Re: [Qemu-devel] [PATCH v11 01/19] block: Add bdrv_drain_all_{begin, end}()

[Alberto Garcia]

On Mon 24 Oct 2016 12:53:41 PM CEST, Paolo Bonzini wrote:

>> My first thoughts were about how to let an unpause succeed without a
>> previous pause for these objects, but actually I think this isn't
>> what we should do. We rather want to actually do the pause instead
>> because even new BDSes and block jobs should probably start in a
>> quiesced state when created inside a drain_all section.
>
> Yes, I agree with this.  It shouldn't be too hard to implement it.  It
> would require a BlockDriverState to look at the global "inside
> bdrv_drain_all_begin" state, and ask its BlockBackend to disable
> itself upon bdrv_replace_child.

Why in bdrv_replace_child()? bdrv_drain_all_end() enables all BDSs, but
if you add one with "blockdev-add" it's not going to be disabled using
this method.

In addition to that block jobs need the same, don't they? Something like
"job->pause_count = all_quiesce_counter" in the initialization.

I think we'd also need to add block_job_pause_point() at the beginning
of each one of their coroutines, in order to make sure that they really
start paused.

Berto