Re: [Qemu-devel] [PATCH 2/5] block: Remove dirty bitmaps from bdrv_move_feature_fields()

[Eric Blake <eblake@redhat.com>]

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On 03/14/2016 09:44 AM, Kevin Wolf wrote:
> This patch changes dirty bitmaps from following a BlockBackend in graph
> changes to sticking with the node they were created at. For the full
> discussion, read the following mailing list thread:
> 
>   [Qemu-block] block: Dirty bitmaps and COR in bdrv_move_feature_fields()
>   https://lists.nongnu.org/archive/html/qemu-block/2016-02/msg00745.html
> 
> In summary, the justification for this change is:
[snip nice list]
> 
> At the end of the day it seems to be very clear that it was a mistake to
> include dirty bitmaps in bdrv_move_feature_fields(). The functionality
> of moving bitmaps and/or attaching them to a BlockBackend instead will
> probably be needed, but it should be done with a new explicit QMP
> command or option.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 3 ---
>  1 file changed, 3 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

[Always interesting when a patch is way shorter than the justification
for why we need the patch]

> 
> diff --git a/block.c b/block.c
> index a75c4b3..698e2c7 100644
> --- a/block.c
> +++ b/block.c
> @@ -2284,9 +2284,6 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
>  
>      /* dev info */
>      bs_dest->enable_write_cache = bs_src->enable_write_cache;
> -
> -    /* dirty bitmap */
> -    bs_dest->dirty_bitmaps      = bs_src->dirty_bitmaps;
>  }
>  
>  static void change_parent_backing_link(BlockDriverState *from,
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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