[PATCH v6 2/3] tracing: Add trace_total_entries() / trace_total_entries_cpu()

[Douglas Anderson]

These two new exported functions will be used in a future patch by
kdb_ftdump() to quickly skip all but the last few trace entries.

Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
---

Changes in v6:
- Add Daniel Thompson Ack.

Changes in v5: None
Changes in v4:
- trace_total_entries() / trace_total_entries_cpu() new for v4

Changes in v3: None

 kernel/trace/trace.c | 65 ++++++++++++++++++++++++++++++++++----------
 kernel/trace/trace.h |  3 ++
 2 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ccd759eaad79..7afc90f82e53 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3490,34 +3490,69 @@ static void s_stop(struct seq_file *m, void *p)
 	trace_event_read_unlock();
 }
 
+static void
+get_total_entries_cpu(struct trace_buffer *buf, unsigned long *total,
+		      unsigned long *entries, int cpu)
+{
+	unsigned long count;
+
+	count = ring_buffer_entries_cpu(buf->buffer, cpu);
+	/*
+	 * If this buffer has skipped entries, then we hold all
+	 * entries for the trace and we need to ignore the
+	 * ones before the time stamp.
+	 */
+	if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
+		count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
+		/* total is the same as the entries */
+		*total = count;
+	} else
+		*total = count +
+			ring_buffer_overrun_cpu(buf->buffer, cpu);
+	*entries = count;
+}
+
 static void
 get_total_entries(struct trace_buffer *buf,
 		  unsigned long *total, unsigned long *entries)
 {
-	unsigned long count;
+	unsigned long t, e;
 	int cpu;
 
 	*total = 0;
 	*entries = 0;
 
 	for_each_tracing_cpu(cpu) {
-		count = ring_buffer_entries_cpu(buf->buffer, cpu);
-		/*
-		 * If this buffer has skipped entries, then we hold all
-		 * entries for the trace and we need to ignore the
-		 * ones before the time stamp.
-		 */
-		if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
-			count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
-			/* total is the same as the entries */
-			*total += count;
-		} else
-			*total += count +
-				ring_buffer_overrun_cpu(buf->buffer, cpu);
-		*entries += count;
+		get_total_entries_cpu(buf, &t, &e, cpu);
+		*total += t;
+		*entries += e;
 	}
 }
 
+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu)
+{
+	unsigned long total, entries;
+
+	if (!tr)
+		tr = &global_trace;
+
+	get_total_entries_cpu(&tr->trace_buffer, &total, &entries, cpu);
+
+	return entries;
+}
+
+unsigned long trace_total_entries(struct trace_array *tr)
+{
+	unsigned long total, entries;
+
+	if (!tr)
+		tr = &global_trace;
+
+	get_total_entries(&tr->trace_buffer, &total, &entries);
+
+	return entries;
+}
+
 static void print_lat_help_header(struct seq_file *m)
 {
 	seq_puts(m, "#                  _------=> CPU#            \n"
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d80cee49e0eb..4562b30eda9d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -719,6 +719,9 @@ void trace_init_global_iter(struct trace_iterator *iter);
 
 void tracing_iter_reset(struct trace_iterator *iter, int cpu);
 
+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu);
+unsigned long trace_total_entries(struct trace_array *tr);
+
 void trace_function(struct trace_array *tr,
 		    unsigned long ip,
 		    unsigned long parent_ip,
-- 
2.21.0.225.g810b269d1ac-goog