[Bug 1551828] Re: kpartx causes kernel oops when NVMe devices is not in blacklist

[Mathieu Trudel-Lapierre]

** Description changed:

+ [Impact]
+ Users expecting to use multipath over NVMe device will notice hangs with any software attempting to use the device-mapper devices (/dev/dm-* or /dev/mapper/mpath*).
+ 
+ [Test case]
+ 1) Setup multipath over nvme. (should not be possible with the patch in)
+ 2) Run kpartx -av /dev/dm-device-mulipath-over-nvme   (will hang without the patch)
+ 
+ [Regression Potential]
+ Minimal. This removes a theoretically valid use case of multipath devices using NVMe disks, which is not technically supported and leads to software hangs (and thus installs will not complete, and setting up multipath over NVMe post-install would hang).
+ This only affects nvme devices; so any storage device using the "nvme" naming would no longer be able to setup multipath even if technical specifications were to change sufficiently to support multipath over NVMe (or if some other device starts using this naming which isn't affected by the same limitations).
+ 
+ 
+ -----
+ 
  When on bare metal uses NVMe devices - kpartx cause kernel oops.
  http://paste.openstack.org/show/488638/
  
  Also any tools which works with disks (e.g. fdisk, lsblk) hangs in D state (uninterruptible sleep) while trying to to read /dev/dm-X.
  This bug is already described and fixed in upstream (http://git.opensvc.com/gitweb.cgi?p=multipath-tools/.git;a=commitdiff;h=5c412e47e589b5325ed7de6cba86d906a671d9df)
  
  I made patches for trusty and xenial versions of multipath-tools.
  Patches which fix issue is in attach.
  Could you apply this patches please, at least for trusty version?

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https://bugs.launchpad.net/bugs/1551828

Title:
  kpartx causes kernel oops when NVMe devices is not in blacklist

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