[Bug 1457517] Re: Unable to boot from volume when flavor disk too small

[OpenStack Infra]

Reviewed:  https://review.openstack.org/213308
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=8794b938dcb983b7c918718807c2396cb255b4ce
Submitter: Jenkins
Branch:    stable/kilo

commit 8794b938dcb983b7c918718807c2396cb255b4ce
Author: Matthew Booth <mbooth at redhat.com>
Date:   Wed Jul 22 14:56:52 2015 +0100

    Don't check flavor disk size when booting from volume
    
    When creating a volume from an image, cinder copies the image metadata
    into volume properties. When booting from the volume, we read this
    metadata from the volume and use it as image metadata once again.
    
    While fixing the check against min_ram,
    change I861a78b5c7efa71e4bf7206d388b8d0d8048c78e introduced a
    regression which prevents a user from booting a volume which is larger
    than the flavor's disk. As we are not creating this disk, this check
    does not make sense. Similarly, it checks the image metadata's
    min_disk against the flavor disk size, which is not being used.
    
    This change leaves the image metadata check unaltered when creating a
    flavor disk. When booting from a volume, we check min_disk from image
    metadata against the actual size of the volume. We don't check the
    volume size at all. The check against min_ram is retained unaltered.
    
    Closes-Bug: #1457517
    Closes-Bug: #1459491
    Closes-Bug: #1466305
    Change-Id: I264493172da20b664df571e32876030246c2a87c
    (cherry picked from commit 642c986f0636d52a9ba279c87e25082b4aa9b3b8)


** Tags added: in-stable-kilo

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https://bugs.launchpad.net/bugs/1457517

Title:
  Unable to boot from volume when flavor disk too small

Status in OpenStack Compute (nova):
  Fix Committed
Status in nova package in Ubuntu:
  Confirmed

Bug description:
  [Impact]

   * Without the backport, booting from volume requires flavor disk size
  larger than volume size, which is wrong. This patch skips flavor disk
  size checking when booting from volume.

  [Test Case]

   * 1. create a bootable volume
     2. boot from this bootable volume with a flavor that has disk size smaller than the volume size
     3. error should be reported complaining disk size too small
     4. apply this patch
     5. boot from that bootable volume with a flavor that has disk size smaller than the volume size again
     6. boot should succeed

  [Regression Potential]

   * none

  
  Version: 1:2015.1.0-0ubuntu1~cloud0 on Ubuntu 14.04

  I attempt to boot an instance from a volume:

  nova boot --nic net-id=[NET ID] --flavor v.512mb --block-device
  source=volume,dest=volume,id=[VOLUME
  ID],bus=virtio,device=vda,bootindex=0,shutdown=preserve vm

  This results in nova-api raising a FlavorDiskTooSmall exception in the
  "_check_requested_image" function in compute/api.py. However,
  according to [1], the root disk limit should not apply to volumes.

  [1] http://docs.openstack.org/admin-guide-cloud/content/customize-
  flavors.html

  Log (first line is debug output I added showing that it's looking at
  the image that the volume was created from):

  2015-05-21 10:28:00.586 25835 INFO nova.compute.api [req-1fb882c7-07ae-4c2b-86bd-3d174602d0ae f438b80d215c42efb7508c59dc80940c 8341c85ad9ae49408fa25074adba0480 - - -] image: {'min_disk': 0, 'status': 'active', 'min_ram': 0, 'properties': {u'container_format': u'bare', u'min_ram': u'0', u'disk_format': u'qcow2', u'image_name': u'Ubuntu 14.04 64-bit', u'image_id': u'cf0dffef-30ef-4032-add0-516e88048d85', u'libvirt_cpu_mode': u'host-passthrough', u'checksum': u'76a965427d2866f006ddd2aac66ed5b9', u'min_disk': u'0', u'size': u'255524864'}, 'size': 21474836480}
  2015-05-21 10:28:00.587 25835 INFO nova.api.openstack.wsgi [req-1fb882c7-07ae-4c2b-86bd-3d174602d0ae f438b80d215c42efb7508c59dc80940c 8341c85ad9ae49408fa25074adba0480 - - -] HTTP exception thrown: Flavor's disk is too small for requested image.

  Temporary solution: I have special flavor for volume-backed instances so I just set the root disk on those to 0, but this doesn't work if volume are used on other flavors.
  Reproduce: create flavor with 1 GB root disk size, then try to boot an instance from a volume created from an image that is larger than 1 GB.

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