block: fix null-pointer bug on error case in block commit

This is a bug that was caught by a coverity run by Markus.  In
the error case when we errored out to exit_restore_open early in the
function, 'overlay_bs' was still NULL at that point, although it is
used to look up flags and perform a bdrv_reopen().

Move the overlay_bs lookup to where it is needed, and check for NULL
before restoring the flags.  Also get rid of the unneeded parameter
initialization.

Reported-By: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
ide: Remove wrong assertion

The Bus Master IDE Active bit (BM_STATUS_DMAING) is not only set when
the request is still in flight, but also when it has completed and the
size of the physical memory regions in the PRDT was larger than the
transfer size.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
aio: Fix return value of aio_poll()

aio_poll() must return true if any work is still pending, even if it
didn't make progress, so that bdrv_drain_all() doesn't stop waiting too
early. The possibility of stopping early occasionally lead to a failed
assertion in bdrv_drain_all(), when some in-flight request was missed
and the function didn't really drain all requests.

In order to make that change, the return value as specified in the
function comment must change for blocking = false; fortunately, the
return value of blocking = false callers is only used in test cases, so
this change shouldn't cause any trouble.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
win32-aio: Fix vectored reads

Copying data in the right direction really helps a lot!

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
win32-aio: Fix memory leak

The buffer is allocated for both reads and writes, and obviously it
should be freed even if an error occurs.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
win32-aio: use iov utility functions instead of open-coding them

We have iov_from_buf() and iov_to_buf(), use them instead of
open-coding these in block/win32-aio.c

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
dataplane: avoid reentrancy during virtio_blk_data_plane_stop()

When dataplane is stopping, the s->vdev->binding->set_host_notifier(...,
false) call can invoke the virtqueue handler if an ioeventfd
notification is pending.  This causes hw/virtio-blk.c to invoke
virtio_blk_data_plane_start() before virtio_blk_data_plane_stop()
returns!

The result is that we try to restart dataplane while trying to stop it
and the following assertion is raised:

  msix_set_mask_notifier: Assertion `!dev->msix_mask_notifier' failed.

Although the code was intended to prevent this scenario, the s->started
boolean isn't enough.  Add s->stopping so that we can postpone clearing
s->started until we've completely stopped dataplane.

This way, virtqueue handler calls during virtio_blk_data_plane_stop()
are ignored.  When dataplane is legitimately started again later we
already self-kick ourselves to resume processing.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
dataplane: support viostor virtio-pci status bit setting

The viostor virtio-blk driver for Windows does not use the
VIRTIO_CONFIG_S_DRIVER bit.  It only sets the VIRTIO_CONFIG_S_DRIVER_OK
bit.

The viostor driver refreshes the virtio-pci status byte sometimes while
the guest is running.  We misinterpret 0x4 (VIRTIO_CONFIG_S_DRIVER_OK)
as an indication that virtio-blk-data-plane should be stopped since 0x2
(VIRTIO_CONFIG_S_DRIVER) is missing.  The result is that the device
becomes unresponsive.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Merge remote-tracking branch 'stefanha/block' into staging

# By Kevin Wolf (4) and others
# Via Stefan Hajnoczi
* stefanha/block:
  dataplane: support viostor virtio-pci status bit setting
  dataplane: avoid reentrancy during virtio_blk_data_plane_stop()
  win32-aio: use iov utility functions instead of open-coding them
  win32-aio: Fix memory leak
  win32-aio: Fix vectored reads
  aio: Fix return value of aio_poll()
  ide: Remove wrong assertion
  block: fix null-pointer bug on error case in block commit