Max Reitz <mre...@redhat.com> writes: > On 13.11.19 14:24, Sergio Lopez wrote: >> >> Sergio Lopez <s...@redhat.com> writes: >> >>> no-re...@patchew.org writes: >>> >>>> Patchew URL: >>>> https://patchew.org/QEMU/20191112113012.71136-1-...@redhat.com/ >>>> >>>> >>>> >>>> Hi, >>>> >>>> This series failed the docker-quick@centos7 build test. Please find the >>>> testing commands and >>>> their output below. If you have Docker installed, you can probably >>>> reproduce it >>>> locally. >>>> >>>> === TEST SCRIPT BEGIN === >>>> #!/bin/bash >>>> make docker-image-centos7 V=1 NETWORK=1 >>>> time make docker-test-quick@centos7 SHOW_ENV=1 J=14 NETWORK=1 >>>> === TEST SCRIPT END === >>>> >>>> TEST iotest-qcow2: 268 >>>> Failures: 141 >>> >>> Hm... 141 didn't fail in my test machine. I'm going to have a look. >> >> So here's the output: >> >> --- /root/qemu/tests/qemu-iotests/141.out 2019-11-12 04:43:27.651557587 >> -0500 >> +++ /root/qemu/build/tests/qemu-iotests/141.out.bad 2019-11-13 >> 08:12:06.575967337 -0500 >> @@ -10,6 +10,8 @@ >> Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 >> backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT >> {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": >> "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}} >> {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": >> "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}} >> +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": >> "JOB_STATUS_CHANGE", "data": {"status": "paused", "id": "job0"}} >> +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": >> "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}} >> {"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: node is >> used as backing hd of 'NODE_NAME'"}} >> {"return": {}} >> {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": >> "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "job0"}} >> >> Those extra lines, the "paused" and "running", are a result of the job >> being done in a transaction, within a drained section. >> >> We can update 141.out, but now I'm wondering, was it safe creating the >> job at do_drive_backup() outside of a drained section, as >> qmp_drive_backup was doing? > > I think it is. Someone needs to drain the source node before attaching > the job filter (which intercepts writes), and bdrv_backup_top_append() > does precisely this. > > If the source node is in an I/O thread, you could argue that the drain > starts later than when the user has invoked the backup command, and so > some writes might slip through. That’s correct. But at the same time, > it’s impossible to drain it the instant the command is received. So > some writes might always slip through (and the drain will not stop them > either, it will just let them happen). > > Therefore, I think it’s fine the way it is. > >> Do you think there may be any potential drawbacks as a result of always >> doing it now inside a drained section? > > Well, one drawback is clearly visible. The job goes to paused for no > reason.
This is something that already happens when requesting the drive-backup
through a transaction:
{"execute":"transaction","arguments":{"actions":[{"type":"drive-backup","data":{"device":"drv0","target":"o.qcow2","sync":"full","format":"qcow2"}}]}}
I don't think it makes sense to have two different behaviors for the
same action. So we either accept the additional pause+resume iteration
for qmp_drive_backup, or we remove the drained section from the
transaction based one.
What do you think?
Cheers,
Sergio.
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