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

[Fam Zheng]

On Tue, Jan 30, 2018 at 12:01 AM, Max Reitz <address@hidden> wrote:
> On 2017-12-26 03:52, Fam Zheng wrote:
>> Signed-off-by: Fam Zheng <address@hidden>
>> Reviewed-by: Stefan Hajnoczi <address@hidden>
>> Reviewed-by: Kashyap Chamarthy <address@hidden>
>> Signed-off-by: Kevin Wolf <address@hidden>
>> ---
>>  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.
>>
>> address@hidden --force-share (-U)
>> +
>
> So the previous patch makes the use of blank lines consistent and this
> one breaks it again? :-)

Good point, will fix.

>
>> +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).)

Makes sense to me. Sending v6.

Fam