Backing files and raw external data files are mutually exclusive.
The documentation of the raw external data bit (in autoclear_features)
already indicates that, but we should also mention it on the other
side.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 docs/interop/qcow2.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
index 640e0eca40..298a031310 100644
--- a/docs/interop/qcow2.txt
+++ b/docs/interop/qcow2.txt
@@ -25,6 +25,9 @@ The first cluster of a qcow2 image contains the file header:
                     is stored (NB: The string is not null terminated). 0 if the
                     image doesn't have a backing file.
 
+                    Note: backing files are incompatible with raw external data
+                    files (auto-clear feature bit 1).
+
          16 - 19:   backing_file_size
                     Length of the backing file name in bytes. Must not be
                     longer than 1023 bytes. Undefined if the image doesn't have
-- 
2.20.1

Am 10.04.2020 um 14:18 hat Alberto Garcia geschrieben:
> Backing files and raw external data files are mutually exclusive.
> The documentation of the raw external data bit (in autoclear_features)
> already indicates that, but we should also mention it on the other
> side.
> 
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Alberto Garcia <berto@igalia.com>

Thanks, applied to the block branch.

I don't think this is critical for 5.0, so if I make a pull request for
other reasons, I'll include it, but if you agree, I won't send one just
for this patch.

Kevin

On Tue 14 Apr 2020 05:31:26 PM CEST, Kevin Wolf <kwolf@redhat.com> wrote:

> I don't think this is critical for 5.0, so if I make a pull request
> for other reasons, I'll include it, but if you agree, I won't send one
> just for this patch.

Sure, no problem.

Berto

On 4/10/20 7:18 AM, Alberto Garcia wrote:
> Backing files and raw external data files are mutually exclusive.
> The documentation of the raw external data bit (in autoclear_features)
> already indicates that, but we should also mention it on the other
> side.
> 
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>   docs/interop/qcow2.txt | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
> index 640e0eca40..298a031310 100644
> --- a/docs/interop/qcow2.txt
> +++ b/docs/interop/qcow2.txt
> @@ -25,6 +25,9 @@ The first cluster of a qcow2 image contains the file header:
>                       is stored (NB: The string is not null terminated). 0 if the
>                       image doesn't have a backing file.
>   
> +                    Note: backing files are incompatible with raw external data
> +                    files (auto-clear feature bit 1).
> +
>            16 - 19:   backing_file_size
>                       Length of the backing file name in bytes. Must not be
>                       longer than 1023 bytes. Undefined if the image doesn't have
> 

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

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