[PATCH 00/12] nbd: Netlink interface and path failure enhancements

[Josef Bacik <josef@toxicpanda.com>]

This patchset adds a new netlink configuration interface to NBD as well as a
bunch of enhancments around path failures.  The patches provide the following
enhancemnts to NBD

 - Netlink configuration interface that doesn't leave a userspace application
   waiting in kernel space for the device to disconnect.
 - Netlink reconfigure interface for adding re-connected sockets to replace dead
   sockets.
 - A flag to destroy the NBD device on disconnect, much like how mount -o loop
   works.
 - A status interface that currently will only report whether a device is
   connected or not, but can be extended to include whatever in the future.
 - A netlink multicast notification scheme to notify user space when there are
   connection issues to allow for seamless reconnects.
 - Dead link handling.  You can specify a dead link timeout and the NBD device
   will pause IO for that timeout waiting to see if the connection can be
   re-established.  This is helpful to allow for things like nbd server upgrades
   where the whole server disappears for a short period of time.

These patches have been thorougly and continuously tested for about a month.
I've been finding bugs in various places, but this batch has been solid for the
last few days of testing, which include a constant disconnect/reconnect torture
test.  Thanks,

Josef