[PATCH] fscrypt: introduce fscrypt_needs_contents_encryption()

[Eric Biggers <ebiggers@kernel.org>]

From: Eric Biggers <ebiggers@google.com>

Add a function fscrypt_needs_contents_encryption() which takes an inode
and returns true if it's an encrypted regular file and the kernel was
built with fscrypt support.

This will allow replacing duplicated checks of IS_ENCRYPTED() &&
S_ISREG() on the I/O paths in ext4 and f2fs, while also optimizing out
unneeded code when !CONFIG_FS_ENCRYPTION.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/linux/fscrypt.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index cb18b5fbcef92..2a29f56b1a1cb 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -72,6 +72,21 @@ static inline bool fscrypt_has_encryption_key(const struct inode *inode)
 	return READ_ONCE(inode->i_crypt_info) != NULL;
 }
 
+/**
+ * fscrypt_needs_contents_encryption() - check whether an inode needs
+ *					 contents encryption
+ *
+ * Return: %true iff the inode is an encrypted regular file and the kernel was
+ * built with fscrypt support.
+ *
+ * If you need to know whether the encrypt bit is set even when the kernel was
+ * built without fscrypt support, you must use IS_ENCRYPTED() directly instead.
+ */
+static inline bool fscrypt_needs_contents_encryption(const struct inode *inode)
+{
+	return IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode);
+}
+
 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
 {
 	return inode->i_sb->s_cop->dummy_context &&
@@ -269,6 +284,11 @@ static inline bool fscrypt_has_encryption_key(const struct inode *inode)
 	return false;
 }
 
+static inline bool fscrypt_needs_contents_encryption(const struct inode *inode)
+{
+	return false;
+}
+
 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
 {
 	return false;
-- 
2.24.0.393.g34dc348eaf-goog