perf session: Introduce reader return codes

Add READER_OK and READER_NODATA return codes to make the code more
clear.
Suggested-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Reviewed-by: Riccardo Mancini <rickyman7@gmail.com>
Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Tested-by: Riccardo Mancini <rickyman7@gmail.com>
Acked-by: Namhyung Kim <namhyung@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Antonov <alexander.antonov@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/5fca481e91c3c5d2ba033d4c6e9b969f8033ab0f.1634113027.git.alexey.v.bayduraev@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/session.c

@@ -2263,12 +2263,17 @@ reader__mmap(struct reader *rd, struct perf_session *session)
 	return 0;
 }
 
+enum {
+	READER_OK,
+	READER_NODATA,
+};
+
 static int
 reader__read_event(struct reader *rd, struct perf_session *session,
 		   struct ui_progress *prog)
 {
 	u64 size;
-	int err = 0;
+	int err = READER_OK;
 	union perf_event *event;
 	s64 skip;
 
@@ -2278,7 +2283,7 @@ reader__read_event(struct reader *rd, struct perf_session *session,
 		return PTR_ERR(event);
 
 	if (!event)
-		return 1;
+		return READER_NODATA;
 
 	size = event->header.size;
 
@@ -2330,7 +2335,7 @@ reader__process_events(struct reader *rd, struct perf_session *session,
 	err = reader__read_event(rd, session, prog);
 	if (err < 0)
 		goto out;
-	else if (err == 1)
+	else if (err == READER_NODATA)
 		goto remap;
 
 	if (session_done())