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. Kevin
