[Bug 1987387] Comment bridged from LTC Bugzilla

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------- Comment From Alexander.Egorenkov at ibm.com 2022-11-03 04:35 EDT-------
(In reply to comment #16)
> Packaging side, LGTM.
>
> However, I'm a bit skeptical at the patch itself, as it technically removes
> a feature. Do we have an analysis of why it's OK to remove the `block:`
> entries? I'm not too familiar with the ecosystem, so wouldn't it possible to
> have a focal userspace running on an older kernel that still presents the
> old way in its sysfs?

According to what i found,
this was deprecated in 2006 and can be re-enabled again in kernel with
CONFIG_SYSFS_DEPRECATED but then a lot of udev tools will break.

https://elixir.bootlin.com/linux/latest/source/init/Kconfig#L1287
https://cateee.net/lkddb/web-lkddb/SYSFS_DEPRECATED.html

Does s390x support such old kernels ?

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https://bugs.launchpad.net/bugs/1987387

Title:
  [UBUNTU 20.04] zgetdump can not handle multivolume dumps

Status in Ubuntu on IBM z Systems:
  In Progress
Status in s390-tools package in Ubuntu:
  Fix Released
Status in s390-tools-signed package in Ubuntu:
  Fix Released
Status in s390-tools source package in Focal:
  Triaged
Status in s390-tools-signed source package in Focal:
  Triaged

Bug description:
  SRU Justification:
  ==================

  [Impact]

   * The zgetdump tool (as part of the current s390-tools version in focal)
     is not able to handle multi-volume dumps (DASD disk) dumps.

   * While this is rarely needed, it is extremely annoying if one is
     in usually urgent need to use it and it does not work.

   * On s390x systems multi-volume (DASD disk) dumps are pretty common,
     due to usually costly and therefore limited disk resources,
     DASD disks are usually relatively small.

  [Fix]

   * d55b787 d55b787d05eb9bd70f93c36cf859b66b2ad02038 "zgetdump: Fix
  device node determination via sysfs"

  [Test Plan]

   * Have an IBM zSystems LPAR with Ubuntu 20.04 / focal (latest).

   * Have two (or more) additional DASD disks reserved for storing dumps,
     assigned to the system and enabled:
     sudo chzdev -e 0002, 0003
     (Assuming 0001 has Ubuntu 20.04 installed - all 3390 disks).
     Get the block device names using 'lsdasd' - assuming here dasdb, dasdc

   * If needed low-level format these disks:
     sudo dasdfmt -y -b 4096 /dev/dasdb
     sudo dasdfmt -y -b 4096 /dev/dasdc

   * Create one single partition per disk:
     fdisk -a /dev/dasdb
     fdisk -a /dev/dasdc

   * Create an mvdump.conf file that points to the above disks
     sudo vi /etc/mvdump.conf
     ...
     cat /etc/mvdump.conf
     /dev/dasdb1
     /dev/dasdc1

   * Re-write the zipl boot record like this:
     sudo zipl -n -M /etc/mvdump.conf

   * Now ipl the system from the first dump DASD: 0002
     and initiate the DASD dump by:
     1. Stop all CPUs.
     2. Store status on the IPL CPU.
     3. IPL the dump tool on the IPL CPU.

   * Wait until the dump is completed and re-ipl the Ubuntu 20.04 again
  (0001).

   * Without this fix one will see a message like this:
     zgetdump -i /dev/dasdb
     zgetdump: Could not open "/sys/bus/ccw/devices/0.0.0002/dasdb/dev" (No such file or directory)

   * With the fix one will see a message like this:
     zgetdump -i /dev/dasdb
     General dump info:
       Dump format........: s390mv_ext
       Version............: 1
       Dump created.......: 
       ...
       Dump device info:
         Volume 0: 0.0.0002 (online/active)
         Volume 1: 0.0.0003 (online/valid)

   * For more in-depth details see the
     'Linux on System z. Using the Dump Tools.' documentation:
     https://www.ibm.com/docs/en/linux-on-systems?topic=dump-hmc-se-example

  [Where problems could occur]

   * A new function got introduced to 'check whether a device with a given
     busid is online'.
     Issues could occur in case this function is broken and 
     checks for a wrong busid, has a wrong path
     or handled the status wrongly.

   * The kind of 'little' refactoring of that patch may lead to
     further unexpected issues (that can largely identified by a test build).

   * The additional use of libutil functions may cause issues
     in case of an outdated libutil that does not offer all needed functions.
     (Testable with a test build.)

   * Erroneous code may even break single volume dumps

  [Other Info]
   
   * This code is known to work with hirsute and newer Ubuntu releases,
     esp. jammy (respectively their s390-tools versions).

   * The upstream code can be cleanly cherry-picked,
     hence is applied as-is.

   * An updated s390-tools version 2.12.0-0ubuntu3.7 with a
     patched zgetdump tool was build and made available via this PPA:
     https://launchpad.net/~fheimes/+archive/ubuntu/lp1987387
     and was already successfully tested!
  __________

  == Comment: #0 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2022-08-16 12:40:46 ==
  I installed Ubuntu 20.04.4 LTS on IBM z14, enabled two DASDs, created one partition on each DASD and created an mvdump.conf file like this:
  /dev/dasdc1
  /dev/dasdd1

  I wrote the boot record by zipl -n -M mvdump.conf and IPLed the system from dasdc devno.
  The dump completed succesfully.
  Then I tried to get this dump via zgetdump on the restarted Ubuntu 20.04.4 system (zgetdump -v reports version 2.12.0-build-20220506), I got the following error:
  root at m8330032:~# zgetdump -i /dev/dasdc
  zgetdump: Could not open "/sys/bus/ccw/devices/0.0.9405/dasdc/dev" (No such file or directory)
  root at m8330032:~# zgetdump -i /dev/dasdc1
  zgetdump: Could not open "/sys/bus/ccw/devices/0.0.9405/dasdc/dev" (No such file or directory)
  root at m8330032:~# zgetdump -i /dev/dasdd
  zgetdump: Could not open "/sys/bus/ccw/devices/0.0.9405/dasdc/dev" (No such file or directory)
  root at m8330032:~# zgetdump -i /dev/dasdd1
  zgetdump: No valid dump found on "/dev/dasdd1"
  root at m8330032:~#

  However, If I'm doing the same zgetdump on another system (e.g. with newer s390-tools version), I get the expected result
  m83lp32:~ # zgetdump -i /dev/dasdc
  General dump info:
    Dump format........: s390mv_ext
    Version............: 1
    Dump created.......: Tue, 16 Aug 2022 18:31:57 +0200
    Dump ended.........: Tue, 16 Aug 2022 18:32:02 +0200
    Dump CPU ID........: ff1fa1e739068000
    UTS node name......: m8330032.lnxne.boe
    UTS kernel release.: 5.4.0-124-generic
    UTS kernel version.: #140-Ubuntu SMP Thu Aug 4 02:23:07 UTC 2022
    Build arch.........: s390x (64 bit)
    System arch........: s390x (64 bit)
    CPU count (online).: 16
    CPU count (real)...: 16
    Dump memory range..: 4096 MB
    Real memory range..: 4096 MB
    Dump file size.....: 849 MB

  Memory map:
    0000000000000000 - 00000000ffffffff (4096 MB)

  Dump device info:
    Volume 0: 0.0.9405 (online/active)
    Volume 1: 0.0.9406 (online/valid)
  m83lp32:~ #

  The error is easily reproducible.
  Please update zgetdump to a newer version to solve this RAS problem.

  With Jammy (22.04.1; s390-tools version 2.20.0-build-20220623) this
  problem does not occur.

  == Comment: #3 - Jan Hoeppner <Jan.Hoeppner at de.ibm.com> - 2022-08-22 01:43:45 ==
  There were several issues fixed in s390-tools v2.15.1 in regards to multivolume dumps: https://github.com/ibm-s390-linux/s390-tools/releases/tag/v2.15.1

  Especially the following upstream commit for zgetdump:
  https://github.com/ibm-s390-linux/s390-tools/commit/d55b787d05eb9bd70f93c36cf859b66b2ad02038

  ---
  External link: https://warthogs.atlassian.net/browse/PEI-30

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