no swap if block-device-mapping of /dev/vdb=swap

[Scott Moser]

Assuming:
  nova-manage instance_type create --flavor=0 --memory=512 --local_gb=2 --swap=512 --cpu=1 --name "m1.xsmall"

Running m1.xsmall instances like the following yeilds the given output:
A. <no block device mappings>
   md: { ami: vda, root: /dev/vda, ephemeral0: /dev/vdb, swap: /dev/vdc }
   disks: vda, vdb(ephemeral0), vdc(swap)
B. /dev/vdb=swap /dev/vdc=ephemeral0
   md: { ami: vda, root: /dev/vda, ephemeral0: /dev/vdc }
   disks: vdb(ephemeral0)
C. /dev/vdc=ephemeral0
   md: { ami: vda, root: /dev/vda, ephemeral0: /dev/vdc }
   disks: vda, vdb(ephemeral0)
D. /dev/vdb=ephemeral0
   md: { ami: vda, root: /dev/vda, swap: /dev/vdc, ephemeral0: /dev/vdb }
   disks: vda, vdb(ephemeral0), vdc(swap)
E. /dev/vdb=ephemeral0 /dev/vdc=swap
   md: { ami: vda, root: /dev/vda, ephemeral0: /dev/vdb, swap: /dev/vdc }
   disks: vda, vdb(ephemeral0), vdc(swap)

Above 'md' means data pulled from the instance's metadata service, 'disks' are disks actually seen to the instance.

Basically, above, if you specify swap "wrong", then you just lose it.

This is a low priority issue really. The user just needs to know that if the instance-type has swap, and they want to use it, they have to specify block device mappings correctly or not at all.

[Isaku Yamahata (yamahata)]

Case B seems a bug. However other case seem correct according as the device is overriden.