[Bug 1877617] [NEW] Automatic scans cause instability for cloud use cases

[Ben Swartzlander]

Public bug reported:

When using iSCSI storage underneath cloud applications such as OpenStack
or Kubernetes, the automatic bus scan on login causes problems, because
it results in SCSI disks being registered in the kernel that will never
get cleaned up, and when those disks are eventually deleted off the
server, I/O errors begin to accumulate, eventually slowing down the
whole SCSI subsystem, spamming the kernel log, and causing timeouts at
higher levels such that users are forced to reboot the node to get back
to a usable state.

RedHat discovered this problem more than 3 years ago and fixed it
upstream.

https://bugzilla.redhat.com/show_bug.cgi?id=1422941

I had hoped that Debian would eventually pick up the version in which it
was fixed, but another LTS has gone by without picking up the newer
upstream version, and this is a critical problem, so I propose
backporting the fixes.

The 2 patches that need porting are:
https://github.com/open-iscsi/open-iscsi/pull/40
https://github.com/open-iscsi/open-iscsi/pull/49

These changes have been proven safe by 3 years of soak time in the
RedHat ecosystem, so I don't see much risk to taking them into Ubuntu.
They apply cleanly to the most recent versions of focal, bionic, and
xenial.

** Affects: open-iscsi (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1877617

Title:
  Automatic scans cause instability for cloud use cases

Status in open-iscsi package in Ubuntu:
  New

Bug description:
  When using iSCSI storage underneath cloud applications such as
  OpenStack or Kubernetes, the automatic bus scan on login causes
  problems, because it results in SCSI disks being registered in the
  kernel that will never get cleaned up, and when those disks are
  eventually deleted off the server, I/O errors begin to accumulate,
  eventually slowing down the whole SCSI subsystem, spamming the kernel
  log, and causing timeouts at higher levels such that users are forced
  to reboot the node to get back to a usable state.

  RedHat discovered this problem more than 3 years ago and fixed it
  upstream.

  https://bugzilla.redhat.com/show_bug.cgi?id=1422941

  I had hoped that Debian would eventually pick up the version in which
  it was fixed, but another LTS has gone by without picking up the newer
  upstream version, and this is a critical problem, so I propose
  backporting the fixes.

  The 2 patches that need porting are:
  https://github.com/open-iscsi/open-iscsi/pull/40
  https://github.com/open-iscsi/open-iscsi/pull/49

  These changes have been proven safe by 3 years of soak time in the
  RedHat ecosystem, so I don't see much risk to taking them into Ubuntu.
  They apply cleanly to the most recent versions of focal, bionic, and
  xenial.

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