Fix: compat ioctl for flush/get metadata version

Unlike the non-compat version, the compat ioctl lttng ABI code for the
ring buffer flush operation does not invoke
lttng_metadata_output_channel before calling the ring buffer operation.
This could lead to incomplete metadata on 64-bit kernels running with
32-bit lttng userland.

There is also a discrepancy between the non-compat and compat code: the
GET_METADATA_VERSION operation is performed before calling the ring
buffer code. Ensure both non-compat and compat code are alike.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-abi.c b/lttng-abi.c
index c14cc82b2baca8aa6e2012a6f46d8079fa58f2ec..87465189060edd4122cc9f8c5ad87c3fe218b6f1 100644 (file)
--- a/lttng-abi.c
+++ b/lttng-abi.c
@@ -757,6 +757,27 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp,
                 */
                return -ENOSYS;
        }
+       case RING_BUFFER_FLUSH:
+       {
+               struct lttng_metadata_stream *stream = filp->private_data;
+               struct lib_ring_buffer *buf = stream->priv;
+               struct channel *chan = buf->backend.chan;
+
+               /*
+                * Before doing the actual ring buffer flush, write up to one
+                * packet of metadata in the ring buffer.
+                */
+               ret = lttng_metadata_output_channel(stream, chan);
+               if (ret < 0)
+                       goto err;
+               break;
+       }
+       case RING_BUFFER_GET_METADATA_VERSION:
+       {
+               struct lttng_metadata_stream *stream = filp->private_data;
+
+               return put_u64(stream->version, arg);
+       }
        default:
                break;
        }
@@ -774,12 +795,6 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp,
                                cmd, arg);
                break;
        }
-       case RING_BUFFER_GET_METADATA_VERSION:
-       {
-               struct lttng_metadata_stream *stream = filp->private_data;
-
-               return put_u64(stream->version, arg);
-       }
        default:
                break;
        }