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 <[e-mail]>
Cc: He Kuang <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Zefan Li <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/evlist.c

···
 	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;
···
 		end = head + md->mask + 1;
 
 	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)

tools/perf/util/evlist.h

···
 
 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);