Cloning to RHEL 7

+++ This bug was initially created as a clone of Bug #1119385 +++

Cloning to RHEL 6 - 'virsh blockcopy' is not obeying its docs.

+++ This bug was initially created as a clone of Bug #1119173 +++

Description of problem:
http://libvirt.org/html/libvirt-libvirt.html#virDomainBlockJobAbort

The API virDomainBlockJobAbort should be sync default. But with VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT flag, the api is async, not sync.


    if (disk->mirror && mode == BLOCK_JOB_ABORT &&
        (flags & VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT)) {
        ret = qemuDomainBlockPivot(conn, driver, vm, device, disk);
        goto endjob;
    }

After called qemuDomainBlockPivot, the code goto the endjob. That skip the
block simulation code.

Version-Release number of selected component (if applicable):
Trunk code

How reproducible:


Steps to Reproduce:
1. virDomainBlockRebase with VIR_DOMAIN_BLOCK_REBASE_COPY flag
2. virDomainBlockJobAbort with VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT flag


Actual results:
virDomainBlockJobAbort is async

Expected results:
virDomainBlockJobAbort is sync

Additional info:

--- Additional comment from Peter Krempa on 2014-07-14 02:37:40 MDT ---

From what I understand, the "block-job-complete" qmp command called by qemuDomainBlockPivot() is inherently synchronous and thus we don't need to simulate the blocking of the API.

--- Additional comment from Xu He Jie on 2014-07-14 07:13:26 MDT ---

From this test code http://git.qemu.org/?p=qemu.git;a=blob_plain;f=tests/qemu-iotests/041;hb=HEAD to see, the block-job-complete is async. Even if you are right 'block-job-complete' is sync, that also means VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC flag doesn't work.

--- Additional comment from Eric Blake on 2014-07-14 09:59:54 MDT ---

Blech.  qemu's block-job-complete is inherently async - it merely requests the end of a job and returns control immediately; but the job may take a while longer to actually end because of time spent flushing sectors to disk.  Looks like I introduced the bug when adding blockcopy in commit eaba79d, and that I merely need to update where the goto jumps.

--- Additional comment from Eric Blake on 2014-07-14 10:10:03 MDT ---

We've explicitly documented that the VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC flag can, but not must, return control before the job has actually ended.  Ignoring the async flag is not a problem. But when the flag is not present, and we have promised sync behavior, then libvirt does need to wait for the event.

--- Additional comment from Eric Blake on 2014-07-14 10:24:23 MDT ---

Upstream patch proposed:
https://www.redhat.com/archives/libvir-list/2014-July/msg00664.html