I/O rate limit for volume copy with dd

Currently, volume copy operations consumes disk I/O bandwidth heavily and
may slow down the other guest instances. This patch limits bandwidth for
volume copy to mitigate interference to other instance performance.

In this implementation, 'dd' is put in a blkio cgroup for throttling,
when CONF.volume_copy_bps_limit is set to non-zero.

Change-Id: I32347d2e28842725207a1b3afac7fe137a3fd3b4
Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Implements: blueprint limit-volume-copy-bandwidth
I/O rate limit for volume copy with qemu-img convert

Currently, volume copy operations consumes disk I/O bandwidth heavily and
may slow down the other guest instances. This patch limits bandwidth for
volume copy to mitigate interference to other instance performance.

In this implementation, 'qemu-img' is put in a blkio cgroup for throttling,
when CONF.volume_copy_bps_limit is set to non-zero.

Change-Id: I8403d4bcafc4279654034da97aa9b6c097f9e649
Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Implements: blueprint limit-volume-copy-bandwidth
Minor cleanups in test_volume

Fix incorrect parameter order for mock decorators.  This
just happened to work because they were used in the same way
in test_reserve_volume_success().

Remove incorrect comments.  These seem to mix up 'error' versus
'error_deleting' for expected states -- but the assertEqual args
are sufficiently explanatory by themselves.

Change-Id: I763265b8365d3b2fcece94b14639a1bed7b6a848
Merge "I/O rate limit for volume copy with dd"
Merge "I/O rate limit for volume copy with qemu-img convert"
Merge "Minor cleanups in test_volume"