Re: [Qemu-devel] [PATCH v2 2/3] qcow2: rework the cluster compression routine

[Max Reitz]

On 04.07.19 15:09, Denis Plotnikov wrote:
> The patch allow to process image compression type defined
> in the image header and choose an appropriate method for
> image clusters (de)compression.
> 
> Signed-off-by: Denis Plotnikov <address@hidden>
> ---
>  block/qcow2.c | 93 ++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 73 insertions(+), 20 deletions(-)

I tried my best to rebase this patch on top of the current master, I
hope I did it right.

(A couple of the hunks in this patch are already in master.)

> diff --git a/block/qcow2.c b/block/qcow2.c
> index 8fa932a349..a107f76e98 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c

[...]

> @@ -4059,8 +4062,8 @@ static ssize_t qcow2_compress(void *dest, size_t 
> dest_size,
>   * Returns: 0 on success
>   *          -1 on fail

This should be fixed to reflect the new return values.

>   */
> -static ssize_t qcow2_decompress(void *dest, size_t dest_size,
> -                                const void *src, size_t src_size)
> +static ssize_t qcow2_zlib_decompress(void *dest, size_t dest_size,
> +                                     const void *src, size_t src_size)
>  {
>      int ret = 0;
>      z_stream strm;

[...]

> @@ -4153,20 +4156,67 @@ qcow2_co_do_compress(BlockDriverState *bs, void 
> *dest, size_t dest_size,
>      return arg.ret;
>  }
>  
> +/*
> + * qcow2_co_compress()
> + *
> + * Compress @src_size bytes of data using the compression
> + * method defined by the image compression type
> + *
> + * @dest - destination buffer, @dest_size bytes
> + * @src - source buffer, @src_size bytes
> + *
> + * Returns: 0 on success
> + *          a negative error code on fail
> + */
>  static ssize_t coroutine_fn
>  qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size,
>                    const void *src, size_t src_size)
>  {
> -    return qcow2_co_do_compress(bs, dest, dest_size, src, src_size,
> -                                qcow2_compress);
> +    BDRVQcow2State *s = bs->opaque;
> +    Qcow2CompressFunc fn;
> +
> +    switch (s->compression_type) {
> +    case QCOW2_COMPRESSION_TYPE_ZLIB:
> +        fn = qcow2_zlib_compress;
> +        break;
> +
> +    default:
> +        return -ENOTSUP;

A plain abort() would work, too.  (Your choice.)

> +    }
> +
> +    return qcow2_co_do_compress(bs, dest, dest_size, src, src_size, fn);
>  }
>  
> +/*
> + * qcow2_co_decompress()
> + *
> + * Decompress some data (not more than @src_size bytes) to produce exactly
> + * @dest_size bytes using the compression method defined by the image
> + * compression type
> + *
> + * @dest - destination buffer, @dest_size bytes
> + * @src - source buffer, @src_size bytes
> + *
> + * Returns: 0 on success
> + *          a negative error code on fail
> + */
>  static ssize_t coroutine_fn
>  qcow2_co_decompress(BlockDriverState *bs, void *dest, size_t dest_size,
>                      const void *src, size_t src_size)
>  {
> -    return qcow2_co_do_compress(bs, dest, dest_size, src, src_size,
> -                                qcow2_decompress);
> +    BDRVQcow2State *s = bs->opaque;
> +    Qcow2CompressFunc fn;
> +
> +    switch (s->compression_type) {
> +    case QCOW2_COMPRESSION_TYPE_ZLIB:
> +        fn = qcow2_zlib_decompress;
> +        break;
> +
> +    default:
> +        return -ENOTSUP;

Same here.

Max

> +    }
> +
> +    return qcow2_co_do_compress(bs, dest, dest_size, src, src_size, fn);
>  }

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