virtio_balloon: don't softlockup on huge balloon changes.
virtio_balloon: don't softlockup on huge balloon changes.

When adding or removing 100G from a balloon:

    BUG: soft lockup - CPU#0 stuck for 22s! [vballoon:367]

We have a wait_event_interruptible(), but the condition is always true
(more ballooning to do) so we don't ever sleep.  We also have a
wait_event() for the host to ack, but that is also always true as QEMU
is synchronous for balloon operations.

Reported-by: Gopesh Kumar Chaudhary <a2338237cf67e5596d184e35d35aede4898bf5f5@in.ibm.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@kernel.org
Signed-off-by: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs