Re: [Qemu-devel] [PATCH v6 2/2] qemu-img: Document --force-share / -U

[Eric Blake <eblake@redhat.com>]

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On 01/30/2018 12:34 AM, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  qemu-img.texi | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 60a0e080c6..ec7e2f5d1e 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -86,6 +86,13 @@ 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)
> +If specified, @code{qemu-img} will open the image in shared mode, allowing
> +concurrent writers. For example, this can be used to get the image information

Actually, we only permit one writer at a time.  Would it be better to
say "allowing a concurrent writer"?

> +(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.

After all, we are stating that this process (which must be read-only,
because we can't have two writers at once) is permitting some other
process to be the concurrent writer (but not multiple processes to be
concurrent writers)


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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