[Bug 1434261] Re: udev keeps a lock on devices while multipath-tools runs in initramfs

[Mathieu Trudel-Lapierre]

Solution appears to be running udevadm settle before calling multipath
-v0 and kpartx, which appears to have positive results on QEMU, and no
adverse effects on systems where the multipath setup is already
returning successfully.

** Changed in: multipath-tools (Ubuntu)
       Status: New => In Progress

** Changed in: multipath-tools (Ubuntu)
   Importance: Undecided => Medium

** Changed in: multipath-tools (Ubuntu)
     Assignee: (unassigned) => Mathieu Trudel-Lapierre (mathieu-tl)

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https://bugs.launchpad.net/bugs/1434261

Title:
  udev keeps a lock on devices while multipath-tools runs in initramfs

Status in multipath-tools package in Ubuntu:
  In Progress

Bug description:
  It appears that multipath-tools has issues running its script
  (detecting multipath devices, then running kpartx to pick up
  partitions, which in turn will also trigger a new run of udev rules
  evaluation) because udev may not always be done with settling and
  evaluating rules by the time the local-top/multipath script gets run.

  This happens because some devices take a while to be detected, which
  also causes the settling to take some time. Before running multipath
  -v0 or kpartx, which will also trigger udev to do work, we should make
  sure udev has released the locks it may have on those devices, since
  multipath will attempt to get an exclusive lock on them too.

  This can be easily reproduced in QEMU multipath installs: booting
  after installation will take a long time, and the resulting boot will
  not always be started with the multipath device
  (/dev/mapper/mpath[0-9]+(-part[0-9]+)?) but may instead be using the
  first single drive it found matching the proper UUID. (see also bug
  1429327)

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