On Tue 25 Oct 2016 04:38:27 PM CEST, Kevin Wolf 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.
>>
>> You only need to disable it when blk_insert_bs is called. In fact...
>
> This assumes that the block driver doesn't issue internal background I/O
> by itself. Probably true for everything that we have today, but it would
> probably be cleaner to quiesce it directly in bdrv_open_common().
And how about the rest of the things that are going on in
bdrv_drain_all_begin()?
bdrv_parent_drained_begin(bs);
bdrv_io_unplugged_begin(bs);
bdrv_drain_recurse(bs);
aio_disable_external(aio_context);
Berto
