Hi,
Am 22.04.25 um 13:51 schrieb Alexandre Derumier via pve-devel:
> This is needed for external snapshot live commit,
> when the top blocknode is not the fmt-node.
> (in our case, the throttle-group node is the topnode)
>
> Signed-off-by: Alexandre Derumier <alexandre.derum...@groupe-cyllene.com>
I looked into this again and maybe we can avoid this patch. I think all
you need is to specify the 'top-node' when issuing the commit command.
Without specifying "top-node":
> [I] root@pve8a1 ~# cat block-commit.sh
> #!/bin/bash
> rm -f /tmp/backing.qcow2
> rm -f /tmp/top.qcow2
> qemu-img create /tmp/backing.qcow2 -f qcow2 64M
> qemu-img create /tmp/top.qcow2 -f qcow2 64M
> qemu-system-x86_64 --qmp stdio \
> --nodefaults \
> --object throttle-group,id=thrgr0 \
> --blockdev
> qcow2,node-name=backing0,file.driver=file,file.filename=/tmp/backing.qcow2 \
> --blockdev
> throttle,node-name=drive-scsi0,throttle-group=thrgr0,file.driver=qcow2,file.node-name=node0,file.file.driver=file,file.file.filename=/tmp/top.qcow2,file.backing=backing0
> \
> --device 'virtio-scsi-pci,id=virtioscsi0,bus=pci.0,addr=0x2' \
> --device
> 'scsi-hd,bus=virtioscsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0'
> \
> <<EOF
> {"execute": "qmp_capabilities"}
> {"execute": "query-block"}
> {"execute": "block-commit", "arguments": { "device": "drive-scsi0",
> "base-node": "backing0", "job-id": "commit0" } }
> {"execute": "block-job-complete", "arguments": {"device": "commit0" } }
> {"execute": "query-block"}
> {"execute": "quit"}
> EOF
The result will be:
> {
> "return": [
> {
> "io-status": "ok",
> "device": "",
> "locked": false,
> "removable": false,
> "inserted": {
> "iops_rd": 0,
> "detect_zeroes": "off",
> "image": {
> "virtual-size": 67108864,
> "filename": "/tmp/backing.qcow2",
> "cluster-size": 65536,
> "format": "qcow2",
> "actual-size": 200704,
> "format-specific": {
> "type": "qcow2",
> "data": {
> "compat": "1.1",
> "compression-type": "zlib",
> "lazy-refcounts": false,
> "refcount-bits": 16,
> "corrupt": false,
> "extended-l2": false
> }
> },
> "dirty-flag": false
> },
> "iops_wr": 0,
> "ro": false,
> "node-name": "backing0",
> "backing_file_depth": 0,
> "drv": "qcow2",
> "iops": 0,
> "bps_wr": 0,
> "write_threshold": 0,
> "encrypted": false,
> "bps": 0,
> "bps_rd": 0,
> "cache": {
> "no-flush": false,
> "direct": false,
> "writeback": true
> },
> "file": "/tmp/backing.qcow2"
> },
> "qdev": "scsi0",
> "type": "unknown"
> }
> ]
> }
So no throttle group, bad.
But setting "top-node" being the throttle node like here:
> #!/bin/bash
> rm -f /tmp/backing.qcow2
> rm -f /tmp/top.qcow2
> qemu-img create /tmp/backing.qcow2 -f qcow2 64M
> qemu-img create /tmp/top.qcow2 -f qcow2 64M
> qemu-system-x86_64 --qmp stdio \
> --nodefaults \
> --object throttle-group,id=thrgr0 \
> --blockdev
> qcow2,node-name=backing0,file.driver=file,file.filename=/tmp/backing.qcow2 \
> --blockdev
> throttle,node-name=drive-scsi0,throttle-group=thrgr0,file.driver=qcow2,file.node-name=node0,file.file.driver=file,file.file.filename=/tmp/top.qcow2,file.backing=backing0
> \
> --device 'virtio-scsi-pci,id=virtioscsi0,bus=pci.0,addr=0x2' \
> --device
> 'scsi-hd,bus=virtioscsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0'
> \
> <<EOF
> {"execute": "qmp_capabilities"}
> {"execute": "query-block"}
> {"execute": "block-commit", "arguments": { "device": "drive-scsi0",
> "top-node": "node0", "base-node": "backing0", "job-id": "commit0" } }
> {"execute": "block-job-complete", "arguments": {"device": "commit0" } }
> {"execute": "query-block"}
> {"execute": "quit"}
> EOF
The result will be:
> {
> "return": [
> {
> "io-status": "ok",
> "device": "",
> "locked": false,
> "removable": false,
> "inserted": {
> "iops_rd": 0,
> "detect_zeroes": "off",
> "image": {
> "backing-image": {
> "virtual-size": 67108864,
> "filename": "/tmp/backing.qcow2",
> "cluster-size": 65536,
> "format": "qcow2",
> "actual-size": 200704,
> "format-specific": {
> "type": "qcow2",
> "data": {
> "compat": "1.1",
> "compression-type": "zlib",
> "lazy-refcounts": false,
> "refcount-bits": 16,
> "corrupt": false,
> "extended-l2": false
> }
> },
> "dirty-flag": false
> },
> "virtual-size": 67108864,
> "filename": "json:{\"throttle-group\": \"thrgr0\", \"driver\":
> \"throttle\", \"file\": {\"driver\": \"qcow2\", \"file\": {\"driver\":
> \"file\", \"filename\": \"/tmp/backing.qcow2\"}}}",
> "cluster-size": 65536,
> "format": "throttle",
> "actual-size": 200704,
> "dirty-flag": false
> },
> "iops_wr": 0,
> "ro": false,
> "node-name": "drive-scsi0",
> "backing_file_depth": 1,
> "drv": "throttle",
> "iops": 0,
> "bps_wr": 0,
> "write_threshold": 0,
> "encrypted": false,
> "bps": 0,
> "bps_rd": 0,
> "cache": {
> "no-flush": false,
> "direct": false,
> "writeback": true
> },
> "file": "json:{\"throttle-group\": \"thrgr0\", \"driver\":
> \"throttle\", \"file\": {\"driver\": \"qcow2\", \"file\": {\"driver\":
> \"file\", \"filename\": \"/tmp/backing.qcow2\"}}}"
> },
> "qdev": "scsi0",
> "type": "unknown"
> }
> ]
> }
I hope this is what you want?
Probably QEMU does not consider throttle groups when automatically
determining the top-node, so we need to specify it explicitly.
Best Regards,
Fiona
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