** Description changed:

+ [Impact]
+ Multipath users using EMC XtremIO storage as boot device or at install time 
may run into this issue. With the module unavailable the device is more often 
than not unavailable. Any users changing path selector to 'queue-length' with 
other storage devices may also be affected.
+ 
+ [Test case]
+ 1) Install on multipath system using EMC XtremIO storage / OR:
+  a) Start d-i install on qemu with multipath enabled
+  b) exit to d-i menu
+  c) modify /etc/multipath.conf to define path selector as 'queue-length' for 
the local qemu device.
+  d) restart multipathd if necessary.
+ 2) Try to complete the install, setting up storage as multipath and using the 
multipath device as boot disk.
+ 3) Reboot to disk.
+ 
+ In a success case, the install should complete successfully without
+ requiring manual configuration from the user to support the multipath
+ storage past the normal detection of multipath and partitioning.
+ 
+ In a failure case, the install may not complete, or rebooting may fail
+ or lead to a system booted on a single path of the multipath device (ie.
+ / on /dev/sda2 rather than /dev/mpatha2).
+ 
+ [Regression Potential]
+ The inclusion of a new multipath path selector driver should not cause any 
regressions, but any failure to detect, configure or boot on multipath devices 
following this change on XtremIO hardware or otherwise would constitute a 
regression potentially caused by this change.
+ 
+ ---
+ 
  ---Problem Description---
  dm-queue-length module is not included in installer/initramfs
  
  On Ubuntu, multipath devices using the 'queue-length' path selector
  are non-functional on both the installer and initramfs environments;
  because the 'dm-queue-length' kernel module is not included in them.
  
  The multipath-modules.udeb (src:linux) does not include it in the installer,
  nor multipath-tools-boot (src:multipath-tools) installs it in the initramfs.
  
  One example is the EMC XtremIO storage, which has 'queue-length' defined as
  its path selector in the default multipath configuration, at least on 16.04.
  
  Other products may be affected if they are manually configured to use that
  path selector (e.g., via /etc/multipath.conf), and the mere switch of that
  might render the system _unbootable_ if booting from multipath, since the
  initramfs is affected.
  
  More recently this and another storage changed default path selectors out
  of 'queue-length', however, it's virtually possible for any storage system
  to be affected, with the described manual configuration change.  So, this
  change is also desired on for the next stable release, 17.04, and later.
  
  Patches are provided for 16.04 and 17.04.
  
  Error logs in LP comment #6.

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https://bugs.launchpad.net/bugs/1673350

Title:
  dm-queue-length module is not included in installer/initramfs

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