Stop using a custom Linux AIO request queue from ioq.h and instead use
the QEMU block layer for I/O.
This patch adjusts the VirtIOBlockRequest struct with fields needed for
bdrv_aio_readv()/bdrv_aio_writev(). ioq.h used struct iovec and struct
iocb, which we don't need directly anymore.
Modify dataplane start/stop to set the AioContext on the
BlockDriverState. We also no longer need to get the raw-posix file
descriptor. This means image formats are now supported with dataplane!
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
580b6b2aa2