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block: Add bdrv_aio_cancel_async

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This is the async version of bdrv_aio_cancel, which doesn't block the
caller. It guarantees that the cb is called either before returning or
some time later.

bdrv_aio_cancel can base on bdrv_aio_cancel_async, later we can convert
all .io_cancel implementations to .io_cancel_async, and the aio_poll is
the common logic. In the end, .io_cancel can be dropped.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Fam Zheng 2014-09-11 13:41:09 +08:00 • committed by Stefan Hajnoczi
parent f197fe2b2c
commit 02c50efe08
3 changed files with 29 additions and 1 deletions
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27
block.c
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@ -4640,7 +4640,32 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs)
void bdrv_aio_cancel(BlockDriverAIOCB *acb)
{
acb->aiocb_info->cancel(acb);
if (acb->aiocb_info->cancel) {
acb->aiocb_info->cancel(acb);
} else {
qemu_aio_ref(acb);
bdrv_aio_cancel_async(acb);
while (acb->refcnt > 1) {
if (acb->aiocb_info->get_aio_context) {
aio_poll(acb->aiocb_info->get_aio_context(acb), true);
} else if (acb->bs) {
aio_poll(bdrv_get_aio_context(acb->bs), true);
} else {
abort();
}
}
qemu_aio_release(acb);
}
}
/* Async version of aio cancel. The caller is not blocked if the acb implements
* cancel_async, otherwise we do nothing and let the request normally complete.
* In either case the completion callback must be called. */
void bdrv_aio_cancel_async(BlockDriverAIOCB *acb)
{
if (acb->aiocb_info->cancel_async) {
acb->aiocb_info->cancel_async(acb);
}
}
/**************************************************************/