From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 28 Jan 2015 22:07:35 +0000 (-0500)
Subject: Fix: lazy-mmap() streams when flushing
X-Git-Tag: v2.0.0-pre1~1424
X-Git-Url: http://git.efficios.com/?p=babeltrace.git;a=commitdiff_plain;h=28362f2bcb7fe869c6bc1b078ceab41483fd69a6

Fix: lazy-mmap() streams when flushing

This fixes an issue when empty streams are created as the stream
creation will mmap() the file in preparation for the first event.

This results in "empty" stream files ending up with a non-zero size
which is invalid since no packet headers are found by the reader.

This change ensures that stream files are only mmap'ed on the first
stream flush and that empty streams are stored as size-0 files.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
index 40da01da..5436c2a7 100644
--- a/formats/ctf/ctf.c
+++ b/formats/ctf/ctf.c
@@ -768,8 +768,6 @@ int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor *trace,
 		pos->parent.rw_table = write_dispatch_table;
 		pos->parent.event_cb = ctf_write_event;
 		pos->parent.trace = trace;
-		if (fd >= 0)
-			ctf_packet_seek(&pos->parent, 0, SEEK_SET);	/* position for write */
 		break;
 	default:
 		assert(0);
diff --git a/formats/ctf/ir/stream.c b/formats/ctf/ir/stream.c
index 6a71466c..1d14abd6 100644
--- a/formats/ctf/ir/stream.c
+++ b/formats/ctf/ir/stream.c
@@ -702,10 +702,8 @@ int bt_ctf_stream_flush(struct bt_ctf_stream *stream)
 		goto end;
 	}
 
-	if (stream->flushed_packet_count) {
-		/* ctf_init_pos has already initialized the first packet */
-		ctf_packet_seek(&stream->pos.parent, 0, SEEK_CUR);
-	}
+	/* mmap the next packet */
+	ctf_packet_seek(&stream->pos.parent, 0, SEEK_CUR);
 
 	ret = bt_ctf_field_serialize(stream->packet_header, &stream->pos);
 	if (ret) {