+ goto end;
+
+error_snapshot:
+ /* Clean up copied sockets so this output can use some other later on. */
+ consumer_destroy_output_sockets(output->consumer);
+error:
+end:
+ return status;
+}
+
+/*
+ * Record a UST snapshot.
+ *
+ * Returns LTTNG_OK on success or a LTTNG_ERR error code.
+ */
+static enum lttng_error_code record_ust_snapshot(struct ltt_ust_session *usess,
+ const struct snapshot_output *output,
+ const struct ltt_session *session, int wait,
+ uint64_t nb_packets_per_stream)
+{
+ int ret;
+ enum lttng_error_code status;
+
+ assert(usess);
+ assert(output);
+ assert(session);
+
+ /*
+ * Copy UST session sockets so we can communicate with the right
+ * consumer for the snapshot record command.
+ */
+ ret = consumer_copy_sockets(output->consumer, usess->consumer);
+ if (ret < 0) {
+ status = LTTNG_ERR_NOMEM;
+ goto error;
+ }
+
+ status = set_relayd_for_snapshot(usess->consumer, output, session);
+ if (status != LTTNG_OK) {
+ goto error_snapshot;
+ }
+
+ status = ust_app_snapshot_record(usess, output, wait,
+ nb_packets_per_stream);
+ if (status != LTTNG_OK) {
+ goto error_snapshot;
+ }
+
+ goto end;
+
+error_snapshot:
+ /* Clean up copied sockets so this output can use some other later on. */
+ consumer_destroy_output_sockets(output->consumer);
+error:
+end:
+ return status;
+}
+
+static
+uint64_t get_session_size_one_more_packet_per_stream(
+ const struct ltt_session *session, uint64_t cur_nr_packets)
+{
+ uint64_t tot_size = 0;
+
+ if (session->kernel_session) {
+ struct ltt_kernel_channel *chan;
+ const struct ltt_kernel_session *ksess =
+ session->kernel_session;
+
+ cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+ if (cur_nr_packets >= chan->channel->attr.num_subbuf) {
+ /*
+ * Don't take channel into account if we
+ * already grab all its packets.
+ */
+ continue;
+ }
+ tot_size += chan->channel->attr.subbuf_size
+ * chan->stream_count;
+ }
+ }
+
+ if (session->ust_session) {
+ const struct ltt_ust_session *usess = session->ust_session;
+
+ tot_size += ust_app_get_size_one_more_packet_per_stream(usess,
+ cur_nr_packets);
+ }
+
+ return tot_size;
+}
+
+/*
+ * Calculate the number of packets we can grab from each stream that
+ * fits within the overall snapshot max size.
+ *
+ * Returns -1 on error, 0 means infinite number of packets, else > 0 is
+ * the number of packets per stream.
+ *
+ * TODO: this approach is not perfect: we consider the worse case
+ * (packet filling the sub-buffers) as an upper bound, but we could do
+ * better if we do this calculation while we actually grab the packet
+ * content: we would know how much padding we don't actually store into
+ * the file.
+ *
+ * This algorithm is currently bounded by the number of packets per
+ * stream.
+ *
+ * Since we call this algorithm before actually grabbing the data, it's
+ * an approximation: for instance, applications could appear/disappear
+ * in between this call and actually grabbing data.
+ */
+static
+int64_t get_session_nb_packets_per_stream(const struct ltt_session *session,
+ uint64_t max_size)
+{
+ int64_t size_left;
+ uint64_t cur_nb_packets = 0;
+
+ if (!max_size) {
+ return 0; /* Infinite */
+ }
+
+ size_left = max_size;
+ for (;;) {
+ uint64_t one_more_packet_tot_size;
+
+ one_more_packet_tot_size = get_session_size_one_more_packet_per_stream(
+ session, cur_nb_packets);
+ if (!one_more_packet_tot_size) {
+ /* We are already grabbing all packets. */
+ break;
+ }
+ size_left -= one_more_packet_tot_size;
+ if (size_left < 0) {
+ break;
+ }
+ cur_nb_packets++;
+ }
+ if (!cur_nb_packets) {
+ /* Not enough room to grab one packet of each stream, error. */
+ return -1;
+ }
+ return cur_nb_packets;
+}
+
+static
+enum lttng_error_code snapshot_record(struct ltt_session *session,
+ const struct snapshot_output *snapshot_output, int wait)
+{
+ int fmt_ret;
+ int64_t nb_packets_per_stream;
+ char snapshot_chunk_name[LTTNG_NAME_MAX];
+ enum lttng_error_code ret = LTTNG_OK;
+ struct lttng_trace_chunk *snapshot_trace_chunk;
+
+ fmt_ret = snprintf(snapshot_chunk_name, sizeof(snapshot_chunk_name),
+ "%s-%s-%" PRIu64,
+ snapshot_output->name,
+ snapshot_output->datetime,
+ snapshot_output->nb_snapshot);
+ if (fmt_ret < 0 || fmt_ret >= sizeof(snapshot_chunk_name)) {
+ ERR("Failed to format snapshot name");
+ ret = LTTNG_ERR_INVALID;
+ goto end;
+ }
+ DBG("Recording snapshot \"%s\" for session \"%s\" with chunk name \"%s\"",
+ snapshot_output->name, session->name,
+ snapshot_chunk_name);
+ snapshot_trace_chunk = session_create_new_trace_chunk(session,
+ snapshot_output_get_base_path(snapshot_output),
+ snapshot_chunk_name);
+ if (!snapshot_trace_chunk) {
+ ret = LTTNG_ERR_CREATE_DIR_FAIL;
+ goto end;
+ }
+ assert(!session->current_trace_chunk);
+ ret = session_set_trace_chunk(session, snapshot_trace_chunk, NULL);
+ lttng_trace_chunk_put(snapshot_trace_chunk);
+ snapshot_trace_chunk = NULL;
+ if (ret) {
+ ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER;
+ goto end;
+ }
+
+ nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+ snapshot_output->max_size);
+ if (nb_packets_per_stream < 0) {
+ ret = LTTNG_ERR_MAX_SIZE_INVALID;
+ goto end;
+ }
+
+ if (session->kernel_session) {
+ ret = record_kernel_snapshot(session->kernel_session,
+ snapshot_output, session,
+ wait, nb_packets_per_stream);
+ if (ret != LTTNG_OK) {
+ goto end;
+ }
+ }
+
+ if (session->ust_session) {
+ ret = record_ust_snapshot(session->ust_session,
+ snapshot_output, session,
+ wait, nb_packets_per_stream);
+ if (ret != LTTNG_OK) {
+ goto end;
+ }
+ }
+
+ if (session_close_trace_chunk(session, session->current_trace_chunk)) {
+ /*
+ * Don't goto end; make sure the chunk is closed for the session
+ * to allow future snapshots.
+ */
+ ERR("Failed to close snapshot trace chunk of session \"%s\"",
+ session->name);
+ ret = -1;
+ }
+ if (session_set_trace_chunk(session, NULL, NULL)) {
+ ERR("Failed to release the current trace chunk of session \"%s\"",
+ session->name);
+ ret = -1;
+ }
+end:
+ return ret;