Re: [Qemu-devel] [PATCH 2/3] virtio-blk: Use blk_drain() to drain IO requests

[Fam Zheng <famz@redhat.com>]

On Wed, 06/10 14:38, Alexander Yarygin wrote:
> Each call of the virtio_blk_reset() function calls blk_drain_all(),
> which works for all existing BlockDriverStates, while draining only
> one is needed.
> 
> This patch replaces blk_drain_all() by blk_drain() in virtio_blk_reset().

Please add a note "virtio_blk_data_plane_stop should be called after draining
because it restores vblk->complete_request" as well.
> 
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>

Cc: qemu-stable@nongnu.org

> Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
> ---
>  hw/block/virtio-blk.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index e6afe97..2009092 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -652,15 +652,16 @@ static void virtio_blk_reset(VirtIODevice *vdev)
>  {
>      VirtIOBlock *s = VIRTIO_BLK(vdev);
>  
> -    if (s->dataplane) {
> -        virtio_blk_data_plane_stop(s->dataplane);
> -    }
> -
>      /*
>       * This should cancel pending requests, but can't do nicely until there
>       * are per-device request lists.
>       */

This comment can be dropped now.

> -    blk_drain_all();
> +    blk_drain(s->blk);
> +
> +    if (s->dataplane) {
> +        virtio_blk_data_plane_stop(s->dataplane);
> +    }
> +
>      blk_set_enable_write_cache(s->blk, s->original_wce);
>  }
>  
> -- 
> 1.9.1
> 
>