On Tue, Mar 13, 2012 at 2:22 AM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> From: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
>
> Signed-off-by: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
> [ Iterate until all block devices have processed all requests,
> add comments. - Paolo ]
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block.c | 21 ++++++++++++++++++++-
> 1 files changed, 20 insertions(+), 1 deletions(-)
>
> diff --git a/block.c b/block.c
> index dac62a1..0d769a6 100644
> --- a/block.c
> +++ b/block.c
> @@ -858,12 +858,31 @@ void bdrv_close_all(void)
> *
> * This function does not flush data to disk, use bdrv_flush_all() for that
> * after calling this function.
> + *
> + * Note that completion of an asynchronous I/O operation can trigger any
> + * number of other I/O operations on other devices---for example a coroutine
> + * can be arbitrarily complex and a constant flow of I/O to multiple devices
> + * can come until the coroutine is complete. Because of this, it is not
> + * possible to drain a single device's I/O queue.
> */
> void bdrv_drain_all(void)
> {
> BlockDriverState *bs;
> + bool busy;
>
> - qemu_aio_flush();
> + do {
> + busy = qemu_aio_wait();
> +
> + /* FIXME: We do not have timer support here, so this is effectively
> + * a busy wait.
Maybe we can temporarily disable I/O throttling, after flush is
completed, enable it again. But this perhaps affects other guest.
> + */
> + QTAILQ_FOREACH(bs, &bdrv_states, list) {
> + if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
> + qemu_co_queue_restart_all(&bs->throttled_reqs);
> + busy = true;
> + }
> + }
> + } while (busy);
>
> /* If requests are still pending there is a bug somewhere */
> QTAILQ_FOREACH(bs, &bdrv_states, list) {
> --
> 1.7.7.6
>
>
--
Regards,
Zhi Yong Wu
