Bug 1329543

Fix included in qemu-kvm-rhev-2.3.0-31.el7_2.14

Reproduced with:
qemu-kvm-rhev-2.3.0-31.el7_2.11.x86_64
kernel-3.10.0-401.el7.x86_64

Steps:
1. Launch guest:
/usr/libexec/qemu-kvm -cpu host -m 1024 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x6 -drive file=/home/RHEL-Server-7.3-64-virtio.raw,format=raw,if=none,id=drive-virtio-disk0,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-virtio-disk0,id=virtio-disk0 -vnc :1 -monitor stdio -netdev tap,id=hostnet0,vhost=on -device virtio-net-pci,netdev=hostnet0,id=net0,mac=3C:D9:2B:09:AB:44,bus=pci.0,addr=0x4 -qmp tcp:0:5555,server,nowait -drive file=/home/disk1,if=none,id=drive-virtio-disk1,format=qcow2,serial=531fa1b1-fbd0-42ca-9f6b-cf764c91f8a9,cache=none,werror=stop,rerror=stop,aio=threads -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x8,drive=drive-virtio-disk1,id=virtio-disk1 -drive file=/home/disk2,if=none,id=drive-virtio-disk2,format=qcow2,serial=19644ad4-fe32-4b12-8bfb-d75a16fec85a,cache=none,werror=stop,rerror=stop,aio=threads -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0xa,drive=drive-virtio-disk2,id=virtio-disk2 -drive file=/home/disk3,if=none,id=drive-virtio-disk3,format=qcow2,serial=f105f1cc-ab59-4c62-a465-e3ef33886c17,cache=none,werror=stop,rerror=stop,aio=threads -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0xb,drive=drive-virtio-disk3,id=virtio-disk3 -drive file=/home/disk0,if=none,id=drive-virtio-disk4,format=qcow2,serial=f8ebfb39-2ac6-4b87-b193-4204d1854edc,cache=none,werror=stop,rerror=stop,aio=threads -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0xc,drive=drive-virtio-disk4,id=virtio-disk4

2. Generate snapshots with transaction:
{ "execute": "transaction", "arguments": { "actions": [ { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "drive-virtio-disk0",
"snapshot-file": "/home/disk0-sn1", "format": "qcow2" } }, { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "drive-virtio-disk1", "snapshot-file": "/home/disk1-sn1", "format": "qcow2" } }, { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "drive-virtio-disk2", "snapshot-file": "/home/disk2-sn1", "format": "qcow2" } },{ 'type': 'blockdev-snapshot-sync', 'data' : { "device": "drive-virtio-disk3",
"snapshot-file": "/home/disk3-sn1", "format": "qcow2" } }, { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "drive-virtio-disk4", "snapshot-file": "/home/disk4-sn1", "format": "qcow2" } }] } }

3. block stream simultaneously:
{ "execute": "block-stream", "arguments": { "device": "drive-virtio-disk0", "on-error": "report" } }
{"return": {}}
{ "execute": "block-stream", "arguments": { "device": "drive-virtio-disk1", "on-error": "report" } }
{"return": {}}

Result:
qemu hangs for a while until all block job complete.


Verified with:
qemu-kvm-rhev-2.3.0-31.el7_2.14.x86_64
kernel-3.10.0-401.el7.x86_64

Steps:
Same as above.

Results:
qemu does not hang, later job could finished before previous job, and info block could give correct information before all block job complete.

{"timestamp": {"seconds": 1463981812, "microseconds": 379183}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "drive-virtio-disk1", "len": 1073741824, "offset": 1073741824, "speed": 0, "type": "stream"}}
{"timestamp": {"seconds": 1463981996, "microseconds": 325298}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "drive-virtio-disk0", "len": 21474836480, "offset": 21474836480, "speed": 0, "type": "stream"}}

(qemu) info block
drive-virtio-disk0: /home/disk0-sn1 (qcow2)
    Cache mode:       writeback
    Backing file:     /home/RHEL-Server-7.3-64-virtio.raw (chain depth: 1)

drive-virtio-disk1: /home/disk1-sn1 (qcow2)
    Cache mode:       writeback, direct

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2016:1371