Re: [Qemu-devel] [PATCH v2 09/13] RFC: crypto: Rely on block layer for fragmentation

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Nov 14, 2018 at 08:03:30PM -0600, Eric Blake wrote:
> No need to reimplement fragmentation to BLOCK_CRYPTO_MAX_IO_SIZE
> ourselves when we can ask the block layer to do it for us.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> ---
> Question - is this patch for 'crypto' acceptable, or should we stick
> with just the previous one that marks things as 64-bit clean?

Unless I'm missing something, this is functionally equivalent to
the existing code, and is simpler to read, so I don't see any
obvious downside  to this patch.

Assuming that you've run 'qemu-iotests/check -luks' on it to
validate it then ...

   Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>



> ---
>  block/crypto.c | 80 +++++++++++++++++++-------------------------------
>  1 file changed, 30 insertions(+), 50 deletions(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index 259ef2649e1..b004cef22c2 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -328,8 +328,6 @@ block_crypto_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>                         QEMUIOVector *qiov, int flags)
>  {
>      BlockCrypto *crypto = bs->opaque;
> -    uint64_t cur_bytes; /* number of bytes in current iteration */
> -    uint64_t bytes_done = 0;
>      uint8_t *cipher_data = NULL;
>      QEMUIOVector hd_qiov;
>      int ret = 0;
> @@ -346,38 +344,30 @@ block_crypto_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      /* Bounce buffer because we don't wish to expose cipher text
>       * in qiov which points to guest memory.
>       */
> -    cipher_data =
> -        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
> -                                              qiov->size));
> +    assert(qiov->size <= BLOCK_CRYPTO_MAX_IO_SIZE);
> +    cipher_data = qemu_try_blockalign(bs->file->bs, qiov->size);
>      if (cipher_data == NULL) {
>          ret = -ENOMEM;
>          goto cleanup;
>      }
> 
> -    while (bytes) {
> -        cur_bytes = MIN(bytes, BLOCK_CRYPTO_MAX_IO_SIZE);
> +    qemu_iovec_reset(&hd_qiov);
> +    qemu_iovec_add(&hd_qiov, cipher_data, bytes);
> 
> -        qemu_iovec_reset(&hd_qiov);
> -        qemu_iovec_add(&hd_qiov, cipher_data, cur_bytes);
> -
> -        ret = bdrv_co_preadv(bs->file, payload_offset + offset + bytes_done,
> -                             cur_bytes, &hd_qiov, 0);
> -        if (ret < 0) {
> -            goto cleanup;
> -        }
> -
> -        if (qcrypto_block_decrypt(crypto->block, offset + bytes_done,
> -                                  cipher_data, cur_bytes, NULL) < 0) {
> -            ret = -EIO;
> -            goto cleanup;
> -        }
> -
> -        qemu_iovec_from_buf(qiov, bytes_done, cipher_data, cur_bytes);
> +    ret = bdrv_co_preadv(bs->file, payload_offset + offset, bytes,
> +                         &hd_qiov, 0);
> +    if (ret < 0) {
> +        goto cleanup;
> +    }
> 
> -        bytes -= cur_bytes;
> -        bytes_done += cur_bytes;
> +    if (qcrypto_block_decrypt(crypto->block, offset,
> +                              cipher_data, bytes, NULL) < 0) {
> +        ret = -EIO;
> +        goto cleanup;
>      }
> 
> +    qemu_iovec_from_buf(qiov, 0, cipher_data, bytes);
> +
>   cleanup:
>      qemu_iovec_destroy(&hd_qiov);
>      qemu_vfree(cipher_data);
> @@ -391,8 +381,6 @@ block_crypto_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>                          QEMUIOVector *qiov, int flags)
>  {
>      BlockCrypto *crypto = bs->opaque;
> -    uint64_t cur_bytes; /* number of bytes in current iteration */
> -    uint64_t bytes_done = 0;
>      uint8_t *cipher_data = NULL;
>      QEMUIOVector hd_qiov;
>      int ret = 0;
> @@ -409,36 +397,28 @@ block_crypto_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      /* Bounce buffer because we're not permitted to touch
>       * contents of qiov - it points to guest memory.
>       */
> -    cipher_data =
> -        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
> -                                              qiov->size));
> +    assert(qiov->size <= BLOCK_CRYPTO_MAX_IO_SIZE);
> +    cipher_data = qemu_try_blockalign(bs->file->bs, qiov->size);
>      if (cipher_data == NULL) {
>          ret = -ENOMEM;
>          goto cleanup;
>      }
> 
> -    while (bytes) {
> -        cur_bytes = MIN(bytes, BLOCK_CRYPTO_MAX_IO_SIZE);
> +    qemu_iovec_to_buf(qiov, 0, cipher_data, bytes);
> 
> -        qemu_iovec_to_buf(qiov, bytes_done, cipher_data, cur_bytes);
> +    if (qcrypto_block_encrypt(crypto->block, offset,
> +                              cipher_data, bytes, NULL) < 0) {
> +        ret = -EIO;
> +        goto cleanup;
> +    }
> 
> -        if (qcrypto_block_encrypt(crypto->block, offset + bytes_done,
> -                                  cipher_data, cur_bytes, NULL) < 0) {
> -            ret = -EIO;
> -            goto cleanup;
> -        }
> +    qemu_iovec_reset(&hd_qiov);
> +    qemu_iovec_add(&hd_qiov, cipher_data, bytes);
> 
> -        qemu_iovec_reset(&hd_qiov);
> -        qemu_iovec_add(&hd_qiov, cipher_data, cur_bytes);
> -
> -        ret = bdrv_co_pwritev(bs->file, payload_offset + offset + bytes_done,
> -                              cur_bytes, &hd_qiov, flags);
> -        if (ret < 0) {
> -            goto cleanup;
> -        }
> -
> -        bytes -= cur_bytes;
> -        bytes_done += cur_bytes;
> +    ret = bdrv_co_pwritev(bs->file, payload_offset + offset,
> +                          bytes, &hd_qiov, flags);
> +    if (ret < 0) {
> +        goto cleanup;
>      }
> 
>   cleanup:
> @@ -453,7 +433,7 @@ static void block_crypto_refresh_limits(BlockDriverState *bs, Error **errp)
>      BlockCrypto *crypto = bs->opaque;
>      uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
>      bs->bl.request_alignment = sector_size; /* No sub-sector I/O */
> -    bs->bl.max_transfer = INT64_MAX;
> +    bs->bl.max_transfer = BLOCK_CRYPTO_MAX_IO_SIZE;
>  }
> 
> 
> -- 
> 2.17.2
> 
> 

Regards,
Daniel
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