[sheepdog] [PATCH] sheep: fix null reference bug

[Christoph Hellwig]

On Tue, May 29, 2012 at 03:47:40PM +0800, Liu Yuan wrote:
> From: Liu Yuan <tailai.ly at taobao.com>
> 
> Fix the following segfault:
> 
> So the fix is to provide a check before calling list_del in io_op_done().

The fix is to stop abusing the ->done callback in check_request, as pointed
out in my reviews to the recovery series.  I'll send it as part of my next series.