Commit 0109e7e6 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Defer .bdrv_drain_begin callback to polling phase 



We cannot allow aio_poll() in bdrv_drain_invoke(begin=true) until we're
done with propagating the drain through the graph and are doing the
single final BDRV_POLL_WHILE().

Just schedule the coroutine with the callback and increase bs->in_flight
to make sure that the polling phase will wait for it.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 231281ab

block/io.c

+23 −5
Original line number Diff line number Diff line
@@ -182,22 +182,40 @@ static void coroutine_fn bdrv_drain_invoke_entry(void *opaque) 


    /* Set data->done before reading bs->wakeup.  */

    atomic_mb_set(&data->done, true);

    bdrv_wakeup(bs);

    bdrv_dec_in_flight(bs);



    if (data->begin) {

        g_free(data);

    }

}



/* Recursively call BlockDriver.bdrv_co_drain_begin/end callbacks */

static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)

{

    BdrvCoDrainData data = { .bs = bs, .done = false, .begin = begin};

    BdrvCoDrainData *data;



    if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) ||

            (!begin && !bs->drv->bdrv_co_drain_end)) {

        return;

    }



    data.co = qemu_coroutine_create(bdrv_drain_invoke_entry, &data);

    bdrv_coroutine_enter(bs, data.co);

    BDRV_POLL_WHILE(bs, !data.done);

    data = g_new(BdrvCoDrainData, 1);

    *data = (BdrvCoDrainData) {

        .bs = bs,

        .done = false,

        .begin = begin

    };



    /* Make sure the driver callback completes during the polling phase for

     * drain_begin. */

    bdrv_inc_in_flight(bs);

    data->co = qemu_coroutine_create(bdrv_drain_invoke_entry, data);

    aio_co_schedule(bdrv_get_aio_context(bs), data->co);



    if (!begin) {

        BDRV_POLL_WHILE(bs, !data->done);

        g_free(data);

    }

}



/* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */