[PATCH 26/32] qemu: Rewrite bitmap handling for block commit

[Eric Blake]

On 6/15/20 12:10 PM, Peter Krempa wrote:
> Reuse qemuBlockGetBitmapMergeActions which allows to remove the ad-hoc

s/allows to remove/allows the removal of/

> implementatio of bitmap merging for block commit. The new approach is

implementation

> way simpler and more robust and also allows us to get rid of the
> disabling of bitmaps done prior to the start as we actually do want to
> update the bitmaps in the base.

What if the commit fails, but we have merged in portions of the bitmap? 
In practice, this merely means that a future attempt to use that bitmap 
in the backing file will now copy more data than previously necessary; 
what's more, if we try a commit again (if the failure was transient), 
we'll be setting those same bits again.  So yeah, I don't think it hurts 
to not disable the bitmaps in the backing files.

> 
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>   src/qemu/qemu_block.c                         | 203 +-----------------
>   src/qemu/qemu_block.h                         |  11 +-
>   src/qemu/qemu_blockjob.c                      |  25 ++-
>   src/qemu/qemu_driver.c                        |  56 +----
>   tests/qemublocktest.c                         |  18 +-
>   .../qemublocktestdata/bitmapblockcommit/empty |   1 -
>   6 files changed, 42 insertions(+), 272 deletions(-)
> 

> @@ -3332,95 +3222,20 @@ qemuBlockBitmapsHandleCommitFinishIterate(void *payload,
>   int
>   qemuBlockBitmapsHandleCommitFinish(virStorageSourcePtr topsrc,
>                                      virStorageSourcePtr basesrc,
> +                                   bool active,
>                                      virHashTablePtr blockNamedNodeData,
> -                                   virJSONValuePtr *actions,
> -                                   char **disabledBitmapsBase)
> +                                   virJSONValuePtr *actions)
>   {

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

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org