Re: [Qemu-devel] [PATCH 1/2] block-backend: Introduce blk_drain() and replace blk_drain_all()

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am 03.06.2015 um 15:46 schrieb Alexander Yarygin:
> Each call of the virtio_blk_reset() function calls blk_drain_all(),
> which works for all existing BlockDriverStates, while only one
> BlockDriverState needs to be drained.
> 
> This patch introduces the blk_drain() function and replaces
> blk_drain_all() on it in virtio_blk_reset().

> 
> 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>
> Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>

Seems to solve the main issue and causes no visible regression on a quick shot
with my testcase.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>

> ---
>  block/block-backend.c          | 5 +++++
>  hw/block/virtio-blk.c          | 2 +-
>  include/sysemu/block-backend.h | 1 +
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 93e46f3..aee8a12 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -700,6 +700,11 @@ int blk_flush_all(void)
>      return bdrv_flush_all();
>  }
> 
> +void blk_drain(BlockBackend *blk)
> +{
> +    bdrv_drain(blk->bs);
> +}
> +
>  void blk_drain_all(void)
>  {
>      bdrv_drain_all();
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index e6afe97..abaca58 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -660,7 +660,7 @@ static void virtio_blk_reset(VirtIODevice *vdev)
>       * This should cancel pending requests, but can't do nicely until there
>       * are per-device request lists.
>       */
> -    blk_drain_all();
> +    blk_drain(s->blk);
>      blk_set_enable_write_cache(s->blk, s->original_wce);
>  }
> 
> diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
> index b4a4d5e..8fc960f 100644
> --- a/include/sysemu/block-backend.h
> +++ b/include/sysemu/block-backend.h
> @@ -118,6 +118,7 @@ int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors);
>  int blk_co_flush(BlockBackend *blk);
>  int blk_flush(BlockBackend *blk);
>  int blk_flush_all(void);
> +void blk_drain(BlockBackend *blk);
>  void blk_drain_all(void);
>  BlockdevOnError blk_get_on_error(BlockBackend *blk, bool is_read);
>  BlockErrorAction blk_get_error_action(BlockBackend *blk, bool is_read,
>