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

[Vladimir Sementsov-Ogievskiy]

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>
> ---
>   block/qcow2-cluster.c | 35 +++++--------------
>   block/qcow2-threads.c | 81 ++++++++++++++++++++++++++++++++++++-------
>   block/qcow2.c         |  5 +--
>   block/qcow2.h         |  8 ++---
>   4 files changed, 83 insertions(+), 46 deletions(-)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index bfeb0241d7..f42b8a404c 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -462,28 +462,6 @@ static int coroutine_fn 
> do_perform_cow_read(BlockDriverState *bs,
>       return 0;
>   }
>   
> -static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
> -                                                uint64_t src_cluster_offset,
> -                                                uint64_t cluster_offset,
> -                                                unsigned offset_in_cluster,
> -                                                uint8_t *buffer,
> -                                                unsigned bytes)
> -{
> -    if (bytes && bs->encrypted) {
> -        BDRVQcow2State *s = bs->opaque;
> -        assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
> -        assert((bytes & ~BDRV_SECTOR_MASK) == 0);
> -        assert(s->crypto);
> -        if (qcow2_co_encrypt(bs,
> -                start_of_cluster(s, cluster_offset + offset_in_cluster),
> -                src_cluster_offset + offset_in_cluster,
> -                buffer, bytes) < 0) {
> -            return false;
> -        }
> -    }
> -    return true;
> -}
> -
>   static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
>                                                uint64_t cluster_offset,
>                                                unsigned offset_in_cluster,
> @@ -891,11 +869,14 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta 
> *m)
>   
>       /* Encrypt the data if necessary before writing it */
>       if (bs->encrypted) {
> -        if (!do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
> -                                    start->offset, start_buffer,
> -                                    start->nb_bytes) ||
> -            !do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
> -                                    end->offset, end_buffer, end->nb_bytes)) 
> {
> +        if (!qcow2_co_encrypt(bs,
> +                              m->offset + start->offset,
> +                              m->alloc_offset + start->offset,
> +                              start_buffer, start->nb_bytes) ||

You got caught)
second argument qcow2_co_encrypt is host_offset and third is guest_offset.

I noticed this difference when reviewing previous version, and it's actually
additional reason to drop the function. Unfortunately, I didn't said.

Also, we can use return value of qcow2_co_encrypt instead of dropping it,

something like classical

ret = qcow2_co_encrypt(..)
if (ret < 0) {
    goto fail;
}

ret = qcow2_co_encrypt(..)
if (ret < 0) {
    goto fail;
}

Also, IMHO, too much changes too keep reviewed-by mark. Still, maybe it's my
"with it least fixed" is misleading, may be interpreted like removing the
function and corresponding refactoring is included..


> +            !qcow2_co_encrypt(bs,
> +                              m->offset + end->offset,
> +                              m->alloc_offset + end->offset,
> +                              end_buffer, end->nb_bytes)) {
>               ret = -EIO;
>               goto fail;
>           }
> 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;
> +
>       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);
>   }
>   
> +
> +/*
> + * 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);
> +
> +    BDRVQcow2State *s = bs->opaque;
> +    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);

Hmm, better to move these asertions to _encdec I think, and don't duplicate
them in two functions.

> +
> +    if (!len) {
> +        return 0;
> +    }

Aha, that's why you don't check this in perform_cow. That's OK,
but still, better keep it in _encdec and don't duplicate.

> +
> +    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
> +                           qcrypto_block_encrypt);
>   }
>   
> +
> +/*
> + * qcow2_co_decrypt()
> + *
> + * Decrypts one or more contiguous aligned sectors
> + * Similar to qcow2_co_encrypt
> + */
> +
>   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);
> +    BDRVQcow2State *s = bs->opaque;
> +    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_decrypt);
>   }
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 57734f20cf..ac768092bb 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2069,7 +2069,8 @@ static coroutine_fn int 
> qcow2_co_preadv_part(BlockDriverState *bs,
>   
>                   assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
>                   assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> -                if (qcow2_co_decrypt(bs, cluster_offset, offset,
> +                if (qcow2_co_decrypt(bs, cluster_offset + offset_in_cluster,
> +                                     offset,
>                                        cluster_data, cur_bytes) < 0) {
>                       ret = -EIO;
>                       goto fail;
> @@ -2288,7 +2289,7 @@ static coroutine_fn int qcow2_co_pwritev_part(
>               qemu_iovec_to_buf(qiov, qiov_offset + bytes_done,
>                                 cluster_data, cur_bytes);
>   
> -            if (qcow2_co_encrypt(bs, cluster_offset, offset,
> +            if (qcow2_co_encrypt(bs, cluster_offset + offset_in_cluster, 
> offset,
>                                    cluster_data, cur_bytes) < 0) {
>                   ret = -EIO;
>                   goto out_unlocked;
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 998bcdaef1..a488d761ff 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -758,10 +758,10 @@ ssize_t coroutine_fn
>   qcow2_co_decompress(BlockDriverState *bs, void *dest, size_t dest_size,
>                       const void *src, size_t src_size);
>   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);
>   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);
>   
>   #endif
> 


-- 
Best regards,
Vladimir