Re: [Qemu-devel] [PATCH for-2.9?] 9pfs: fix multiple flush for same request

[Eric Blake]

On 03/30/2017 03:26 AM, Greg Kurz wrote:
> If a client tries to flush the same outstanding request several times, only
> the first flush completes. Subsequent ones keep waiting for the request
> completion in v9fs_flush() and, therefore, leak a PDU. This will cause QEMU
> to hang when draining active PDUs the next time the device is reset.

Since this fixes a hang, is it 2.9 material?

> 
> Let have each flush request wake up the next one if any. The last waiter
> frees the cancelled PDU.
> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/9pfs/9p.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 

Reviewed-by: Eric Blake <address@hidden>

> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index 48babce836b6..ef47a0a5ad6f 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -2387,8 +2387,10 @@ static void coroutine_fn v9fs_flush(void *opaque)
>           * Wait for pdu to complete.
>           */
>          qemu_co_queue_wait(&cancel_pdu->complete, NULL);
> -        cancel_pdu->cancelled = 0;
> -        pdu_free(cancel_pdu);
> +        if (!qemu_co_queue_next(&cancel_pdu->complete)) {
> +            cancel_pdu->cancelled = 0;
> +            pdu_free(cancel_pdu);
> +        }
>      }
>      pdu_complete(pdu, 7);
>  }
> 
> 
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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