[Bug 1571707] Re: The created partitions can be seen in the system only partly when partitioning 256 FCP devices with multipathing

Dimitri John Ledkov launchpad at surgut.co.uk
Fri May 20 05:39:10 UTC 2016

We have experienced races in bringing up devices and partitions before.

During work on automated preseed I'm not convinced that using echo into
/sys/bus/ccw is sufficient race-free action. Have you considered to
tweak the script to use chzdev tooling? instead of echoing things in
sysfs and/or using chccwdev?

And if using parallel mode, do use active configuration only i.e. chzdev
-a -e options.

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  The created partitions can be seen in the system only partly when
  partitioning 256 FCP devices with multipathing

Status in Ubuntu on IBM z Systems:
Status in multipath-tools package in Ubuntu:

Bug description:
  == Comment: #0 - IRINA YASHINA - 2016-04-15 07:14:54 ==
  During the Limit Testing the script limit.tar.gz was used for partitioning 256 FCP devices,
  a partition per device should be created ("./limit.sh fcp_partition").

  The created partitions can be seen in the system only partly, e.g. 89 instead of 256,
  in /proc/partitions, in /dev/disk/by-path.

  For example, in /dev/disk/by-path for LUN 40244000 there is no
  partition sddq1:

  # ll /dev/disk/by-path | grep 40244000
  lrwxrwxrwx 1 root root    10 Apr 14 22:03 ccw-0.0.1800-fc-0x5005076303135401-lun-0x4024400000000000 -> ../../sddq
  lrwxrwxrwx 1 root root    10 Apr 14 20:58 ccw-0.0.1800-fc-0x5005076303535401-lun-0x4024400000000000 -> ../../sdnv
  lrwxrwxrwx 1 root root    10 Apr 14 20:58 ccw-0.0.1840-fc-0x5005076303135401-lun-0x4024400000000000 -> ../../sdxo
  lrwxrwxrwx 1 root root    11 Apr 14 20:58 ccw-0.0.1840-fc-0x5005076303535401-lun-0x4024400000000000 -> ../../sdahh

  It also can't be seen in the output of "ll /proc/partitions":
  	.	.	.
    71      128    1048576 sddq
    71      144    1048576 sddr
    71      160    1048576 sdds
    71      161    1047552 sdds1
    71      176    1048576 sddt
    71      192    1048576 sddu
    71      193    1047552 sddu1
  	.	.	.

  But fdisk shows that the partition sddq1 was created:

  root at s35lp12:~/limit# fdisk -l | grep /sddq
  Disk /dev/sddq: 1 GiB, 1073741824 bytes, 2097152 sectors
  /dev/sddq1       2048 2097151 2095104 1023M 83 Linux

  The output of the commands 'cat /proc/partitions' and 'fdisk -l' are

  The number of seen partitions in the system after partitioning 256 FCP
  devices is differ from time to time.

  With partitioning 30 FCP devices all the created partitions are
  reflected in the system correctly.

  == Comment: #3 - IRINA YASHINA - 2016-04-18 04:03:40 ==
  Additional info:

  investigations show that the script hangs for 256 FCP disks.
  Incorrect and different number of devices in /proc/partitions and /dev/disk/by-path 
  is the result of this hanging.
  The system may be repaired by using partx and kpartx.

  This problem is connected with parallel execution of commands in the script.
  When parallel execution is removed from the script for partitioning FCP disks,
  then there is no hang and all the data in /proc/partitions and /dev/disk/by-path are correct.

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