Re: [Qemu-devel] [PATCH v5 2/2] qemu-img: Document --force-share / -U

[Max Reitz <mreitz@redhat.com>]

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On 2017-12-26 03:52, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  qemu-img.texi | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 60a0e080c6..e83e140f7a 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -86,6 +86,15 @@ exclusive with the @var{-O} parameters. It is currently required to also use
>  the @var{-n} parameter to skip image creation. This restriction may be relaxed
>  in a future release.
>  
> +@item --force-share (-U)
> +

So the previous patch makes the use of blank lines consistent and this
one breaks it again? :-)

> +If specified, @code{qemu-img} will open the image with shared permissions,
> +which makes it less likely to conflict with a running guest's permissions due
> +to image locking. For example, this can be used to get the image information
> +(with 'info' subcommand) when the image is used by a running guest. Note that
> +this could produce inconsistent results because of concurrent metadata changes,
> +etc. This option is only allowed when opening images in read-only mode.

I personally don't quite like the "makes it less likely to conflict",
because that makes it sound like qemu would be stupid and need a nudge
in the right direction -- when it's actually the user who does something
a bit risky (and qemu is right in forbidding it by default).  But since
it's only a read-only thing, I won't actually object to it.

(Maybe it should document more exactly what's happening, i.e. that this
option will allow concurrent writers (as a standard user, I wouldn't
know what "shared permissions" is supposed to mean).)

Max

> +
>  @item --backing-chain
>  will enumerate information about backing files in a disk image chain. Refer
>  below for further description.
> 



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