Re: [PATCH 0/3] block/nbd: fix crashers in reconnect while migrating

[Roman Kagan <rvkagan@yandex-team.ru>]

On Fri, Jan 29, 2021 at 08:51:39AM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 28.01.2021 23:14, Roman Kagan wrote:
> > During the final phase of migration the NBD reconnection logic may
> > encounter situations it doesn't expect during regular operation.
> > 
> > This series addresses some of them that make qemu crash.  They are
> > reproducible when a vm with a secondary drive attached via nbd with
> > non-zero "reconnect-delay" runs a stress load (fio with big queue depth)
> > in the guest on that drive and is migrated (e.g. to a file), while the
> > nbd server is SIGKILL-ed and restarted every second.
> > 
> > See the individual patches for specific crash conditions and more
> > detailed explanations.
> > 
> > Roman Kagan (3):
> >    block/nbd: only detach existing iochannel from aio_context
> >    block/nbd: only enter connection coroutine if it's present
> >    nbd: make nbd_read* return -EIO on error
> > 
> >   include/block/nbd.h |  7 ++++---
> >   block/nbd.c         | 25 +++++++++++++++++--------
> >   2 files changed, 21 insertions(+), 11 deletions(-)
> > 
> 
> Thanks a lot for fixing!
> 
> Do you have some reproducer scripts? Could you post them or may be add
> an iotest?

I don't have it scripted, just ad hoc command lines.  I'll look into
making up a test.  Can you perhaps suggest what existing test to base
on?

Thanks,
Roman.