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Date: Wed, 06 May 2015 14:07:39 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH 6/7] virtio-blk: Don't handle output
 when there is "device IO" op blocker
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To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, jcody@redhat.com, armbru@redhat.com, mreitz@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>



On 06/05/2015 13:23, Fam Zheng wrote:
> virtio-blk now listens to op blocker change of the associated block
> backend.
> 
> Up on setting op blocker on BLOCK_OP_TYPE_DEVICE_IO:
> 
>   non-dataplane:
>    1) Set VirtIOBlock.paused
>    2) In virtio_blk_handle_output, do nothing if VirtIOBlock.paused
> 
>   dataplane:
>    1) Clear the host event notifier
>    2) In handle_notify, do nothing if VirtIOBlock.paused
> 
> Up on removing the op blocker:
> 
>   non-dataplane:
>    1) Clear VirtIOBlock.paused
>    2) Schedule a BH on the AioContext of the backend, which calls
>    virtio_blk_handle_output, so that the previous unhandled kicks can
>    make progress
> 
>   dataplane:
>    1) Set the host event notifier
>    2) Notify the host event notifier so that unhandled events are
>    processed
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>

Does non-dataplane need to do anything, since it uses iohandlers rather
than aio_set_event_notifier_handler?

Paolo