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

[Mikulas Patocka <mpatocka@redhat.com>]

Hi

What about using the REQ_META flag (it is set on metadata bios and cleared 
on data bios), instead of adding a new flag with the same meaning?

Mikulas


On Fri, 18 Oct 2024, Eric Biggers wrote:

> From: Eric Biggers <ebiggers@google.com>
> 
> 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@google.com>
> ---
>  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
>