ftrace: print continue index fix

An item in the trace buffer that is bigger than one entry may be split
up using the TRACE_CONT entry. This makes it a virtual single entry.
The current code increments the iterator index even while traversing
TRACE_CONT entries, making it look like the iterator is further than
it actually is.

This patch adds code to not increment the iterator index while skipping
over TRACE_CONT entries.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -1117,9 +1117,8 @@ trace_entry_idx(struct trace_array *tr, struct trace_array_cpu *data,
 }
 
 /* Increment the index counter of an iterator by one */
-static void trace_iterator_increment(struct trace_iterator *iter, int cpu)
+static void __trace_iterator_increment(struct trace_iterator *iter, int cpu)
 {
-	iter->idx++;
 	iter->next_idx[cpu]++;
 	iter->next_page_idx[cpu]++;
 
@@ -1132,6 +1131,12 @@ static void trace_iterator_increment(struct trace_iterator *iter, int cpu)
 	}
 }
 
+static void trace_iterator_increment(struct trace_iterator *iter, int cpu)
+{
+	iter->idx++;
+	__trace_iterator_increment(iter, cpu);
+}
+
 static struct trace_entry *
 trace_entry_next(struct trace_array *tr, struct trace_array_cpu *data,
 		 struct trace_iterator *iter, int cpu)
@@ -1153,7 +1158,7 @@ trace_entry_next(struct trace_array *tr, struct trace_array_cpu *data,
 
 	/* find a real entry */
 	do {
-		trace_iterator_increment(iter, cpu);
+		__trace_iterator_increment(iter, cpu);
 		ent = trace_entry_idx(tr, tr->data[cpu], iter, cpu);
 	} while (ent && ent->type != TRACE_CONT);
 
@@ -1187,7 +1192,7 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu, int inc)
 				ent = trace_entry_next(tr, data, iter, cpu);
 			else {
 				while (ent && ent->type == TRACE_CONT) {
-					trace_iterator_increment(iter, cpu);
+					__trace_iterator_increment(iter, cpu);
 					ent = trace_entry_idx(tr, tr->data[cpu],
 							      iter, cpu);
 				}
@@ -1566,7 +1571,7 @@ trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter)
 
 	do {
 		trace_seq_printf(s, "%s", ent->cont.buf);
-		trace_iterator_increment(iter, iter->cpu);
+		__trace_iterator_increment(iter, iter->cpu);
 		ent = trace_entry_idx(tr, data, iter, iter->cpu);
 	} while (ent && ent->type == TRACE_CONT);
 }