FROMLIST: block: blk-crypto for Inline Encryption

We introduce blk-crypto, which manages programming keyslots for struct
bios. With blk-crypto, filesystems only need to call bio_crypt_set_ctx with
the encryption key, algorithm and data_unit_num; they don't have to worry
about getting a keyslot for each encryption context, as blk-crypto handles
that. Blk-crypto also makes it possible for layered devices like device
mapper to make use of inline encryption hardware.

Blk-crypto delegates crypto operations to inline encryption hardware when
available, and also contains a software fallback to the kernel crypto API.
For more details, refer to Documentation/block/inline-encryption.rst.

Bug: 137270441
Test: tested as series; see Ie1b77f7615d6a7a60fdc9105c7ab2200d17636a8
Change-Id: I7df59fef0c1e90043b1899c5a95973e23afac0c5
Signed-off-by: Satya Tangirala <satyat@google.com>
Link: https://patchwork.kernel.org/patch/11214731/

include/linux/blk-crypto.h

@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef __LINUX_BLK_CRYPTO_H
+#define __LINUX_BLK_CRYPTO_H
+
+#include <linux/types.h>
+#include <linux/bio.h>
+
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+int blk_crypto_init(void);
+
+int blk_crypto_submit_bio(struct bio **bio_ptr);
+
+bool blk_crypto_endio(struct bio *bio);
+
+int blk_crypto_start_using_mode(enum blk_crypto_mode_num mode_num,
+				unsigned int data_unit_size,
+				struct request_queue *q);
+
+int blk_crypto_evict_key(struct request_queue *q, const u8 *key,
+			 enum blk_crypto_mode_num mode,
+			 unsigned int data_unit_size);
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline int blk_crypto_init(void)
+{
+	return 0;
+}
+
+static inline int blk_crypto_submit_bio(struct bio **bio_ptr)
+{
+	return 0;
+}
+
+static inline bool blk_crypto_endio(struct bio *bio)
+{
+	return true;
+}
+
+static inline int
+blk_crypto_start_using_mode(enum blk_crypto_mode_num mode_num,
+			    unsigned int data_unit_size,
+			    struct request_queue *q)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int blk_crypto_evict_key(struct request_queue *q, const u8 *key,
+				       enum blk_crypto_mode_num mode,
+				       unsigned int data_unit_size)
+{
+	return 0;
+}
+
+#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+#endif /* __LINUX_BLK_CRYPTO_H */