perf evlist: Choose correct reading direction according to evlist->backward

Now we have evlist->backward to indicate the mmap direction. Make
perf_evlist__mmap_read() choose right direction automatically.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464183898-174512-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -777,7 +777,7 @@ broken_event:
 	return event;
 }
 
-union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+union perf_event *perf_evlist__mmap_read_forward(struct perf_evlist *evlist, int idx)
 {
 	struct perf_mmap *md = &evlist->mmap[idx];
 	u64 head;
@@ -832,6 +832,13 @@ perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
 	return perf_mmap__read(md, false, start, end, &md->prev);
 }
 
+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);
+}
+
 void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx)
 {
 	struct perf_mmap *md = &evlist->mmap[idx];

tools/perf/util/evlist.h

@@ -131,6 +131,8 @@ struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id);
 
 union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx);
 
+union perf_event *perf_evlist__mmap_read_forward(struct perf_evlist *evlist,
+						 int idx);
 union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist,
 						  int idx);
 void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx);