block: blk-crypto-fallback for Inline Encryption

Blk-crypto delegates crypto operations to inline encryption hardware
when available. The separately configurable blk-crypto-fallback contains
a software fallback to the kernel crypto API - when enabled, blk-crypto
will use this fallback for en/decryption when inline encryption hardware
is not available.

This lets upper layers not have to worry about whether or not the
underlying device has support for inline encryption before deciding to
specify an encryption context for a bio. It also allows for testing
without actual inline encryption hardware - in particular, it makes it
possible to test the inline encryption code in ext4 and f2fs simply by
running xfstests with the inlinecrypt mount option, which in turn allows
for things like the regular upstream regression testing of ext4 to cover
the inline encryption code paths.

For more details, refer to Documentation/block/inline-encryption.rst.

Signed-off-by: Satya Tangirala <satyat@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 35 insertions, 0 deletions

diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index 796f757fe8e9..d2b0f565d83c 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -11,10 +11,13 @@
 
 /* Represents a crypto mode supported by blk-crypto  */
 struct blk_crypto_mode {
+	const char *cipher_str; /* crypto API name (for fallback case) */
 	unsigned int keysize; /* key size in bytes */
 	unsigned int ivsize; /* iv size in bytes */
 };
 
+extern const struct blk_crypto_mode blk_crypto_modes[];
+
 #ifdef CONFIG_BLK_INLINE_ENCRYPTION
 
 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
@@ -163,4 +166,36 @@ static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq)
 	return BLK_STS_OK;
 }
 
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK
+
+int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num);
+
+bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr);
+
+int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key);
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK */
+
+static inline int
+blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
+{
+	pr_warn_once("crypto API fallback is disabled\n");
+	return -ENOPKG;
+}
+
+static inline bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
+{
+	pr_warn_once("crypto API fallback disabled; failing request.\n");
+	(*bio_ptr)->bi_status = BLK_STS_NOTSUPP;
+	return false;
+}
+
+static inline int
+blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
+{
+	return 0;
+}
+
+#endif /* CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK */
+
 #endif /* __LINUX_BLK_CRYPTO_INTERNAL_H */