On Sun, Apr 06, 2025 at 09:43:02PM +0100, Tingmao Wang wrote:

+struct v9fs_ino_path *make_ino_path(struct dentry *dentry)
+{
+	struct v9fs_ino_path *path;
+	size_t path_components = 0;
+	struct dentry *curr = dentry;
+	ssize_t i;
+
+	lockdep_assert_held_read(&v9fs_dentry2v9ses(dentry)->rename_sem);
+
+	rcu_read_lock();
+
+    /* Don't include the root dentry */
+	while (curr->d_parent != curr) {
+		path_components++;
+		curr = curr->d_parent;
+	}
+	if (WARN_ON(path_components > SSIZE_MAX)) {
+		rcu_read_unlock();
+		return NULL;
+	}
+
+	path = kmalloc(struct_size(path, names, path_components),
+		       GFP_KERNEL);

Blocking allocation under rcu_read_lock().