Re: [Qemu-devel] [PATCH v2 5/7] block/nbd-client: nbd_co_send_request: return -EIO if s->quit was set in parallel

[Eric Blake]

On 09/18/2017 08:59 AM, Vladimir Sementsov-Ogievskiy wrote:
> It's incorrect to return success rc >= 0 if we skip qio_channel_writev_all()
> call due to s->quit.

Does this need to cc: qemu-stable for 2.10.1 (or put another way, can we
come up with some scenario of EAGAIN or other handling that would
actually set s->quit in a parallel coroutine when a client sends out
multiple requests at once)?

> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  block/nbd-client.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index f331f08a9a..280147e6a7 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -189,6 +189,9 @@ static int nbd_co_send_request(BlockDriverState *bs,
>      }
>  
>  err:
> +    if (rc >= 0 && s->quit) {
> +        rc = -EIO;
> +    }

I'm still not convinced this is in the right place.  This fails the
send_request regardless of whether we skipped qio_channel_writev_all();
shouldn't the rc be set only in the case that we actually skipped
writing the full command because s->quit was detected at that point in time?

>      if (rc < 0) {
>          s->quit = true;
>          s->requests[i].coroutine = NULL;
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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