06.06.2019 16:06, Kevin Wolf wrote: > Am 06.06.2019 um 14:29 hat Vladimir Sementsov-Ogievskiy geschrieben: >> 06.06.2019 13:05, Kevin Wolf wrote: >>> Am 05.06.2019 um 19:16 hat Vladimir Sementsov-Ogievskiy geschrieben: >>>> 05.06.2019 20:11, Kevin Wolf wrote: >>>>> Am 05.06.2019 um 14:32 hat Vladimir Sementsov-Ogievskiy geschrieben: >>>>>> child_role job already has .stay_at_node=true, so on bdrv_replace_node >>>>>> operation these child are unchanged. Make block job blk behave in same >>>>>> manner, to avoid inconsistent intermediate graph states and workarounds >>>>>> like in mirror. >>>>>> >>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> >>>>> >>>>> This feels dangerous. It does what you want it to do if the only graph >>>>> change below the BlockBackend is the one in mirror_exit_common. But the >>>>> user could also take a snapshot, or in the future hopefully insert a >>>>> filter node, and you would then want the BlockBackend to move. >>>>> >>>>> To be honest, even BdrvChildRole.stay_at_node is a bit of a hack. But at >>>>> least it's only used for permissions and not for the actual data flow. >>>> >>>> Hmm. Than, may be just add a parameter to bdrv_replace_node, which parents >>>> to ignore? Would it work? >>> >>> I would have to think a bit more about it, but it does sound safer. >>> >>> Or we take a step back and ask why it's even a problem for the mirror >>> block job if the BlockBackend is moved to a different node. The main >>> reason I see is because of bs->job that is set for the root node of the >>> BlockBackend and needs to be unset for the same node. >>> >>> Maybe we can just finally get rid of bs->job? It doesn't have many users >>> any more. >>> >> >> Hmm, looked at it. Not sure what should be refactored around job to get rid >> of "main node" concept.. Which seems to be in a bad relation with starting >> job on implicit filters as a main node.. >> >> But about just removing bs->job pointer, I don't know at least what to do >> with >> blk_iostatus_reset and blockdev_mark_auto_del.. > > blk_iostatus_reset() looks easy. It has only two callers: > > 1. blk_attach_dev(). This doesn't have anything to do with jobs and > attaching a new guest device won't solve any problem the job > encountered, so no reason to reset the iostatus for the job. > > 2. qmp_cont(). This resets the iostatus for everything. We can just > call block_job_iostatus_reset() for all block jobs instead of going > through BlockBackend. > > blockdev_mark_auto_del() might be a bit trickier. The whole idea of the > function is: When a guest device gets unplugged, automatically remove > its root block node, too. Commit 12bde0eed6b made it cancel a block job > because that should happen immediately when the device is actually > released by the guest and not only after the job finishes and gives up > its reference. I would like to just change the behaviour, but I'm afraid > we can't do this because of compatibility. > > However, just checking bs->job is really only one special case of > another user of the node to be deleted. Maybe we can extend it a little > so that any block jobs that contain the node in job->nodes are > cancelled. >
OK, thanks. I'll try this way -- Best regards, Vladimir
