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block: add the support to drain throttled requests

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Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
[ Iterate until all block devices have processed all requests,
  add comments. - Paolo ]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Zhi Yong Wu 2012-04-12 14:00:57 +02:00 committed by Kevin Wolf
parent 1b3e76ebd1
commit 4c355d53c6
1 changed files with 20 additions and 1 deletions
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21
block.c
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@ -906,12 +906,31 @@ 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 can come until the
* coroutine is complete. Because of this, it is not possible to have a
* function 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.
*/
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) {