Re: [Qemu-devel] [PATCH v6 06/13] virtio-scsi-dataplane: Add "device IO" op blocker listener

[Max Reitz <mreitz@redhat.com>]

On 21.05.2015 08:42, Fam Zheng wrote:
> When a disk is attached to scsi-bus, virtio_scsi_hotplug will take care
> of protecting the block device with op blockers. Currently we haven't
> enabled block jobs (like what's done in virtio_blk_data_plane_create),
> but it is necessary to honor "device IO" op blocker first before we do.
> This is useful to make sure that guest IO requests are paused during qmp
> transactions (such as multi-disk snapshot or backup).
>
> A counter is added to the virtio-scsi device, which keeps track of
> currently blocked disks. If it goes from 0 to 1, the ioeventfds are
> disabled; when it goes back to 0, they are re-enabled.
>
> Also in device initialization, push the enabling of ioeventfds to before
> return, so the virtio_scsi_clear_aio is not needed there. Rename it,
> pair with an enabling variant, fix one coding style issue, then use it
> in the device pause points.
>
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>   hw/scsi/virtio-scsi-dataplane.c | 82 +++++++++++++++++++++++++++++++----------
>   hw/scsi/virtio-scsi.c           |  3 ++
>   include/hw/virtio/virtio-scsi.h |  3 ++
>   3 files changed, 68 insertions(+), 20 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>