On 21.10.2015 13:49, Alberto Garcia wrote: > On Mon 19 Oct 2015 05:53:37 PM CEST, Max Reitz wrote: >> And a helper function for that, which directly takes a pointer to the >> BDS to be inserted instead of its node-name (which will be used for >> implementing 'change' using blockdev-insert-medium). > > Shouldn't this update bdrv_states?
I hate bdrv_states.
Yes, it should. Thanks!
Max
> Consider this scenario:
>
> 1) We add a drive and eject its BDS
> { "execute": "blockdev-add", "arguments": {
> "options": { "driver": "qcow2",
> "file": { "driver": "file",
> "filename": "/tmp/hd0.img"},
> "id": "drive0" }}}
>
> { "execute": "eject", "arguments": {"device": "drive0"}}
>
> 2) We create a new BDS and insert it in drive0
> { "execute": "blockdev-add", "arguments": {
> "options": { "driver": "qcow2",
> "file": { "driver": "file",
> "filename": "/tmp/hd0.img"},
> "node-name": "hd0" }}}
>
> { "execute": "blockdev-insert-medium", "arguments": {
> "device": "drive0",
> "node-name": "hd0" }}
>
> 3) Now we try to create a snapshot...
>
> { "execute": "blockdev-snapshot-sync", "arguments": {
> "device": "drive0",
> "snapshot-file": "/tmp/new.img",
> "format": "qcow2" }}
>
> {"error": {"class": "GenericError",
> "desc": "The feature 'snapshot' is not enabled"}}
>
> Ooops! It seems that this is because the new node hd0 is not in the
> bdrv_states list.
>
> 4) Let's try to create a mirror instead
>
> { "execute": "drive-mirror", "arguments": {
> "device": "drive0",
> "target": "/tmp/new.img",
> "sync": "top"}}
>
> {"return": {}}
> {"timestamp": {"seconds": 1445427560,
> "microseconds": 765993},
> "event": "BLOCK_JOB_READY",
> "data": {"device": "drive0",
> "len": 0,
> "offset": 0,
> "speed": 0,
> "type": "mirror"}}
>
> 5) Ok, the block job is ready, so let's complete it:
>
> { "execute": "query-block-jobs" }
> {"return": []}
>
> Ooops! Again, hd0 is not in bdrv_states so QEMU cannot find the block
> job.
>
> 6) Anyway, we only need the backend name in order to complete a block
> job, so surely we can do it even if it's not in the list:
>
> { "execute": "block-job-complete", "arguments": {
> "device": "drive0"}}
>
> Segmentation fault
>
> That's QTAILQ_INSERT_BEFORE() in change_parent_backing_link(). This
> code assumes that since the 'from' BDS is attached to a backend, it
> must also be in bdrv_states.
>
> Berto
>
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