1 files changed, 48 insertions, 0 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b48273e846ad..f7eba21effa5 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -777,6 +777,54 @@ struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
 	return inode;
 }
 
+bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+	struct inode *key = d_inode(dir);
+	struct inode *trap;
+	bool res;
+
+	trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
+	if (!trap)
+		return false;
+
+	res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
+				  !ovl_inode_lower(trap);
+
+	iput(trap);
+	return res;
+}
+
+/*
+ * Create an inode cache entry for layer root dir, that will intentionally
+ * fail ovl_verify_inode(), so any lookup that will find some layer root
+ * will fail.
+ */
+struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+	struct inode *key = d_inode(dir);
+	struct inode *trap;
+
+	if (!d_is_dir(dir))
+		return ERR_PTR(-ENOTDIR);
+
+	trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
+			    ovl_inode_set, key);
+	if (!trap)
+		return ERR_PTR(-ENOMEM);
+
+	if (!(trap->i_state & I_NEW)) {
+		/* Conflicting layer roots? */
+		iput(trap);
+		return ERR_PTR(-ELOOP);
+	}
+
+	trap->i_mode = S_IFDIR;
+	trap->i_flags = S_DEAD;
+	unlock_new_inode(trap);
+
+	return trap;
+}
+
 /*
  * Does overlay inode need to be hashed by lower inode?
  */