhashed(&mnt->mnt_ns_visible))
+		hlist_del_init(&mnt->mnt_ns_visible);
 }
 
 bool has_locked_children(struct mount *mnt, struct dentry *dentry);
diff --git a/fs/namespace.c b/fs/namespace.c
index fe919abd2f01..047efa737ef9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -321,6 +321,7 @@ static struct mount *alloc_vfsmnt(const char *name)
 		INIT_HLIST_NODE(&mnt->mnt_slave);
 		INIT_HLIST_NODE(&mnt->mnt_mp_list);
 		INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
+		INIT_HLIST_NODE(&mnt->mnt_ns_visible);
 		RB_CLEAR_NODE(&mnt->mnt_node);
 		mnt->mnt.mnt_idmap = &nop_mnt_idmap;
 	}
@@ -1098,6 +1099,10 @@ static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
 	rb_link_node(&mnt->mnt_node, parent, link);
 	rb_insert_color(&mnt->mnt_node, &ns->mounts);
 
+	if ((mnt->mnt.mnt_sb->s_iflags & SB_I_USERNS_VISIBLE) &&
+	    mnt->mnt.mnt_root == mnt->mnt.mnt_sb->s_root)
+		hlist_add_head(&mnt->mnt_ns_visible, &ns->mnt_visible_mounts);
+
 	mnt_notify_add(mnt);
 }
 
@@ -6340,22 +6345,20 @@ static bool mnt_already_visible(struct mnt_namespace *ns,
 				int *new_mnt_flags)
 {
 	int new_flags = *new_mnt_flags;
-	struct mount *mnt, *n;
+	struct mount *mnt;
+
+	/* Don't acquire namespace semaphore without a good reason. */
+	if (hlist_empty(&ns->mnt_visible_mounts))
+		return false;
 
 	guard(namespace_shared)();
-	rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
+	hlist_for_each_entry(mnt, &ns->mnt_visible_mounts, mnt_ns_visible) {
 		struct mount *child;
 		int mnt_flags;
 
 		if (mnt->mnt.mnt_sb->s_type != sb->s_type)
 			continue;
 
-		/* This mount is not fully visible if it's root directory
-		 * is not the root directory of the filesystem.
-		 */
-		if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
-			continue;
-
 		/* A local view of the mount flags */
 		mnt_flags = mnt->mnt.mnt_flags;