perf record: Fix perf.data size in no-buildid mode

The size of perf.data is missing update in no-buildid mode, which gives
wrong output result.

Before this patch:

  $ perf.perf record -B -e syscalls:sys_enter_open uname
  Linux
  [ perf record: Woken up 1 times to  write data ]
  [ perf record: Captured and wrote 0.000 MB perf.data ]

After this patch:

  $ perf.perf record -B -e syscalls:sys_enter_open uname
  Linux
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.001 MB perf.data ]

Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1432819050-30511-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -345,12 +345,9 @@ static int process_buildids(struct record *rec)
 	struct perf_data_file *file  = &rec->file;
 	struct perf_session *session = rec->session;
 
-	u64 size = lseek(perf_data_file__fd(file), 0, SEEK_CUR);
+	if (file->size == 0)
-	if (size == 0)
 		return 0;
 
-	file->size = size;
-
 	/*
 	 * During this process, it'll load kernel map and replace the
 	 * dso->long_name to a real pathname it found.  In this case
@@ -719,6 +716,7 @@ out_child:
 
 	if (!err && !file->is_pipe) {
 		rec->session->header.data_size += rec->bytes_written;
+		file->size = lseek(perf_data_file__fd(file), 0, SEEK_CUR);
 
 		if (!rec->no_buildid) {
 			process_buildids(rec);