Re: [Qemu-devel] [PATCH for-2.9] block: get rid of bdrv_io_unplugged_begin/end

[Paolo Bonzini]

On 29/11/2016 12:33, Paolo Bonzini wrote:
> bdrv_io_plug and bdrv_io_unplug are only called (via their
> BlockBackend equivalents) after starting asynchronous I/O.
> bdrv_drain is not going to be called while they are running,
> because---even if a coroutine runs for some reason---it will
> only drain in the next iteration of the event loop through
> bdrv_co_yield_to_drain.
> 
> So this mechanism is unnecessary, get rid of it.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  block/io.c                | 41 ++---------------------------------------
>  include/block/block.h     |  2 --
>  include/block/block_int.h |  3 +--
>  3 files changed, 3 insertions(+), 43 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 4f00562..c42b34a 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -228,9 +228,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
>          bdrv_parent_drained_begin(bs);
>      }
>  
> -    bdrv_io_unplugged_begin(bs);
>      bdrv_drain_recurse(bs);
> -    bdrv_io_unplugged_end(bs);
>  }
>  
>  void bdrv_drained_end(BlockDriverState *bs)
> @@ -302,7 +300,6 @@ void bdrv_drain_all_begin(void)
>  
>          aio_context_acquire(aio_context);
>          bdrv_parent_drained_begin(bs);
> -        bdrv_io_unplugged_begin(bs);
>          aio_disable_external(aio_context);
>          aio_context_release(aio_context);
>  
> @@ -347,7 +344,6 @@ void bdrv_drain_all_end(void)
>  
>          aio_context_acquire(aio_context);
>          aio_enable_external(aio_context);
> -        bdrv_io_unplugged_end(bs);
>          bdrv_parent_drained_end(bs);
>          aio_context_release(aio_context);
>      }
> @@ -2650,7 +2646,7 @@ void bdrv_io_plug(BlockDriverState *bs)
>          bdrv_io_plug(child->bs);
>      }
>  
> -    if (bs->io_plugged++ == 0 && bs->io_plug_disabled == 0) {
> +    if (bs->io_plugged++ == 0) {
>          BlockDriver *drv = bs->drv;
>          if (drv && drv->bdrv_io_plug) {
>              drv->bdrv_io_plug(bs);
> @@ -2663,7 +2659,7 @@ void bdrv_io_unplug(BlockDriverState *bs)
>      BdrvChild *child;
>  
>      assert(bs->io_plugged);
> -    if (--bs->io_plugged == 0 && bs->io_plug_disabled == 0) {
> +    if (--bs->io_plugged == 0) {
>          BlockDriver *drv = bs->drv;
>          if (drv && drv->bdrv_io_unplug) {
>              drv->bdrv_io_unplug(bs);
> @@ -2674,36 +2670,3 @@ void bdrv_io_unplug(BlockDriverState *bs)
>          bdrv_io_unplug(child->bs);
>      }
>  }
> -
> -void bdrv_io_unplugged_begin(BlockDriverState *bs)
> -{
> -    BdrvChild *child;
> -
> -    if (bs->io_plug_disabled++ == 0 && bs->io_plugged > 0) {
> -        BlockDriver *drv = bs->drv;
> -        if (drv && drv->bdrv_io_unplug) {
> -            drv->bdrv_io_unplug(bs);
> -        }
> -    }
> -
> -    QLIST_FOREACH(child, &bs->children, next) {
> -        bdrv_io_unplugged_begin(child->bs);
> -    }
> -}
> -
> -void bdrv_io_unplugged_end(BlockDriverState *bs)
> -{
> -    BdrvChild *child;
> -
> -    assert(bs->io_plug_disabled);
> -    QLIST_FOREACH(child, &bs->children, next) {
> -        bdrv_io_unplugged_end(child->bs);
> -    }
> -
> -    if (--bs->io_plug_disabled == 0 && bs->io_plugged > 0) {
> -        BlockDriver *drv = bs->drv;
> -        if (drv && drv->bdrv_io_plug) {
> -            drv->bdrv_io_plug(bs);
> -        }
> -    }
> -}
> diff --git a/include/block/block.h b/include/block/block.h
> index 49bb0b2..8b0dcda 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -526,8 +526,6 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry 
> *geo);
>  
>  void bdrv_io_plug(BlockDriverState *bs);
>  void bdrv_io_unplug(BlockDriverState *bs);
> -void bdrv_io_unplugged_begin(BlockDriverState *bs);
> -void bdrv_io_unplugged_end(BlockDriverState *bs);
>  
>  /**
>   * bdrv_drained_begin:
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 83a423c..15aa718 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -526,9 +526,8 @@ struct BlockDriverState {
>      uint64_t write_threshold_offset;
>      NotifierWithReturn write_threshold_notifier;
>  
> -    /* counters for nested bdrv_io_plug and bdrv_io_unplugged_begin */
> +    /* counter for nested bdrv_io_plug */
>      unsigned io_plugged;
> -    unsigned io_plug_disabled;
>  
>      int quiesce_counter;
>  };
> 

Ping?

Paolo