virtio-blk: add virtio_blk_handle_read trace event

There already exists a virtio_blk_handle_write trace event as well as
completion events.  Add the virtio_blk_handle_read event so it's easy to
trace virtio-blk requests for both read and write operations.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/virtio-blk.c

@@ -346,6 +346,8 @@ static void virtio_blk_handle_read(VirtIOBlockReq *req)
 
     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
 
+    trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
+
     if (sector & req->dev->sector_mask) {
         virtio_blk_rw_complete(req, -EIO);
         return;

trace-events

@@ -83,6 +83,7 @@ qmp_block_stream(void *bs, void *job) "bs %p job %p"
 virtio_blk_req_complete(void *req, int status) "req %p status %d"
 virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
 virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
+virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
 
 # posix-aio-compat.c
 paio_submit(void *acb, void *opaque, int64_t sector_num, int nb_sectors, int type) "acb %p opaque %p sector_num %"PRId64" nb_sectors %d type %d"