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

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH 0/3] block/nbd: fix crashers in reconnect while migrating
Date: Fri, 29 Jan 2021 08:51:39 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1

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 

Best regards,

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