Re: [Nbd] [PATCH 4/4] nbd: add a nbd-control interface
> On Jan 21, 2017, at 7:12 AM, Wouter Verhelst <w@...112...> wrote:
>
>> On Fri, Jan 20, 2017 at 04:56:52PM -0500, Josef Bacik wrote:
>> This patch mirrors the loop back device behavior with a few changes. First
>> there is no DEL operation as NBD doesn't get as much churn as loop devices do.
>> Secondly the GET_NEXT operation can optionally create a new NBD device or not.
>> Our infrastructure people want to not allow NBD to create new devices as it
>> causes problems for them in containers. However allow this to be optional as
>> things like the OSS NBD client probably doesn't care and would like to just be
>> given a device to use.
>
> Don't be so sure :-)
>
> I agree that having a control device for NBD is useful and would make
> certain things much easier. If that's added, then I'll move to using
> that as a way to control the device rather than opening a device and
> dealing with it that way. In fact, at some point in the past I did
> suggest something along those ways myself; it's just not happened yet.
>
> Obviously though this would require an intermediate situation in which
> the control master would be available as well as (optionally perhaps)
> the old way where you open a specific device node, so that we don't
> break existing implementations before they've had a chance to follow
> suit.
Sorry I wasn't super clear. This doesn't change anything about how the devices are setup, it just means if you do max_nbds=0 you can dynamically add more as you need them, and you can find unused nbd devices easily instead of making the user specify them. When I get home tonight I'll push my nbd-client patch so you can see how I use it. Thanks,
Josef
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