[dm-devel] [PATCH v4] crypto: xts - Drop use of auxiliary buffer

[Eric Biggers]

Hi Ondrej,

On Mon, Sep 10, 2018 at 01:28:41PM +0200, Ondrej Mosnacek wrote:
>  
> -static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
> +static int xor_tweak_pre(struct skcipher_request *req)
>  {
> -	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
> -	struct rctx *rctx = skcipher_request_ctx(req);
> -	struct skcipher_request *subreq;
> -	gfp_t gfp;
> -
> -	subreq = &rctx->subreq;
> -	skcipher_request_set_tfm(subreq, ctx->child);
> -	skcipher_request_set_callback(subreq, req->base.flags, done, req);
> -
> -	gfp = req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
> -							   GFP_ATOMIC;
> -	rctx->ext = NULL;
> -
> -	subreq->cryptlen = XTS_BUFFER_SIZE;
> -	if (req->cryptlen > XTS_BUFFER_SIZE) {
> -		unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);
> -
> -		rctx->ext = kmalloc(n, gfp);
> -		if (rctx->ext)
> -			subreq->cryptlen = n;
> -	}
> -
> -	rctx->src = req->src;
> -	rctx->dst = req->dst;
> -	rctx->left = req->cryptlen;
> -
> -	/* calculate first value of T */
> -	crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
> -
> -	return 0;
> +	return xor_tweak(req, false);
>  }
>  
> -static void exit_crypt(struct skcipher_request *req)
> +static int xor_tweak_post(struct skcipher_request *req)
>  {
> -	struct rctx *rctx = skcipher_request_ctx(req);
> -
> -	rctx->left = 0;
> -
> -	if (rctx->ext)
> -		kzfree(rctx->ext);
> +	return xor_tweak(req, false);
>  }

I think you meant 'xor_tweak(req, true);' here?

> +static void crypt_done(struct crypto_async_request *areq, int err)
>  {
>  	struct skcipher_request *req = areq->data;
> -	struct skcipher_request *subreq;
> -	struct rctx *rctx;
> -
> -	rctx = skcipher_request_ctx(req);
> -
> -	if (err == -EINPROGRESS) {
> -		if (rctx->left != req->cryptlen)
> -			return;
> -		goto out;
> -	}
> -
> -	subreq = &rctx->subreq;
> -	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
>  
> -	err = do_encrypt(req, err ?: post_crypt(req));
> -	if (rctx->left)
> -		return;
> +	if (!err)
> +		err = xor_tweak(req, true);

Use xor_tweak_post()?

Note that you could also change the bool to

enum {
	FIRST_PASS,
	SECOND_PASS,
}

if you find the bool to be unclear.

Thanks,

- Eric