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

[Łukasz Zemczak]

Hello Mariusz, or anyone else affected,

Accepted mdadm into bionic-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/mdadm/4.1~rc1-3~ubuntu18.04.2 in a
few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-bionic to verification-done-bionic. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-bionic. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: mdadm (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed-bionic

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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:
  Fix Committed
Status in mdadm source package in Cosmic:
  Fix Committed

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:
         mdadm -CR imsm0 -e imsm -n 2 /dev/sd[bc]
     2. Create IMSM level 0 Array:
         mdadm -CR vol0 -l 0 -n 2 /dev/sd[bc]
     3. Wait for resync to complete
        mdadm --wait /dev/md/vol0
     4. Read /proc/mdstat and check /dev/md/ directory
        cat /proc/mdstat
        ls /dev/md/
     5. Fail one disk incrementaly (simulate device disappearing
        from system)
        mdadm -If sdc
     6. Check mdstat file and /dev/md/
        cat /proc/mdstat
        ls /dev/md/
     Result:
        After disk fail [5] raid 0 array should disappear from mdstat,
        link /dev/md/imsm0 should exist.

  
   * 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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