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Re: [Qemu-devel] [PATCH 7/8] block/backup: support bitmap sync modes for


From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH 7/8] block/backup: support bitmap sync modes for non-bitmap backups
Date: Wed, 10 Jul 2019 18:48:47 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0

On 10.07.19 03:05, John Snow wrote:
> Accept bitmaps and sync policies for the other backup modes.
> This allows us to do things like create a bitmap synced to a full backup
> without a transaction, or start a resumable backup process.
> 
> Some combinations don't make sense, though:
> 
> - NEVER policy combined with any non-BITMAP mode doesn't do anything,
>   because the bitmap isn't used for input or output.
>   It's harmless, but is almost certainly never what the user wanted.
> 
> - sync=NONE is more questionable. It can't use on-success because this
>   job never completes with success anyway, and the resulting artifact
>   of 'always' is suspect: because we start with a full bitmap and only
>   copy out segments that get written to, the final output bitmap will
>   always be ... a fully set bitmap.
> 
>   Maybe there's contexts in which bitmaps make sense for sync=none,
>   but not without more severe changes to the current job, and omitting
>   it here doesn't prevent us from adding it later.
> 
> Signed-off-by: John Snow <address@hidden>
> ---
>  block/backup.c       |  8 +-------
>  blockdev.c           | 22 ++++++++++++++++++++++
>  qapi/block-core.json |  6 ++++--
>  3 files changed, 27 insertions(+), 9 deletions(-)

[...]

> diff --git a/blockdev.c b/blockdev.c
> index f0b7da53b0..bc152f8e0d 100644
> --- a/blockdev.c
> +++ b/blockdev.c

[...]

> +    if (!backup->has_bitmap && backup->has_bitmap_mode) {
> +        error_setg(errp, "Cannot specify Bitmap sync mode without a bitmap");

Any reason for capitalizing the first “Bitmap”?

With a reason or it fixed:

Reviewed-by: Max Reitz <address@hidden>

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