Re: [Qemu-devel] [PATCH 2/3] virtio-blk: Remove op blocker for dataplane

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, May 18, 2016 at 04:24:09PM +0800, Fam Zheng wrote:
> Block layer is prepared to unspecialize dataplane, an evidence is this
> almost complete list of unblocked operations. It has all types except
> two (actually three if DATAPLANE itself counts but blockdev.c makes sure
> attaching twice is not possible): MIRROR_TARGET and BACKUP_TARGET.
> 
> blockdev-mirror refuses to start if target is attached, so the first is
> not a problem.
> 
> By removing BACKUP_TARGET, blockdev-backup will become permissive to
> write to a virtio-blk dataplane disk, but that is not worse than
> non-dataplane given the latter is already possible. In either case,
> blockdev.c always checks the target and source are on the same
> AioContext, or bring them together if possible.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/block/dataplane/virtio-blk.c | 63 -----------------------------------------
>  1 file changed, 63 deletions(-)
> 
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 3cb97c9..2073f9a 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -37,8 +37,6 @@ struct VirtIOBlockDataPlane {
>      EventNotifier *guest_notifier;  /* irq */
>      QEMUBH *bh;                     /* bh for guest notification */
>  
> -    Notifier insert_notifier, remove_notifier;
> -
>      /* Note that these EventNotifiers are assigned by value.  This is
>       * fine as long as you do not call event_notifier_cleanup on them
>       * (because you don't own the file descriptor or handle; you just
> @@ -46,9 +44,6 @@ struct VirtIOBlockDataPlane {
>       */
>      IOThread *iothread;
>      AioContext *ctx;
> -
> -    /* Operation blocker on BDS */
> -    Error *blocker;
>  };
>  
>  /* Raise an interrupt to signal guest, if necessary */
> @@ -68,54 +63,6 @@ static void notify_guest_bh(void *opaque)
>      event_notifier_set(s->guest_notifier);
>  }
>  
> -static void data_plane_set_up_op_blockers(VirtIOBlockDataPlane *s)
> -{
> -    assert(!s->blocker);
> -    error_setg(&s->blocker, "block device is in use by data plane");
> -    blk_op_block_all(s->conf->conf.blk, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_RESIZE, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_DRIVE_DEL, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_BACKUP_SOURCE, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_CHANGE, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_COMMIT_SOURCE, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_COMMIT_TARGET, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_EJECT, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT,
> -                   s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_INTERNAL_SNAPSHOT,
> -                   s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_INTERNAL_SNAPSHOT_DELETE,
> -                   s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_MIRROR_SOURCE, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_STREAM, s->blocker);
> -    blk_op_unblock(s->conf->conf.blk, BLOCK_OP_TYPE_REPLACE, s->blocker);
> -}
> -
> -static void data_plane_remove_op_blockers(VirtIOBlockDataPlane *s)
> -{
> -    if (s->blocker) {
> -        blk_op_unblock_all(s->conf->conf.blk, s->blocker);
> -        error_free(s->blocker);
> -        s->blocker = NULL;
> -    }
> -}
> -
> -static void data_plane_blk_insert_notifier(Notifier *n, void *data)
> -{
> -    VirtIOBlockDataPlane *s = container_of(n, VirtIOBlockDataPlane,
> -                                           insert_notifier);
> -    assert(s->conf->conf.blk == data);
> -    data_plane_set_up_op_blockers(s);
> -}
> -
> -static void data_plane_blk_remove_notifier(Notifier *n, void *data)
> -{
> -    VirtIOBlockDataPlane *s = container_of(n, VirtIOBlockDataPlane,
> -                                           remove_notifier);
> -    assert(s->conf->conf.blk == data);
> -    data_plane_remove_op_blockers(s);
> -}
> -
>  /* Context: QEMU global mutex held */
>  void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
>                                    VirtIOBlockDataPlane **dataplane,
> @@ -158,13 +105,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
>      s->ctx = iothread_get_aio_context(s->iothread);
>      s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
>  
> -    s->insert_notifier.notify = data_plane_blk_insert_notifier;
> -    s->remove_notifier.notify = data_plane_blk_remove_notifier;
> -    blk_add_insert_bs_notifier(conf->conf.blk, &s->insert_notifier);
> -    blk_add_remove_bs_notifier(conf->conf.blk, &s->remove_notifier);
> -
> -    data_plane_set_up_op_blockers(s);
> -
>      *dataplane = s;
>  }
>  
> @@ -176,9 +116,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
>      }
>  
>      virtio_blk_data_plane_stop(s);
> -    data_plane_remove_op_blockers(s);
> -    notifier_remove(&s->insert_notifier);
> -    notifier_remove(&s->remove_notifier);
>      qemu_bh_delete(s->bh);
>      object_unref(OBJECT(s->iothread));
>      g_free(s);
> -- 
> 2.8.2