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

[Fam Zheng <famz@redhat.com>]

On Wed, 05/13 16:27, Alberto Garcia wrote:
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>

Reviewed-by: Fam Zheng <famz@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
>  ===============
> -- 
> 2.1.4
> 
>