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[Bug 1594377] [NEW] resize does not resize ephemeral disks

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Public bug reported:

Nova resize does not resize ephemeral disks. I have tested this with the
default qcow2 backend, but I expect it to be true for all backends.

I have created 2 flavors:

| OS-FLV-DISABLED:disabled   | False  |
| OS-FLV-EXT-DATA:ephemeral  | 1      |
| disk                       | 1      |
| extra_specs                | {}     |
| id                         | test-1 |
| name                       | test-1 |
| os-flavor-access:is_public | True   |
| ram                        | 256    |
| rxtx_factor                | 1.0    |
| swap                       | 1      |
| vcpus                      | 1      |

and:

| OS-FLV-DISABLED:disabled   | False  |
| OS-FLV-EXT-DATA:ephemeral  | 2      |
| disk                       | 2      |
| extra_specs                | {}     |
| id                         | test-2 |
| name                       | test-2 |
| os-flavor-access:is_public | True   |
| ram                        | 512    |
| rxtx_factor                | 1.0    |
| swap                       | 2      |
| vcpus                      | 2      |

I boot an instance with flavor test-1 with:

$ nova boot --flavor test-1 --image cirros foo

It creates instance directory 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c
containing (amongst non-disk files) disk, disk.eph0, disk.swap, and
disk.config. disk.config is not relevant here.

I check the sizes of each of these disks:

instances]$ for disk in disk disk.eph0 disk.swap; do qemu-img info
3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/$disk; done

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 10M
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/1ba6fbdbe52377ff7e075c3317a48205ac6c28c4
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.eph0
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 324K
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/ephemeral_1_40d1d2c
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.swap
file format: qcow2
virtual size: 1.0M (1048576 bytes)
disk size: 196K
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/swap_1
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

I resize foo with:

$ nova resize foo test-2 --poll

I check the sizes again:

instances]$ for disk in disk disk.eph0 disk.swap; do qemu-img info
3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/$disk; done

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk
file format: qcow2
virtual size: 2.0G (2147483648 bytes)
disk size: 26M
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/1ba6fbdbe52377ff7e075c3317a48205ac6c28c4
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.eph0
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 384K
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/ephemeral_1_40d1d2c
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.swap
file format: qcow2
virtual size: 2.0M (2097152 bytes)
disk size: 196K
cluster_size: 65536
backing file: /home/mbooth/data/nova/instances/_base/swap_2
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

Note that the root and swap disks have been resized, but the ephemeral
disk has not. This is caused by 2 bugs.

Firstly, there is some code in finish_migration in the libvirt driver
which purports to resize disks. This code is actually a no-op, because
disk resizing has already been done by _create_image, which called
cache() with the correct size, and therefore did the resizing. However,
as noted in a comment, the no-op code would not have covered our
ephemeral disk anyway, as it only loops over 'disk.local', which is the
legacy disk naming.

Secondly, _create_image does not iterate over ephemeral disks at all
when called by finish_migration, because finish_migration explicitly
passes block_device_info=None.

** Affects: nova
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Yahoo!
Engineering Team, which is subscribed to OpenStack Compute (nova).
https://bugs.launchpad.net/bugs/1594377

Title:
  resize does not resize ephemeral disks

Status in OpenStack Compute (nova):
  New

Bug description:
  Nova resize does not resize ephemeral disks. I have tested this with
  the default qcow2 backend, but I expect it to be true for all
  backends.

  I have created 2 flavors:

  | OS-FLV-DISABLED:disabled   | False  |
  | OS-FLV-EXT-DATA:ephemeral  | 1      |
  | disk                       | 1      |
  | extra_specs                | {}     |
  | id                         | test-1 |
  | name                       | test-1 |
  | os-flavor-access:is_public | True   |
  | ram                        | 256    |
  | rxtx_factor                | 1.0    |
  | swap                       | 1      |
  | vcpus                      | 1      |

  and:

  | OS-FLV-DISABLED:disabled   | False  |
  | OS-FLV-EXT-DATA:ephemeral  | 2      |
  | disk                       | 2      |
  | extra_specs                | {}     |
  | id                         | test-2 |
  | name                       | test-2 |
  | os-flavor-access:is_public | True   |
  | ram                        | 512    |
  | rxtx_factor                | 1.0    |
  | swap                       | 2      |
  | vcpus                      | 2      |

  I boot an instance with flavor test-1 with:

  $ nova boot --flavor test-1 --image cirros foo

  It creates instance directory 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c
  containing (amongst non-disk files) disk, disk.eph0, disk.swap, and
  disk.config. disk.config is not relevant here.

  I check the sizes of each of these disks:

  instances]$ for disk in disk disk.eph0 disk.swap; do qemu-img info
  3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/$disk; done

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk
  file format: qcow2
  virtual size: 1.0G (1073741824 bytes)
  disk size: 10M
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/1ba6fbdbe52377ff7e075c3317a48205ac6c28c4
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.eph0
  file format: qcow2
  virtual size: 1.0G (1073741824 bytes)
  disk size: 324K
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/ephemeral_1_40d1d2c
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.swap
  file format: qcow2
  virtual size: 1.0M (1048576 bytes)
  disk size: 196K
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/swap_1
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  I resize foo with:

  $ nova resize foo test-2 --poll

  I check the sizes again:

  instances]$ for disk in disk disk.eph0 disk.swap; do qemu-img info
  3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/$disk; done

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk
  file format: qcow2
  virtual size: 2.0G (2147483648 bytes)
  disk size: 26M
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/1ba6fbdbe52377ff7e075c3317a48205ac6c28c4
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.eph0
  file format: qcow2
  virtual size: 1.0G (1073741824 bytes)
  disk size: 384K
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/ephemeral_1_40d1d2c
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  image: 3fab0565-2eb1-4fd9-933b-4e1d80b1b18c/disk.swap
  file format: qcow2
  virtual size: 2.0M (2097152 bytes)
  disk size: 196K
  cluster_size: 65536
  backing file: /home/mbooth/data/nova/instances/_base/swap_2
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

  Note that the root and swap disks have been resized, but the ephemeral
  disk has not. This is caused by 2 bugs.

  Firstly, there is some code in finish_migration in the libvirt driver
  which purports to resize disks. This code is actually a no-op, because
  disk resizing has already been done by _create_image, which called
  cache() with the correct size, and therefore did the resizing.
  However, as noted in a comment, the no-op code would not have covered
  our ephemeral disk anyway, as it only loops over 'disk.local', which
  is the legacy disk naming.

  Secondly, _create_image does not iterate over ephemeral disks at all
  when called by finish_migration, because finish_migration explicitly
  passes block_device_info=None.

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