[Bug 1032550] Re: [multipath] failed to get sysfs information

[Peter Petrakis]

What I really need is a crashdump. I'm simply short on time to reproduce
this myself.

https://wiki.ubuntu.com/Kernel/CrashdumpRecipe

Configure sysctl to panic on oops, that should do it.

This stack section is interesting.
Dec  9 09:18:27 ealxs00195 kernel: [1726974.078795] RIP: 0010:[<ffffffff8165b049>]  [<ffffffff8165b049>] _raw_spin_unlock_irqrestore+0x19/0x30
...
Dec  9 09:18:27 ealxs00195 kernel: [1726974.091694]  [<ffffffff8142f764>] __scsi_remove_target+0xd4/0xf0
Dec  9 09:18:27 ealxs00195 kernel: [1726974.091696]  [<ffffffff8142f841>] scsi_remove_target+0xc1/0xe0
Dec  9 09:18:27 ealxs00195 kernel: [1726974.091701]  [<ffffffffa00deb96>] fc_starget_delete+0x26/0x30 [scsi_transport_fc]
Dec  9 09:18:27 ealxs00195 kernel: [1726974.091706]  [<ffffffff81084b1a>] process_one_work+0x11a/0x480

It's required to be able to sleep in a workq context, we're grabbing spinlocks here, which when done quickly
is fine, but holding them too long and well, you see this. I doubt this is the root cause, something else is likely
holding the locks due to an error handling condition and the removal threads are just victims.

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https://bugs.launchpad.net/bugs/1032550

Title:
  [multipath]  failed to get sysfs information

Status in “multipath-tools” package in Ubuntu:
  In Progress

Bug description:
  when shutdown switch port of host HBA,  multippath-tool can't get
  correct information  of subpath. by check the "multipath" output,
  some storage device type info disapppear and the failed path always
  stay in path group and don't be clear out.


  mpath2 (3600601601c102900944737e4a73fe011) dm-51 ,
  size=6.0G features='1 queue_if_no_path' hwhandler='1 emc' wp=rw
  |-+- policy='round-robin 0' prio=1 status=active
  | |- #:#:#:#  -    #:#     failed faulty running
  | `- 5:0:2:5  sdcu 70:32   active ready running
  `-+- policy='round-robin 0' prio=0 status=enabled
    |- 5:0:3:5  sdfa 129:192 active ready running
    `- #:#:#:#  -    #:#     failed faulty running
  mpath38 (3600601601c1029008eb6dbe8ae3fe011) dm-59 DGC,VRAID
  size=5.0G features='1 queue_if_no_path' hwhandler='1 emc' wp=rw
  |-+- policy='round-robin 0' prio=1 status=active
  | `- 5:0:2:13 sddf 70:208  active ready running
  `-+- policy='round-robin 0' prio=0 status=enabled
    `- 5:0:3:13 sdfk 130:96  active ready running
  mpath63 (360000970000198700131533030303932) dm-13 EMC,SYMMETRIX
  size=5.6G features='0' hwhandler='0' wp=rw
  `-+- policy='round-robin 0' prio=1 status=active
    |- 5:0:0:8  sdl  8:176   active ready running
    `- 5:0:1:8  sdbd 67:112  active ready running
  mpath95 (360000970000198700131533030323445) dm-43 ,
  size=898M features='0' hwhandler='0' wp=rw
  `-+- policy='round-robin 0' prio=1 status=active
    |- #:#:#:#  -    #:#     failed faulty running
    |- #:#:#:#  -    #:#     failed faulty running
    |- 5:0:0:38 sdas 66:192  active ready running
    `- 5:0:1:38 sdck 69:128  active ready running


  Same time, the syslog show many

  ---------------
  Aug  2 18:25:16 Linux51 multipathd: sdht: failed to get sysfs information
  Aug  2 18:25:16 Linux51 multipathd: sdht: unusable path
  ... ...
  ---------------

  After path  recover, all failed path come back without problem.  there
  is no IP blocked and error happend during fail/recover period.

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