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[Frank Heimes <1801686@xxxxxxxxxxxxxxxxxx>]

** Changed in: ubuntu-z-systems
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1801686

Title:
  [Ubuntu] qdio: reset old sbal_state flags

Status in Ubuntu on IBM z Systems:
  Fix Released
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Fix Released
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Fix Released
Status in linux source package in Disco:
  Fix Released

Bug description:
  == SRU Justification ==

  Description: qdio: reset old sbal_state flags

  Symptom:
     af_iucv socket using HiperSockets may stall.
  Problem:
     When allocating a new AOB fails, handle_outbound() is
  still capable of transmitting the selected buffer
  (just without async completion).
  But if a previous transfer on this queue slot used
  async completion, its sbal_state flags field is still set
  to QDIO_OUTBUF_STATE_FLAG_PENDING.
  So when the upper layer driver sees this stale flag, it
  expects an async completion that never happens.
  Solution:
     Unconditionally clear the buffer's flags field.

  == Fix ==

  64e03ff72623b8c2ea89ca3cb660094e019ed4ae ("s390/qdio: reset old
  sbal_state flags")

  == Regression Potential ==

  Low, because:
  - s390x only
  - further limited to qeth driver (OSA Express networking)
  - changes are limited to two files and 6 lines
     - arch/s390/include/asm/qdio.h b/arch/s390/include/asm/qdio.h
     - drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
  - error was identified at IBM/customer, fix was created there and tested upfront
  - (changes are upstream in 4.20 (according to bug description,
     but in 4.19 according to 'git tag'),
     hence will make it automatically into 'disco')

  == Test Case ==

  Test case / reproduction:
  Error inject and then simulate out-of-memory situation.

  __________

  Description:  qdio: reset old sbal_state flags

  Symptom:      af_iucv socket using HiperSockets may stall.

  Problem:      When allocating a new AOB fails, handle_outbound() is
                still capable of transmitting the selected buffer
                (just without async completion).
                But if a previous transfer on this queue slot used
                async completion, its sbal_state flags field is still set
                to QDIO_OUTBUF_STATE_FLAG_PENDING.
                So when the upper layer driver sees this stale flag, it
                expects an async completion that never happens.

  Solution:     Unconditionally clear the buffer's flags field.

  Reproduction: Error inject, simulating out-of-memory.

  kernel 4.20
  Upstream-ID:  64e03ff72623b8c2ea89ca3cb660094e019ed4ae

  Canonical , please provide this fix for all Releases in Service....
  Ubuntu 18.10, 18.04 and 16.04

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