Re: [Qemu-devel] [PATCH v4 00/10] sheepdog: reconnect server after connection failure

[Stefan Hajnoczi]

On Fri, Jul 26, 2013 at 03:10:42PM +0900, MORITA Kazutaka wrote:
> Currently, if a sheepdog server exits, all the connecting VMs need to
> be restarted.  This series implements a feature to reconnect the
> server, and enables us to do online sheepdog upgrade and avoid
> restarting VMs when sheepdog servers crash unexpectedly.
> 
> v4:
>  - Added comment to explain why we need a failed queue.
>  - Fixed a return value of sd_acb_cancelable().
> 
> v3:
>  - Check return values of qemu_co_recv/send more strictly.
>  - Move inflight requests to the failed list after reconnection
>    completes.  This is necessary to resend I/Os while connection is
>    lost.
>  - Check simultaneous create in resend_aioreq().
> 
> v2:
>  - Dropped nonblocking connect patches.
> 
> MORITA Kazutaka (10):
>   ignore SIGPIPE in qemu-img and qemu-io
>   iov: handle EOF in iov_send_recv
>   sheepdog: check return values of qemu_co_recv/send correctly
>   sheepdog: handle vdi objects in resend_aio_req
>   sheepdog: reload inode outside of resend_aioreq
>   coroutine: add co_aio_sleep_ns() to allow sleep in block drivers
>   sheepdog: try to reconnect to sheepdog after network error
>   sheepdog: make add_aio_request and send_aioreq void functions
>   sheepdog: cancel aio requests if possible
>   sheepdog: check simultaneous create in resend_aioreq
> 
>  block/sheepdog.c          | 320 
> +++++++++++++++++++++++++++++-----------------
>  include/block/coroutine.h |   8 ++
>  qemu-coroutine-sleep.c    |  47 +++++++
>  qemu-img.c                |   4 +
>  qemu-io.c                 |   4 +
>  util/iov.c                |   6 +
>  6 files changed, 269 insertions(+), 120 deletions(-)

I have done a brief review.  The biggest change that I suggest using the
new AioContext timer support that Alex Bligh and Ping Fan are working on
(see qemu-devel for the latest patches).  It provides a way to use a
timer during qemu_aio_wait() without spinning.

CCed Nick Thomas who worked on NBD reconnect.  Maybe your series will
motivate him to push his patches again, or he might have some review
suggestions for you.