On Mon, Jan 23, 2017 at 10:03 AM, Greg KH
<gregkh@xxxxxxxxxxxxxxxxxxx>
wrote:
> On Mon, Jan 23, 2017 at 09:57:52AM -0500, Josef Bacik wrote:
> > On Mon, Jan 23, 2017 at 9:52 AM, Greg KH
> > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > On Mon, Jan 23, 2017 at 09:42:08AM -0500, Josef Bacik wrote:
> > > >
> > > >
> > > > On Sat, Jan 21, 2017 at 4:05 AM, Greg KH
> > > > <gregkh@xxxxxxxxxxxxxxxxxxx> 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.
> > > > > >
> > > > > > Signed-off-by: Josef Bacik <jbacik@xxxxxx>
> > > > >
> > > > > A random char device with odd ioctls? Why? There's no
other
> > > > > configuration choice you could possibly use? Where is
the
> > > > userspace
> > > > > tool that uses this new kernel api?
> > > > >
> > > > > You aren't passing in structures to the ioctl, so why
does
> > this
> > > > HAVE to
> > > > > be an ioctl?
> > > >
> > > > Again, this is how loop does it so I assumed a known,
regularly
> > > > used API was
> > > > the best bet. I can do literally anything, but these
> > interfaces
> > > > have to be
> > > > used by other people, including internal people. The
> > > > /dev/whatever-control
> > > > is a well established way for interacting with dynamic
device
> > > > drivers (loop,
> > > > DM, btrfs), so that's what I went with. Thanks,
> > >
> > > Again, please don't duplicate what loop did, we must _learn_
from
> > > history, not repeat it :(
> >
> > Sure but what am I supposed to do? Have some random sysfs
knobs?
> > Thanks,
>
> It all depends on what you are trying to do. I have yet to
figure that
> out at all here :(
I explained it in the changelog and my response to Wouter. NBD
preallocates
all of its /dev/nbd# devices at modprobe time, so there's no way to
add new
devices as we need them.
