Re: [Qemu-stable] [PATCH v6 2/3] block/qcow2: refactor threaded encryption code

[Vladimir Sementsov-Ogievskiy]

and a bit about empty lines

13.09.2019 20:27, Maxim Levitsky wrote:
> Change the qcow2_co_encrypt to just receive full host and
> guest offsets and in pariticular remove the
> offset_in_cluster parameter of do_perform_cow_encrypt,
> since it is misleading, because that offset can be larger than
> cluster size currently.
> 
> Remove the do_perform_cow_encrypt by merging it with
> qcow2_co_encrypt
> 
> Also document the qcow2_co_encrypt arguments to prevent
> that bug from happening again
> 
> Signed-off-by: Maxim Levitsky <address@hidden>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---

[..]

> diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
> index 3b1e63fe41..b31d45fb2b 100644
> --- a/block/qcow2-threads.c
> +++ b/block/qcow2-threads.c
> @@ -234,15 +234,15 @@ static int qcow2_encdec_pool_func(void *opaque)
>   }
>   
>   static int coroutine_fn
> -qcow2_co_encdec(BlockDriverState *bs, uint64_t file_cluster_offset,
> -                  uint64_t offset, void *buf, size_t len, Qcow2EncDecFunc 
> func)
> +qcow2_co_encdec(BlockDriverState *bs, uint64_t host_offset,
> +                uint64_t guest_offset, void *buf, size_t len,
> +                Qcow2EncDecFunc func)
>   {
>       BDRVQcow2State *s = bs->opaque;
> +

Don't see real benefit in separating one variable initialization from another 
one here,
but I don't mind, it's OK of course.

>       Qcow2EncDecData arg = {
>           .block = s->crypto,
> -        .offset = s->crypt_physical_offset ?
> -                      file_cluster_offset + offset_into_cluster(s, offset) :
> -                      offset,
> +        .offset = s->crypt_physical_offset ? host_offset : guest_offset,
>           .buf = buf,
>           .len = len,
>           .func = func,
> @@ -251,18 +251,73 @@ qcow2_co_encdec(BlockDriverState *bs, uint64_t 
> file_cluster_offset,
>       return qcow2_co_process(bs, qcow2_encdec_pool_func, &arg);
>   }
>   
> +

Hmm, in this file doubled empty lines
are used to separate "Compression" and "Cryptography"
sections. And all other splits are one-empty-line.

> +/*
> + * qcow2_co_encrypt()
> + *
> + * Encrypts one or more contiguous aligned sectors
> + *
> + * @host_offset - underlying storage offset of the first sector of the
> + * data to be encrypted
> + *
> + * @guest_offset - guest (virtual) offset of the first sector of the
> + * data to be encrypted
> + *
> + * @buf - buffer with the data to encrypt, that after encryption
> + *        will be written to the underlying storage device at
> + *        @host_offset
> + *
> + * @len - length of the buffer (must be a BDRV_SECTOR_SIZE multiple)
> + *
> + * Depending on the encryption method, @host_offset and/or @guest_offset
> + * may be used for generating the initialization vector for
> + * encryption.
> + *
> + * Note that while the whole range must be aligned on sectors, it
> + * does not have to be aligned on clusters and can also cross cluster
> + * boundaries
> + */
>   int coroutine_fn
> -qcow2_co_encrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
> -                 uint64_t offset, void *buf, size_t len)
> +qcow2_co_encrypt(BlockDriverState *bs, uint64_t host_offset,
> +                 uint64_t guest_offset, void *buf, size_t len)
>   {
> -    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
> -                             qcrypto_block_encrypt);
> +

This empty line is not needed for sure

> +    BDRVQcow2State *s = bs->opaque;

But it's common practice to split variables definition from code by empty line 
here

> +    assert(QEMU_IS_ALIGNED(guest_offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(host_offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(len, BDRV_SECTOR_SIZE));
> +    assert(s->crypto);
> +
> +    if (!len) {
> +        return 0;
> +    }
> +
> +    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
> +                           qcrypto_block_encrypt);
>   }
>   
> +

IMHO extra one (see above)

> +/*
> + * qcow2_co_decrypt()
> + *
> + * Decrypts one or more contiguous aligned sectors
> + * Similar to qcow2_co_encrypt
> + */
> +

Here you replaced one extra empty line by another

>   int coroutine_fn
> -qcow2_co_decrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
> -                 uint64_t offset, void *buf, size_t len)
> +qcow2_co_decrypt(BlockDriverState *bs, uint64_t host_offset,
> +                 uint64_t guest_offset, void *buf, size_t len)
>   {
> -    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
> -                             qcrypto_block_decrypt);



-- 
Best regards,
Vladimir