| Message ID | 1458123018-18651-2-git-send-email-famz@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 16/03/2016 11:10, Fam Zheng wrote: > An empty begin/end pair is almost the same as a bare bdrv_drain except > the aio_poll inside is wrapped by > aio_disable_external/aio_enable_external. > > This is safer, and is the only way to achieve quiescence in this > aio_poll(), because bdrv_drained_begin/end pair cannot span across > context detach/attach options, so it's not possible to do by the caller. I'm still not sure about this patch. When starting dataplane, the ioeventfd is registered with iohandler.c so bdrv_drained_begin/end is not necessary. Likewise when stopping dataplane bdrv_set_aio_context is called after the thread has been stopped and thus the ioeventfd is not registered anymore as an external client. Paolo
On Wed, 03/16 11:27, Paolo Bonzini wrote: > > > On 16/03/2016 11:10, Fam Zheng wrote: > > An empty begin/end pair is almost the same as a bare bdrv_drain except > > the aio_poll inside is wrapped by > > aio_disable_external/aio_enable_external. > > > > This is safer, and is the only way to achieve quiescence in this > > aio_poll(), because bdrv_drained_begin/end pair cannot span across > > context detach/attach options, so it's not possible to do by the caller. > > I'm still not sure about this patch. > > When starting dataplane, the ioeventfd is registered with iohandler.c so > bdrv_drained_begin/end is not necessary. You are right, and looks like the k->set_host_notifier() above blk_set_aio_context would disable the fd anyway. > > Likewise when stopping dataplane bdrv_set_aio_context is called after > the thread has been stopped and thus the ioeventfd is not registered > anymore as an external client. Right. Fam
diff --git a/block.c b/block.c index 59a18a3..31f4a9f 100644 --- a/block.c +++ b/block.c @@ -3747,7 +3747,9 @@ void bdrv_attach_aio_context(BlockDriverState *bs, void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context) { - bdrv_drain(bs); /* ensure there are no in-flight requests */ + /* ensure there are no in-flight requests */ + bdrv_drained_begin(bs); + bdrv_drained_end(bs); bdrv_detach_aio_context(bs);
An empty begin/end pair is almost the same as a bare bdrv_drain except the aio_poll inside is wrapped by aio_disable_external/aio_enable_external. This is safer, and is the only way to achieve quiescence in this aio_poll(), because bdrv_drained_begin/end pair cannot span across context detach/attach options, so it's not possible to do by the caller. Signed-off-by: Fam Zheng <famz@redhat.com> --- block.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)