It seems that bdrv_open_driver() forgot to create a coroutine where to call bs->drv->bdrv_co_drain_begin(), a callback marked as coroutine_fn.
Because there is no active I/O at this point, the coroutine should end right after entering, so the caller does not need to poll until it is finished. Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com> Reviewed-by: Paolo Bonzini <pbonz...@redhat.com> --- block.c | 36 +++++++++++++++++++++++++++++++----- 1 file changed, 31 insertions(+), 5 deletions(-) diff --git a/block.c b/block.c index 5311b21f8e..d2b2800039 100644 --- a/block.c +++ b/block.c @@ -1637,12 +1637,34 @@ out: g_free(gen_node_name); } +typedef struct DrainCo { + BlockDriverState *bs; + int ret; +} DrainCo; + +static void coroutine_fn bdrv_co_drain_begin(void *opaque) +{ + int i; + DrainCo *co = opaque; + BlockDriverState *bs = co->bs; + + for (i = 0; i < bs->quiesce_counter; i++) { + bs->drv->bdrv_co_drain_begin(bs); + } + co->ret = 0; +} + static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv, const char *node_name, QDict *options, int open_flags, Error **errp) { Error *local_err = NULL; - int i, ret; + int ret; + Coroutine *co; + DrainCo dco = { + .bs = bs, + .ret = NOT_DONE, + }; GLOBAL_STATE_CODE(); bdrv_assign_node_name(bs, node_name, &local_err); @@ -1690,10 +1712,14 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv, assert(bdrv_min_mem_align(bs) != 0); assert(is_power_of_2(bs->bl.request_alignment)); - for (i = 0; i < bs->quiesce_counter; i++) { - if (drv->bdrv_co_drain_begin) { - drv->bdrv_co_drain_begin(bs); - } + if (drv->bdrv_co_drain_begin) { + co = qemu_coroutine_create(bdrv_co_drain_begin, &dco); + qemu_coroutine_enter(co); + /* + * There should be no reason for drv->bdrv_co_drain_begin to wait at + * this point, because the device does not have any active I/O. + */ + assert(dco.ret != NOT_DONE); } return 0; -- 2.31.1