[Bug 1811795] Re: Mdadm: external metadata arrays and containers are removed incorrectly

[Christian Ehrhardt ]

Incomplete waiting for PAP verification and better test steps

** Changed in: mdadm (Ubuntu Cosmic)
       Status: New => Incomplete

** Changed in: mdadm (Ubuntu Bionic)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1811795

Title:
  Mdadm: external metadata arrays and containers are removed incorrectly

Status in mdadm package in Ubuntu:
  Fix Released
Status in mdadm source package in Bionic:
  Incomplete
Status in mdadm source package in Cosmic:
  Incomplete

Bug description:
  [Impact]

   * The response to device fails so far was to remove underlying 
     containers. That failed if the device itself was not stopped
     before doing so causing issues.

   * Fix by backporting upstream fix

  [Test Case]

   * This needs a Intel(R) Matrix Storage Hardware which limits the 
     systems this can be tested.
     1. Create IMSM container on 2 SATA disks.
     2. Create R0 IMSM volume
     3. Wait for resync to complete.
     4. Fail one of disks

   * these should allow someone who is not familiar with the affected
     package to reproduce the bug and verify that the updated package fixes
     the problem.

  [Regression Potential]

   * The patch changes the behavior on removing devices. So in that use-case 
     lies the potential to regress somebody.
     It adds stopping the device before removing the containers associated 
     to it (that is the fix). OTOH if there are cases where the kernel 
     signals a device fail it would formerly not have removed it (the bug) 
     but there are (very low) chances that somebody relies on that behavior.
     Since this avoids I/O errors on partially removed device elements I'd 
     expect taking the change makes it better overall.

  [Other Info]
   
   * n/a

  ---

  Steps to reproduce:

  1. Create IMSM container on 2 SATA disks.

  2. Create R0 IMSM volume

  3. Wait for resync to complete.

  4. Fail one of disks

  Expected result:
  R0 Array should disappear form /proc/mdstat.

  Actual result:
  R0 array is visible in mdstat, link to container in /dev/md/ is removed.

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