Re: [PATCH 04/13] util/vhost-user-server: rename refcount to in_flight counter

[Paolo Bonzini <pbonzini@redhat.com>]

On 4/3/23 20:29, Stefan Hajnoczi wrote:
> The VuServer object has a refcount field and ref/unref APIs. The name is
> confusing because it's actually an in-flight request counter instead of
> a refcount.
> 
> Normally a refcount destroys the object upon reaching zero. The VuServer
> counter is used to wake up the vhost-user coroutine when there are no
> more requests.
> 
> Avoid confusing by renaming refcount and ref/unref to in_flight and
> inc/dec.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   include/qemu/vhost-user-server.h     |  6 +++---
>   block/export/vhost-user-blk-server.c | 11 +++++++----
>   util/vhost-user-server.c             | 14 +++++++-------
>   3 files changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/include/qemu/vhost-user-server.h b/include/qemu/vhost-user-server.h
> index 25c72433ca..bc0ac9ddb6 100644
> --- a/include/qemu/vhost-user-server.h
> +++ b/include/qemu/vhost-user-server.h
> @@ -41,7 +41,7 @@ typedef struct {
>       const VuDevIface *vu_iface;
>   
>       /* Protected by ctx lock */
> -    unsigned int refcount;
> +    unsigned int in_flight;
>       bool wait_idle;
>       VuDev vu_dev;
>       QIOChannel *ioc; /* The I/O channel with the client */
> @@ -60,8 +60,8 @@ bool vhost_user_server_start(VuServer *server,
>   
>   void vhost_user_server_stop(VuServer *server);
>   
> -void vhost_user_server_ref(VuServer *server);
> -void vhost_user_server_unref(VuServer *server);
> +void vhost_user_server_inc_in_flight(VuServer *server);
> +void vhost_user_server_dec_in_flight(VuServer *server);
>   
>   void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx);
>   void vhost_user_server_detach_aio_context(VuServer *server);
> diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c
> index 3409d9e02e..e93f2ed6b4 100644
> --- a/block/export/vhost-user-blk-server.c
> +++ b/block/export/vhost-user-blk-server.c
> @@ -49,7 +49,10 @@ static void vu_blk_req_complete(VuBlkReq *req, size_t in_len)
>       free(req);
>   }
>   
> -/* Called with server refcount increased, must decrease before returning */
> +/*
> + * Called with server in_flight counter increased, must decrease before
> + * returning.
> + */
>   static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
>   {
>       VuBlkReq *req = opaque;
> @@ -67,12 +70,12 @@ static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
>                                       in_num, out_num);
>       if (in_len < 0) {
>           free(req);
> -        vhost_user_server_unref(server);
> +        vhost_user_server_dec_in_flight(server);
>           return;
>       }
>   
>       vu_blk_req_complete(req, in_len);
> -    vhost_user_server_unref(server);
> +    vhost_user_server_dec_in_flight(server);
>   }
>   
>   static void vu_blk_process_vq(VuDev *vu_dev, int idx)
> @@ -94,7 +97,7 @@ static void vu_blk_process_vq(VuDev *vu_dev, int idx)
>           Coroutine *co =
>               qemu_coroutine_create(vu_blk_virtio_process_req, req);
>   
> -        vhost_user_server_ref(server);
> +        vhost_user_server_inc_in_flight(server);
>           qemu_coroutine_enter(co);
>       }
>   }
> diff --git a/util/vhost-user-server.c b/util/vhost-user-server.c
> index 5b6216069c..1622f8cfb3 100644
> --- a/util/vhost-user-server.c
> +++ b/util/vhost-user-server.c
> @@ -75,16 +75,16 @@ static void panic_cb(VuDev *vu_dev, const char *buf)
>       error_report("vu_panic: %s", buf);
>   }
>   
> -void vhost_user_server_ref(VuServer *server)
> +void vhost_user_server_inc_in_flight(VuServer *server)
>   {
>       assert(!server->wait_idle);
> -    server->refcount++;
> +    server->in_flight++;
>   }
>   
> -void vhost_user_server_unref(VuServer *server)
> +void vhost_user_server_dec_in_flight(VuServer *server)
>   {
> -    server->refcount--;
> -    if (server->wait_idle && !server->refcount) {
> +    server->in_flight--;
> +    if (server->wait_idle && !server->in_flight) {
>           aio_co_wake(server->co_trip);
>       }
>   }
> @@ -192,13 +192,13 @@ static coroutine_fn void vu_client_trip(void *opaque)
>           /* Keep running */
>       }
>   
> -    if (server->refcount) {
> +    if (server->in_flight) {
>           /* Wait for requests to complete before we can unmap the memory */
>           server->wait_idle = true;
>           qemu_coroutine_yield();
>           server->wait_idle = false;
>       }
> -    assert(server->refcount == 0);
> +    assert(server->in_flight == 0);
>   
>       vu_deinit(vu_dev);
>   

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>