Re: [Qemu-block] [PATCH 03/20] qcow2: Extend spec for external data files

[Stefan Hajnoczi]

On Wed, Feb 27, 2019 at 06:22:39PM +0100, Kevin Wolf wrote:
> -                    Bits 2-63:  Reserved (set to 0)
> +                    Bit 2:      External data file bit.  If this bit is set, 
> an
> +                                external data file is used. Guest clusters 
> are
> +                                then stored in the external data file. For 
> such
> +                                images, clusters in the external data file 
> are
> +                                not refcounted. The offset field in the
> +                                Standard Cluster Descriptor must match the
> +                                guest offset and neither compressed clusters
> +                                nor internal snapshots are supported.
> +
> +                                An external data file name header extension 
> may
> +                                be present if this bit is set.

This sentence is clearer if the header extension name is made prominent:

  An "external data file name" header extension

Or

  An External Data File Name header extension

(In the previous paragraph Standard Cluster Descriptor is also
capitalized.)

> @@ -148,6 +170,7 @@ be stored. Each extension has a structure like the 
> following:
>                          0x6803f857 - Feature name table
>                          0x23852875 - Bitmaps extension
>                          0x0537be77 - Full disk encryption header pointer
> +                        0x44415441 - External data file name

This new header extension isn't described in this patch?

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