perf evlist: Drop evlist->backward

Now there's no real user of evlist->backward. Drop it. We are going to
use evlist->backward_mmap as a container for backward ring buffer.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: He Kuang <hekuang@huawei.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468485287-33422-10-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/backward-ring-buffer.c

@@ -101,7 +101,6 @@ int test__backward_ring_buffer(int subtest __maybe_unused)
 		return TEST_FAIL;
 	}
 
-	evlist->backward = true;
 	err = perf_evlist__create_maps(evlist, &opts.target);
 	if (err < 0) {
 		pr_debug("Not enough memory to create thread/cpu maps\n");

tools/perf/util/evlist.c

@@ -44,7 +44,6 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,
 	perf_evlist__set_maps(evlist, cpus, threads);
 	fdarray__init(&evlist->pollfd, 64);
 	evlist->workload.pid = -1;
-	evlist->backward = false;
 }
 
 struct perf_evlist *perf_evlist__new(void)
@@ -867,9 +866,7 @@ union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist, in
 
 union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
 {
-	if (!evlist->backward)
-		return perf_evlist__mmap_read_forward(evlist, idx);
-	return perf_evlist__mmap_read_backward(evlist, idx);
+	return perf_evlist__mmap_read_forward(evlist, idx);
 }
 
 void perf_mmap__read_catchup(struct perf_mmap *md)

tools/perf/util/evlist.h

@@ -50,7 +50,6 @@ struct perf_evlist {
 	bool		 overwrite;
 	bool		 enabled;
 	bool		 has_user_cpus;
-	bool		 backward;
 	size_t		 mmap_len;
 	int		 id_pos;
 	int		 is_pos;