[PATCH v3 02/10] block: blk-crypto: introduce blk_crypto_bio_sectors_alignment()

[Satya Tangirala <satyat@google.com>]

The size of any bio must be aligned to the data unit size of the bio crypt
context (if it exists) of that bio. This must also be ensured whenever a
bio is split. Introduce blk_crypto_bio_sectors_alignment() that returns the
required alignment in sectors. The number of sectors passed to any call of
bio_split() must be aligned to blk_crypto_bio_sectors_alignment().

Signed-off-by: Satya Tangirala <satyat@google.com>
---
 block/blk-crypto-internal.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index 0d36aae538d7..7f1535cc7e7c 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -60,6 +60,21 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
 	return rq->crypt_ctx;
 }
 
+/*
+ * Returns the alignment requirement for the number of sectors in this bio based
+ * on its bi_crypt_context. Any bios split from this bio must follow this
+ * alignment requirement as well. Note that a bio must contain a whole number of
+ * crypto data units (which is selected by the submitter of bio), since
+ * encryption/decryption can only be performed on a complete crypto data unit.
+ */
+static inline unsigned int blk_crypto_bio_sectors_alignment(struct bio *bio)
+{
+	if (!bio_has_crypt_ctx(bio))
+		return 1;
+	return bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size >>
+								SECTOR_SHIFT;
+}
+
 #else /* CONFIG_BLK_INLINE_ENCRYPTION */
 
 static inline bool bio_crypt_rq_ctx_compatible(struct request *rq,
@@ -93,6 +108,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
 	return false;
 }
 
+static inline unsigned int blk_crypto_bio_sectors_alignment(struct bio *bio)
+{
+	return 1;
+}
+
 #endif /* CONFIG_BLK_INLINE_ENCRYPTION */
 
 void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
-- 
2.32.0.rc1.229.g3e70b5a671-goog