Re: [Qemu-devel] [PATCH 1/3] blockdev-backup: Don't move target AioContext if it's attached

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, May 18, 2016 at 04:24:08PM +0800, Fam Zheng wrote:
> If the BDS is attached, it will want to stay on the AioContext where its
> BlockBackend is. Don't call bdrv_set_aio_context in this case.

What should the user do when they hit this error?

> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  blockdev.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 1892b8e..eb15593 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -3376,8 +3376,18 @@ void do_blockdev_backup(const char *device, const char *target,
>      }
>      target_bs = blk_bs(target_blk);
>  
> +    if (bdrv_get_aio_context(target_bs) != aio_context) {
> +        if (!target_bs->blk) {
> +            /* The target BDS is not attached, we can safely move it to another
> +             * AioContext. */
> +            bdrv_set_aio_context(target_bs, aio_context);
> +        } else {
> +            error_setg(errp, "Target is attached to a different thread from "
> +                             "source.");
> +            goto out;
> +        }
> +    }
>      bdrv_ref(target_bs);
> -    bdrv_set_aio_context(target_bs, aio_context);
>      backup_start(bs, target_bs, speed, sync, NULL, on_source_error,
>                   on_target_error, block_job_cb, bs, txn, &local_err);
>      if (local_err != NULL) {
> -- 
> 2.8.2
> 

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