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


From: Paolo Bonzini
Subject: Re: [PATCH 04/13] util/vhost-user-server: rename refcount to in_flight counter
Date: Tue, 4 Apr 2023 15:39:31 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0

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>




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