block: Inline encryption support for blk-mq

We must have some way of letting a storage device driver know what
encryption context it should use for en/decrypting a request. However,
it's the upper layers (like the filesystem/fscrypt) that know about and
manages encryption contexts. As such, when the upper layer submits a bio
to the block layer, and this bio eventually reaches a device driver with
support for inline encryption, the device driver will need to have been
told the encryption context for that bio.

We want to communicate the encryption context from the upper layer to the
storage device along with the bio, when the bio is submitted to the block
layer. To do this, we add a struct bio_crypt_ctx to struct bio, which can
represent an encryption context (note that we can't use the bi_private
field in struct bio to do this because that field does not function to pass
information across layers in the storage stack). We also introduce various
functions to manipulate the bio_crypt_ctx and make the bio/request merging
logic aware of the bio_crypt_ctx.

We also make changes to blk-mq to make it handle bios with encryption
contexts. blk-mq can merge many bios into the same request. These bios need
to have contiguous data unit numbers (the necessary changes to blk-merge
are also made to ensure this) - as such, it suffices to keep the data unit
number of just the first bio, since that's all a storage driver needs to
infer the data unit number to use for each data block in each bio in a
request. blk-mq keeps track of the encryption context to be used for all
the bios in a request with the request's rq_crypt_ctx. When the first bio
is added to an empty request, blk-mq will program the encryption context
of that bio into the request_queue's keyslot manager, and store the
returned keyslot in the request's rq_crypt_ctx. All the functions to
operate on encryption contexts are in blk-crypto.c.

Upper layers 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-mq/blk-crypto handles that.
Blk-crypto also makes it possible for request-based layered devices like
dm-rq to make use of inline encryption hardware by cloning the
rq_crypt_ctx and programming a keyslot in the new request_queue when
necessary.

Note that any user of the block layer can submit bios with an
encryption context, such as filesystems, device-mapper targets, etc.

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

1 files changed, 166 insertions, 0 deletions

diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
new file mode 100644
index 000000000000..796f757fe8e9
--- /dev/null
+++ b/block/blk-crypto-internal.h
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef __LINUX_BLK_CRYPTO_INTERNAL_H
+#define __LINUX_BLK_CRYPTO_INTERNAL_H
+
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+
+/* Represents a crypto mode supported by blk-crypto  */
+struct blk_crypto_mode {
+	unsigned int keysize; /* key size in bytes */
+	unsigned int ivsize; /* iv size in bytes */
+};
+
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
+			     unsigned int inc);
+
+bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio);
+
+bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
+			     struct bio_crypt_ctx *bc2);
+
+static inline bool bio_crypt_ctx_back_mergeable(struct request *req,
+						struct bio *bio)
+{
+	return bio_crypt_ctx_mergeable(req->crypt_ctx, blk_rq_bytes(req),
+				       bio->bi_crypt_context);
+}
+
+static inline bool bio_crypt_ctx_front_mergeable(struct request *req,
+						 struct bio *bio)
+{
+	return bio_crypt_ctx_mergeable(bio->bi_crypt_context,
+				       bio->bi_iter.bi_size, req->crypt_ctx);
+}
+
+static inline bool bio_crypt_ctx_merge_rq(struct request *req,
+					  struct request *next)
+{
+	return bio_crypt_ctx_mergeable(req->crypt_ctx, blk_rq_bytes(req),
+				       next->crypt_ctx);
+}
+
+static inline void blk_crypto_rq_set_defaults(struct request *rq)
+{
+	rq->crypt_ctx = NULL;
+	rq->crypt_keyslot = NULL;
+}
+
+static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
+{
+	return rq->crypt_ctx;
+}
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline bool bio_crypt_rq_ctx_compatible(struct request *rq,
+					       struct bio *bio)
+{
+	return true;
+}
+
+static inline bool bio_crypt_ctx_front_mergeable(struct request *req,
+						 struct bio *bio)
+{
+	return true;
+}
+
+static inline bool bio_crypt_ctx_back_mergeable(struct request *req,
+						struct bio *bio)
+{
+	return true;
+}
+
+static inline bool bio_crypt_ctx_merge_rq(struct request *req,
+					  struct request *next)
+{
+	return true;
+}
+
+static inline void blk_crypto_rq_set_defaults(struct request *rq) { }
+
+static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
+{
+	return false;
+}
+
+#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
+static inline void bio_crypt_advance(struct bio *bio, unsigned int bytes)
+{
+	if (bio_has_crypt_ctx(bio))
+		__bio_crypt_advance(bio, bytes);
+}
+
+void __bio_crypt_free_ctx(struct bio *bio);
+static inline void bio_crypt_free_ctx(struct bio *bio)
+{
+	if (bio_has_crypt_ctx(bio))
+		__bio_crypt_free_ctx(bio);
+}
+
+static inline void bio_crypt_do_front_merge(struct request *rq,
+					    struct bio *bio)
+{
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+	if (bio_has_crypt_ctx(bio))
+		memcpy(rq->crypt_ctx->bc_dun, bio->bi_crypt_context->bc_dun,
+		       sizeof(rq->crypt_ctx->bc_dun));
+#endif
+}
+
+bool __blk_crypto_bio_prep(struct bio **bio_ptr);
+static inline bool blk_crypto_bio_prep(struct bio **bio_ptr)
+{
+	if (bio_has_crypt_ctx(*bio_ptr))
+		return __blk_crypto_bio_prep(bio_ptr);
+	return true;
+}
+
+blk_status_t __blk_crypto_init_request(struct request *rq);
+static inline blk_status_t blk_crypto_init_request(struct request *rq)
+{
+	if (blk_crypto_rq_is_encrypted(rq))
+		return __blk_crypto_init_request(rq);
+	return BLK_STS_OK;
+}
+
+void __blk_crypto_free_request(struct request *rq);
+static inline void blk_crypto_free_request(struct request *rq)
+{
+	if (blk_crypto_rq_is_encrypted(rq))
+		__blk_crypto_free_request(rq);
+}
+
+void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
+			      gfp_t gfp_mask);
+static inline void blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
+					  gfp_t gfp_mask)
+{
+	if (bio_has_crypt_ctx(bio))
+		__blk_crypto_rq_bio_prep(rq, bio, gfp_mask);
+}
+
+/**
+ * blk_crypto_insert_cloned_request - Prepare a cloned request to be inserted
+ *				      into a request queue.
+ * @rq: the request being queued
+ *
+ * Return: BLK_STS_OK on success, nonzero on error.
+ */
+static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq)
+{
+
+	if (blk_crypto_rq_is_encrypted(rq))
+		return blk_crypto_init_request(rq);
+	return BLK_STS_OK;
+}
+
+#endif /* __LINUX_BLK_CRYPTO_INTERNAL_H */