Re: [Qemu-devel] [PATCH 06/11] docs: Document how to stream to an intermediate layer

[Max Reitz <mreitz@redhat.com>]

On 24.04.2015 13:40, Alberto Garcia wrote:
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Reviewed-by: Max Reitz <mreitz@redhat.com>

Please remove my R-b if you change the patch in some non-insignificant 
way (like, obvious conflict resolution while rebasing is fine, 
differences in the patch context are almost always fine, too, and so on; 
but functional changes to code added or, in this case, semantic changes 
to text added to documentation are not).

But I'm fine with the new version, too, so after having said the 
necessary I'll just renew my R-b:

Reviewed-by: Max Reitz <mreitz@redhat.com>

> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>   docs/live-block-ops.txt | 31 ++++++++++++++++++++-----------
>   1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/docs/live-block-ops.txt b/docs/live-block-ops.txt
> index a257087..a05d869 100644
> --- a/docs/live-block-ops.txt
> +++ b/docs/live-block-ops.txt
> @@ -10,9 +10,9 @@ Snapshot live merge
>   Given a snapshot chain, described in this document in the following
>   format:
>   
> -[A] -> [B] -> [C] -> [D]
> +[A] <- [B] <- [C] <- [D] <- [E]
>   
> -Where the rightmost object ([D] in the example) described is the current
> +Where the rightmost object ([E] in the example) described is the current
>   image which the guest OS has write access to. To the left of it is its base
>   image, and so on accordingly until the leftmost image, which has no
>   base.
> @@ -21,11 +21,14 @@ The snapshot live merge operation transforms such a chain into a
>   smaller one with fewer elements, such as this transformation relative
>   to the first example:
>   
> -[A] -> [D]
> +[A] <- [E]
>   
> -Currently only forward merge with target being the active image is
> -supported, that is, data copy is performed in the right direction with
> -destination being the rightmost image.
> +Data is copied in the right direction with destination being the
> +rightmost image, but any other intermediate image can be specified
> +instead. In this example data is copied from [C] into [D], so [D] can
> +be backed by [B]:
> +
> +[A] <- [B] <- [D] <- [E]
>   
>   The operation is implemented in QEMU through image streaming facilities.
>   
> @@ -35,14 +38,20 @@ streaming operation completes it raises a QMP event. 'block_stream'
>   copies data from the backing file(s) into the active image. When finished,
>   it adjusts the backing file pointer.
>   
> -The 'base' parameter specifies an image which data need not be streamed from.
> -This image will be used as the backing file for the active image when the
> -operation is finished.
> +The 'base' parameter specifies an image which data need not be
> +streamed from. This image will be used as the backing file for the
> +destination image when the operation is finished.
> +
> +In the first example above, the command would be:
> +
> +(qemu) block_stream virtio0 file-A.img
>   
> -In the example above, the command would be:
> +In order to specify a destination image different from the active
> +(rightmost) one we can use its (previously set) node name instead.
>   
> -(qemu) block_stream virtio0 A
> +In the second example above, the command would be:
>   
> +(qemu) block_stream node-D file-B.img
>   
>   Live block copy
>   ===============