tests/test-bdrv-drain: use QEMU_IOVEC_INIT_BUF

Use new QEMU_IOVEC_INIT_BUF() instead of
qemu_iovec_init_external( ... , 1), which simplifies the code.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190218140926.333779-15-vsementsov@virtuozzo.com
Message-Id: <20190218140926.333779-15-vsementsov@virtuozzo.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/test-bdrv-drain.c

@@ -204,12 +204,7 @@ static void test_drv_cb_common(enum drain_type drain_type, bool recursive)
     BlockAIOCB *acb;
     int aio_ret;
 
-    QEMUIOVector qiov;
-    struct iovec iov = {
-        .iov_base = NULL,
-        .iov_len = 0,
-    };
-    qemu_iovec_init_external(&qiov, &iov, 1);
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, 0);
 
     blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
     bs = bdrv_new_open_driver(&bdrv_test, "test-node", BDRV_O_RDWR,
@@ -670,12 +665,7 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
     AioContext *ctx_a = iothread_get_aio_context(a);
     AioContext *ctx_b = iothread_get_aio_context(b);
 
-    QEMUIOVector qiov;
-    struct iovec iov = {
-        .iov_base = NULL,
-        .iov_len = 0,
-    };
-    qemu_iovec_init_external(&qiov, &iov, 1);
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, 0);
 
     /* bdrv_drain_all() may only be called from the main loop thread */
     if (drain_type == BDRV_DRAIN_ALL && drain_thread != 0) {
@@ -1148,13 +1138,7 @@ static void coroutine_fn test_co_delete_by_drain(void *opaque)
     BlockDriverState *bs = blk_bs(blk);
     BDRVTestTopState *tts = bs->opaque;
     void *buffer = g_malloc(65536);
-    QEMUIOVector qiov;
-    struct iovec iov = {
-        .iov_base = buffer,
-        .iov_len  = 65536,
-    };
-
-    qemu_iovec_init_external(&qiov, &iov, 1);
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buffer, 65536);
 
     /* Pretend some internal write operation from parent to child.
      * Important: We have to read from the child, not from the parent!
@@ -1365,12 +1349,7 @@ static void test_detach_indirect(bool by_parent_cb)
     BdrvChild *child_a, *child_b;
     BlockAIOCB *acb;
 
-    QEMUIOVector qiov;
-    struct iovec iov = {
-        .iov_base = NULL,
-        .iov_len = 0,
-    };
-    qemu_iovec_init_external(&qiov, &iov, 1);
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, 0);
 
     if (!by_parent_cb) {
         detach_by_driver_cb_role = child_file;