nbd: on-the-fly resize does not work any more

[Mykola Golub]

Hi,

It looks like after the recent changes to nbd driver, on-the-fly
resize has stopped working for rbd-nbd. Particularly this change [1]
breaks how NBD_SET_SIZE is used for rbd-nbd on-the-fly resize [2].

Could this be fixed?

[1] https://github.com/torvalds/linux/commit/639812a1ed9bf49ae2c026086fbf975339cd1eef
[2] https://github.com/ceph/ceph/blob/483f14c/src/tools/rbd_nbd/rbd-nbd.cc#L488

-- 
Mykola Golub