Am 08/11/2022 um 15:33 schrieb Vladimir Sementsov-Ogievskiy:
> On 11/4/22 12:56, Emanuele Giuseppe Esposito wrote:
>> 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.
>
> Hmm. I see your point. But isn't it better to go the generic way and use
> a generated coroutine wrapper? Nothing guarantees that
> .bdrv_co_drain_begin() handlers will never do any yield point even on
> driver open...
>
> Look for example at bdrv_co_check(). It has a generated wrapper
> bdrv_check(), declared in include/block/block-io.h
>
> So you just need to declare the wrapper, and use it in
> bdrv_open_driver(), the code would be clearer too.
I think (and this is a repetition from my previous email) it confuses
the code. It is clear, but then you don't know if we are in a coroutine
context or not.
I am very well aware of what you did with your script, and I am working
on extending your g_c_w class with g_c_w_simple, where we drop the
if(qemu_in_coroutine()) case and leave just the coroutine creation.
Therefore, coroutine functions we use only the _co_ function, otherwise
we use g_c_w_simple.
In this way code is clear as you point out, but there is no confusion.
Thank you,
Emanuele
>
>>
>> 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;
>
