fscrypt: move fscrypt_require_key() to fscrypt_private.h

fscrypt_require_key() is now only used by files in fs/crypto/.  So
reduce its visibility to fscrypt_private.h.  This is also a prerequsite
for unexporting fscrypt_get_encryption_info().

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201203022041.230976-8-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index a61d4dbf0a0b..16dd55080127 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -571,6 +571,32 @@ int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
 void fscrypt_hash_inode_number(struct fscrypt_info *ci,
 			       const struct fscrypt_master_key *mk);
 
+/**
+ * fscrypt_require_key() - require an inode's encryption key
+ * @inode: the inode we need the key for
+ *
+ * If the inode is encrypted, set up its encryption key if not already done.
+ * Then require that the key be present and return -ENOKEY otherwise.
+ *
+ * No locks are needed, and the key will live as long as the struct inode --- so
+ * it won't go away from under you.
+ *
+ * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
+ * if a problem occurred while setting up the encryption key.
+ */
+static inline int fscrypt_require_key(struct inode *inode)
+{
+	if (IS_ENCRYPTED(inode)) {
+		int err = fscrypt_get_encryption_info(inode);
+
+		if (err)
+			return err;
+		if (!fscrypt_has_encryption_key(inode))
+			return -ENOKEY;
+	}
+	return 0;
+}
+
 /* keysetup_v1.c */
 
 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);