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