Re: [Nbd] [PATCH 4/4] nbd: add a nbd-control interface
On Wed, Jan 25, 2017 at 03:36:20PM -0600, Eric Blake wrote:
> How do you get an fd to existing nbd block device? Your intent is to
> use an ioctl to request creating/opening a new nbd device that no one
> else is using; opening an existing device in order to send that ioctl
> may have negative ramifications to the actual user of that existing
> device, if not permissions issues that prevent the open from even
> happening. Having a separate control fd makes it obvious that you are
> asking for a new nbd device, and don't want to stomp on any existing
> devices.
Yes, - this whole concept of needing a device first to then associate
it with a backing store is something we had a in a lot of drivers,
and it's always been a major problem. Thus we've been slowly moving
all the drivers off it.
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