[Bug 1747044] Re: kpartx 0.7.4-2ubuntu1 in bionic does not remove loop devices

[Francis Ginther]

I have a more concise method for showing this problem. When I try to
mount the partitions in an img file with kpartx 0.7.4-2ubuntu1, it
silently fails:

# First, fetch an image
$ wget https://cloud-images.ubuntu.com/bionic/20180124/bionic-server-cloudimg-amd64.img
...
$ sudo kpartx -v -l bionic-server-cloudimg-amd64.img 
loop deleted : /dev/loop0
$ sudo kpartx -v -s -a bionic-server-cloudimg-amd64.img 
$ ll /dev/mapper/
total 0
drwxr-xr-x  2 root root      60 Feb  2 20:03 ./
drwxr-xr-x 16 root root    3580 Feb  2 20:03 ../
crw-------  1 root root 10, 236 Feb  2 20:03 control


The same works with 0.6.4-5ubuntu1 (and it can even delete the loop device):

$ sudo kpartx -v -l bionic-server-cloudimg-amd64.img 
loop0p1 : 0 598525 /dev/loop0 3
loop deleted : /dev/loop0
$ sudo kpartx -v -s -a bionic-server-cloudimg-amd64.img
add map loop0p1 (253:0): 0 598525 linear 7:0 3
$ ll /dev/mapper
total 0
drwxr-xr-x  2 root root      80 Feb  2 20:08 ./
drwxr-xr-x 16 root root    3600 Feb  2 20:08 ../
crw-------  1 root root 10, 236 Feb  2 20:04 control
lrwxrwxrwx  1 root root       7 Feb  2 20:08 loop0p1 -> ../dm-0

$ sudo kpartx -v -d bionic-server-cloudimg-amd64.img 
del devmap : loop0p1
loop deleted : /dev/loop0
$ ll /dev/mapper
total 0
drwxr-xr-x  2 root root      60 Feb  2 20:13 ./
drwxr-xr-x 16 root root    3580 Feb  2 20:13 ../
crw-------  1 root root 10, 236 Feb  2 20:04 control

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https://bugs.launchpad.net/bugs/1747044

Title:
  kpartx 0.7.4-2ubuntu1 in bionic does not remove loop devices

Status in multipath-tools package in Ubuntu:
  New

Bug description:
  We're seeing a problem now when running livecd-rootfs in bionic with
  kpartx from 0.7.4-2ubuntu1. The issue appears to be the result in a
  change in kpartx, as a result, the /dev/loop devices are not getting
  deleted. The best data I have from this so far is a comparison between
  old and current build logs. The old logs showed:

  ++ kpartx -v -d binary/boot/disk-uefi.ext4
  + kpartx_stdout='del devmap : loop0p15
  del devmap : loop0p14
  del devmap : loop0p1
  loop deleted : /dev/loop0'
  + echo 'del devmap : loop0p15
  del devmap : loop0p14
  del devmap : loop0p1
  loop deleted : /dev/loop0'

  Thew new logs show:

  ++ kpartx -v -d binary/boot/disk-uefi.ext4
  + kpartx_stdout=
  + echo ''

  The code being run is from the 'functions' in lp:livecd-rootfs. In the
  current runs, kpartx_stdout is an empty string:

  clean_loops() {
      local kpartx_ret
      local kpartx_stdout

      if [ -n "${backing_img}" ]; then
          # sync before removing loop to avoid "Device or resource busy" errors
          sync
          kpartx_ret=""
          kpartx_stdout=$(kpartx -v -d "${backing_img}") || kpartx_ret=$?
          echo "$kpartx_stdout"
          if [ -n "$kpartx_ret" ]; then
              if echo "$kpartx_stdout" | grep -q "loop deleted"; then
                  echo "Suppressing kpartx returning error (#860894)"
              else
                  exit $kpartx_ret
              fi
          fi
          unset backing_img
      fi

      if [ -z "${rootfs_dev_mapper}" ]; then
          return 0
      fi

      unset loop_device
      unset loop_raw
      unset rootfs_dev_mapper
  }

  I am doing some further debugging on this and am trying to reproduce
  this outside of launchpad. I am not able to post a full build log. But
  I can probably post a longer 'sanitized' bit.

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