Re: [Qemu-devel] [PATCH] sheepdog: set io_flush handler in do_co_req

[Stefan Hajnoczi <stefanha@redhat.com>]

On Mon, Mar 11, 2013 at 06:01:02PM +0900, MORITA Kazutaka wrote:
> If an io_flush handler is not set, qemu_aio_wait doesn't invoke
> callbacks.
> 
> Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
> ---
>  block/sheepdog.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index e4ec32d..cb0eeed 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -501,6 +501,13 @@ static void restart_co_req(void *opaque)
>      qemu_coroutine_enter(co, NULL);
>  }
>  
> +static int have_co_req(void *opaque)
> +{
> +    /* this handler is set only when there is a pending request, so
> +     * always returns 1. */
> +    return 1;
> +}
> +
>  typedef struct SheepdogReqCo {
>      int sockfd;
>      SheepdogReq *hdr;
> @@ -523,14 +530,14 @@ static coroutine_fn void do_co_req(void *opaque)
>      unsigned int *rlen = srco->rlen;
>  
>      co = qemu_coroutine_self();
> -    qemu_aio_set_fd_handler(sockfd, NULL, restart_co_req, NULL, co);
> +    qemu_aio_set_fd_handler(sockfd, NULL, restart_co_req, have_co_req, co);
>  
>      ret = send_co_req(sockfd, hdr, data, wlen);

Which tree is this patch against?  block/sheepdog.c:do_co_req() has a
socket_set_block(sockfd) call before this line.

Is there a guarantee that only one coroutine executes do_co_req() at a
time?  Otherwise the first coroutine that finishes the function sets
io_flush to NULL even though there's still another request processing.

Stefan