Re: [PATCH for-5.0] vpc: Don't round up already aligned BAT sizes

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/2/20 11:36 AM, Kevin Wolf wrote:
> As reported on Launchpad, Azure apparently doesn't accept images for
> upload that are not both aligned to 1 MB blocks and have a BAT size that
> matches the image size exactly.
> 
> As far as I can tell, there is no real reason why we create a BAT that
> is one entry longer than necessary for aligned image sizes, so change
> that.
> 
> (Even though the condition is only mentioned as "should" in the spec and
> previous products accepted larger BATs - but we'll try to maintain
> compatibility with as many of Microsoft's ever-changing interpretations
> of the VHD spec as possible.)
> 
> Fixes: https://bugs.launchpad.net/bugs/1870098
> Reported-by: Tobias Witek
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/vpc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/vpc.c b/block/vpc.c
> index 6df75e22dc..d8141b52da 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -835,7 +835,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf,
>   
>       /* Write the footer (twice: at the beginning and at the end) */
>       block_size = 0x200000;
> -    num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
> +    num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512);
>   
>       ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0);
>       if (ret < 0) {
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>