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

[Max Reitz]

On 02.04.20 11:36, 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.)

So as far as I can tell we still don’t ensure that the image is aligned
to 1 MB blocks?

Well, as long as it’s at least possible for the user to create valid
images, that’s better.

> Fixes: https://bugs.launchpad.net/bugs/1870098
> Reported-by: Tobias Witek
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  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);

And the old code just looks like a wrong DIV_ROUND_UP() attempt.  So:

Reviewed-by: Max Reitz <address@hidden>

>  
>      ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0);
>      if (ret < 0) {
>

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