[RFC PATCH 2/4] block: add the bi_skip_dm_default_key flag

[Eric Biggers <ebiggers@xxxxxxxxxx>]

From: Eric Biggers <ebiggers@xxxxxxxxxx>

Add a flag bi_skip_dm_default_key to struct bio.  This flag indicates
that dm-default-key should not en/decrypt the bio, due to it targeting
the contents of an encrypted file.

When a bio is cloned, copy the bi_skip_dm_default_key flag.

Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 block/bio.c                 |  3 +++
 block/blk-crypto-fallback.c |  2 ++
 include/linux/blk-crypto.h  | 36 ++++++++++++++++++++++++++++++++++++
 include/linux/blk_types.h   |  3 +++
 4 files changed, 44 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index ac4d77c889322..5ff0b66e47a42 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -267,10 +267,13 @@ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
 	bio->bi_iocost_cost = 0;
 #endif
 #endif
 #ifdef CONFIG_BLK_INLINE_ENCRYPTION
 	bio->bi_crypt_context = NULL;
+#if IS_ENABLED(CONFIG_DM_DEFAULT_KEY)
+	bio->bi_skip_dm_default_key = false;
+#endif
 #endif
 #ifdef CONFIG_BLK_DEV_INTEGRITY
 	bio->bi_integrity = NULL;
 #endif
 	bio->bi_vcnt = 0;
diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
index b1e7415f8439c..dd5f1edcc44b3 100644
--- a/block/blk-crypto-fallback.c
+++ b/block/blk-crypto-fallback.c
@@ -179,10 +179,12 @@ static struct bio *blk_crypto_fallback_clone_bio(struct bio *bio_src)
 	bio_for_each_segment(bv, bio_src, iter)
 		bio->bi_io_vec[bio->bi_vcnt++] = bv;
 
 	bio_clone_blkg_association(bio, bio_src);
 
+	bio_clone_skip_dm_default_key(bio, bio_src);
+
 	return bio;
 }
 
 static bool
 blk_crypto_fallback_alloc_cipher_req(struct blk_crypto_keyslot *slot,
diff --git a/include/linux/blk-crypto.h b/include/linux/blk-crypto.h
index 5e5822c18ee41..f1f3d546c53e5 100644
--- a/include/linux/blk-crypto.h
+++ b/include/linux/blk-crypto.h
@@ -110,10 +110,13 @@ static inline bool bio_has_crypt_ctx(struct bio *bio)
 	return false;
 }
 
 #endif /* CONFIG_BLK_INLINE_ENCRYPTION */
 
+static inline void bio_clone_skip_dm_default_key(struct bio *dst,
+						 const struct bio *src);
+
 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask);
 /**
  * bio_crypt_clone - clone bio encryption context
  * @dst: destination bio
  * @src: source bio
@@ -125,11 +128,44 @@ int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask);
  *	   @gfp_mask doesn't include %__GFP_DIRECT_RECLAIM.
  */
 static inline int bio_crypt_clone(struct bio *dst, struct bio *src,
 				  gfp_t gfp_mask)
 {
+	bio_clone_skip_dm_default_key(dst, src);
 	if (bio_has_crypt_ctx(src))
 		return __bio_crypt_clone(dst, src, gfp_mask);
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_DM_DEFAULT_KEY)
+static inline void bio_set_skip_dm_default_key(struct bio *bio)
+{
+	bio->bi_skip_dm_default_key = true;
+}
+
+static inline bool bio_should_skip_dm_default_key(const struct bio *bio)
+{
+	return bio->bi_skip_dm_default_key;
+}
+
+static inline void bio_clone_skip_dm_default_key(struct bio *dst,
+						 const struct bio *src)
+{
+	dst->bi_skip_dm_default_key = src->bi_skip_dm_default_key;
+}
+#else /* CONFIG_DM_DEFAULT_KEY */
+static inline void bio_set_skip_dm_default_key(struct bio *bio)
+{
+}
+
+static inline bool bio_should_skip_dm_default_key(const struct bio *bio)
+{
+	return false;
+}
+
+static inline void bio_clone_skip_dm_default_key(struct bio *dst,
+						 const struct bio *src)
+{
+}
+#endif /* !CONFIG_DM_DEFAULT_KEY */
+
 #endif /* __LINUX_BLK_CRYPTO_H */
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dce7615c35e7e..2ee6a7e570796 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -247,10 +247,13 @@ struct bio {
 #endif
 #endif
 
 #ifdef CONFIG_BLK_INLINE_ENCRYPTION
 	struct bio_crypt_ctx	*bi_crypt_context;
+#if IS_ENABLED(CONFIG_DM_DEFAULT_KEY)
+	bool			bi_skip_dm_default_key;
+#endif
 #endif
 
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
 	struct bio_integrity_payload *bi_integrity; /* data integrity */
 #endif
-- 
2.47.0