On Tue, Feb 28, 2017 at 11:57:11AM -0500, Josef Bacik wrote:

The existing ioctl interface for configuring NBD devices is a bit
cumbersome and hard to extend.  The other problem is we leave a
userspace app sitting in it's syscall until the device disconnects,
which is less than ideal.

True.

On the other hand, it has the advantage that you leave a userspace app
sitting around until the device disconnects, which allows for some form
of recovery in case you're doing root-on-NBD and the server has a
hiccup. Don't underestimate the advantage of that.

(of course, that requires that the return value of NBD_DO_IT makes a
difference between "unexpected connection drop" and "we sent
NBD_CMD_DISC", but that's a different matter entirely)

-- 
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
       people in the world who think they really understand all of its rules,
       and pretty much all of them are just lying to themselves too.
 -- #debian-devel, OFTC, 2016-02-12