Re: [Qemu-devel] [PATCH v3] virtio-blk: Fix double completion for werror=stop

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Nov 17, 2015 at 06:20:11PM +0800, Fam Zheng wrote:
> When a request R is absorbed by request M, it is appended to the
> "mr_next" queue led by M, and is completed together with the completion
> of M, in virtio_blk_rw_complete.
> 
> During DMA restart in virtio_blk_dma_restart_bh, requests in s->rq are
> parsed and submitted again, possibly with a stale req->mr_next. It could
> be a problem if the request merging in virtio_blk_handle_request hasn't
> refreshed every mr_next pointer, in which case, virtio_blk_rw_complete
> could walk through unexpected requests following the stale pointers.
> 
> Fix this by unsetting the pointer in virtio_blk_rw_complete. It is safe
> because this req is either completed and freed right away, or it will be
> restarted and parsed from scratch out of the vq later.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> 
> v3: Fix as Stefan suggested.
> ---
>  hw/block/virtio-blk.c | 4 ++++
>  1 file changed, 4 insertions(+)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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