Re: [PATCH for-5.1 v2 1/2] block/block-copy: always align copied region to cluster size

[Max Reitz]

On 10.08.20 11:55, Stefan Reiter wrote:
> Since commit 42ac214406e0 (block/block-copy: refactor task creation)
> block_copy_task_create calculates the area to be copied via
> bdrv_dirty_bitmap_next_dirty_area, but that can return an unaligned byte
> count if the image's last cluster end is not aligned to the bitmap's
> granularity.
> 
> Always ALIGN_UP the resulting bytes value to satisfy block_copy_do_copy,
> which requires the 'bytes' parameter to be aligned to cluster size.
> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
> ---
> 
> I've now marked it for-5.1 since it is just a fix, but it's probably okay if
> done later as well.

42ac214406e0 wasn’t in 5.0, so this would be a regression if we don’t
get it in 5.1.  I suppose this is an edge case, because most images
should be aligned to the cluster size, but I think objectively this is
something for 5.1.

So I’ll apply this series to my block branch:

https://git.xanclic.moe/XanClic/qemu/commits/branch/block

And I think I’m going to send a pull request tomorrow morning.  I see
there’s another patch for 5.1 on the list, so it should be OK.

If you want me to act on any of the suggestions I gave on your test,
feel free to say so and I’ll handle those that make sense to you (like,
I hope the s/4097/4096/ thing perhaps).

Thanks for finding and fixing this!

Max

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