block/io_uring: adds userspace completion polling

Signed-off-by: NAarushi Mehta <mehta.aaru20@gmail.com>
Acked-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200120141858.587874-11-stefanha@redhat.com
Message-Id: <20200120141858.587874-11-stefanha@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/io_uring.c

@@ -274,6 +274,21 @@ static void qemu_luring_completion_cb(void *opaque)
     luring_process_completions_and_submit(s);
 }
 
+static bool qemu_luring_poll_cb(void *opaque)
+{
+    LuringState *s = opaque;
+    struct io_uring_cqe *cqes;
+
+    if (io_uring_peek_cqe(&s->ring, &cqes) == 0) {
+        if (cqes) {
+            luring_process_completions_and_submit(s);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 static void ioq_init(LuringQueue *io_q)
 {
     QSIMPLEQ_INIT(&io_q->submit_queue);
@@ -387,7 +402,7 @@ void luring_attach_aio_context(LuringState *s, AioContext *new_context)
     s->aio_context = new_context;
     s->completion_bh = aio_bh_new(new_context, qemu_luring_completion_bh, s);
     aio_set_fd_handler(s->aio_context, s->ring.ring_fd, false,
-                       qemu_luring_completion_cb, NULL, NULL, s);
+                       qemu_luring_completion_cb, NULL, qemu_luring_poll_cb, s);
 }
 
 LuringState *luring_init(Error **errp)