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

[Vladimir Sementsov-Ogievskiy]

29.01.2021 10:35, Roman Kagan wrote:
> 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?

For now reconnect feature is covered only by two tests tests/qemu-iotests/264 
and tests/qemu-iotests/277.

Also note, that since "f203080bbd iotests: rewrite check into python" you should add new 
iotests with human-readable file names into tests/qemu-iotests/tests subdirectory. Also you don't 
need to update tests/qemu-iotests/group file (it's absent now), test groups are defined in tests 
themselves in a comment, like "# group: rw quick".

--
Best regards,
Vladimir