3 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index c422367baed9..2327859c8cd2 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -237,4 +237,32 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
 	return 0;
 }
 
+/**
+ * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
+ * @dir: directory being searched
+ * @dentry: filename being looked up
+ * @flags: lookup flags
+ *
+ * Prepare for ->lookup() in a directory which may be encrypted.  Lookups can be
+ * done with or without the directory's encryption key; without the key,
+ * filenames are presented in encrypted form.  Therefore, we'll try to set up
+ * the directory's encryption key, but even without it the lookup can continue.
+ *
+ * To allow invalidating stale dentries if the directory's encryption key is
+ * added later, we also install a custom ->d_revalidate() method and use the
+ * DCACHE_ENCRYPTED_WITH_KEY flag to indicate whether a given dentry is a
+ * plaintext name (flag set) or a ciphertext name (flag cleared).
+ *
+ * Return: 0 on success, -errno if a problem occurred while setting up the
+ * encryption key
+ */
+static inline int fscrypt_prepare_lookup(struct inode *dir,
+					 struct dentry *dentry,
+					 unsigned int flags)
+{
+	if (IS_ENCRYPTED(dir))
+		return __fscrypt_prepare_lookup(dir, dentry);
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_H */
diff --git a/include/linux/fscrypt_notsupp.h b/include/linux/fscrypt_notsupp.h
index 6af378d8126e..c4c6bf2c390e 100644
--- a/include/linux/fscrypt_notsupp.h
+++ b/include/linux/fscrypt_notsupp.h
@@ -201,4 +201,10 @@ static inline int __fscrypt_prepare_rename(struct inode *old_dir,
 	return -EOPNOTSUPP;
 }
 
+static inline int __fscrypt_prepare_lookup(struct inode *dir,
+					   struct dentry *dentry)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */
diff --git a/include/linux/fscrypt_supp.h b/include/linux/fscrypt_supp.h
index 40f35073145f..2db5e9706f60 100644
--- a/include/linux/fscrypt_supp.h
+++ b/include/linux/fscrypt_supp.h
@@ -151,5 +151,6 @@ extern int __fscrypt_prepare_rename(struct inode *old_dir,
 				    struct inode *new_dir,
 				    struct dentry *new_dentry,
 				    unsigned int flags);
+extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
 
 #endif	/* _LINUX_FSCRYPT_SUPP_H */