fscrypt: add comment for fscrypt_valid_enc_modes_v1()

Make it clear that nothing new should be added to this function.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221125192047.18916-1-ebiggers@kernel.org

fs/crypto/policy.c

@@ -61,6 +61,13 @@ fscrypt_get_dummy_policy(struct super_block *sb)
 	return sb->s_cop->get_dummy_policy(sb);
 }
 
+/*
+ * Return %true if the given combination of encryption modes is supported for v1
+ * (and later) encryption policies.
+ *
+ * Do *not* add anything new here, since v1 encryption policies are deprecated.
+ * New combinations of modes should go in fscrypt_valid_enc_modes_v2() only.
+ */
 static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode)
 {
 	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&