tracing: Consolidate max_tr into main trace_array structure

Currently, the way the latency tracers and snapshot feature works
is to have a separate trace_array called "max_tr" that holds the
snapshot buffer. For latency tracers, this snapshot buffer is used
to swap the running buffer with this buffer to save the current max
latency.

The only items needed for the max_tr is really just a copy of the buffer
itself, the per_cpu data pointers, the time_start timestamp that states
when the max latency was triggered, and the cpu that the max latency
was triggered on. All other fields in trace_array are unused by the
max_tr, making the max_tr mostly bloat.

This change removes the max_tr completely, and adds a new structure
called trace_buffer, that holds the buffer pointer, the per_cpu data
pointers, the time_start timestamp, and the cpu where the latency occurred.

The trace_array, now has two trace_buffers, one for the normal trace and
one for the max trace or snapshot. By doing this, not only do we remove
the bloat from the max_trace but the instances of traces can now use
their own snapshot feature and not have just the top level global_trace have
the snapshot feature and latency tracers for itself.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

13 files changed, 363 insertions, 286 deletions

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 71259e2b6b61..90a55054744c 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -72,7 +72,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 	bool blk_tracer = blk_tracer_enabled;
 
 	if (blk_tracer) {
-		buffer = blk_tr->buffer;
+		buffer = blk_tr->trace_buffer.buffer;
 		pc = preempt_count();
 		event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
 						  sizeof(*t) + len,
@@ -218,7 +218,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 	if (blk_tracer) {
 		tracing_record_cmdline(current);
 
-		buffer = blk_tr->buffer;
+		buffer = blk_tr->trace_buffer.buffer;
 		pc = preempt_count();
 		event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
 						  sizeof(*t) + pdu_len,
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c8a852a55db4..a08c127db865 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -195,27 +195,15 @@ cycle_t ftrace_now(int cpu)
 	u64 ts;
 
 	/* Early boot up does not have a buffer yet */
-	if (!global_trace.buffer)
+	if (!global_trace.trace_buffer.buffer)
 		return trace_clock_local();
 
-	ts = ring_buffer_time_stamp(global_trace.buffer, cpu);
-	ring_buffer_normalize_time_stamp(global_trace.buffer, cpu, &ts);
+	ts = ring_buffer_time_stamp(global_trace.trace_buffer.buffer, cpu);
+	ring_buffer_normalize_time_stamp(global_trace.trace_buffer.buffer, cpu, &ts);
 
 	return ts;
 }
 
-/*
- * The max_tr is used to snapshot the global_trace when a maximum
- * latency is reached. Some tracers will use this to store a maximum
- * trace while it continues examining live traces.
- *
- * The buffers for the max_tr are set up the same as the global_trace.
- * When a snapshot is taken, the link list of the max_tr is swapped
- * with the link list of the global_trace and the buffers are reset for
- * the global_trace so the tracing can continue.
- */
-static struct trace_array	max_tr;
-
 int tracing_is_enabled(void)
 {
 	return tracing_is_on();
@@ -339,8 +327,8 @@ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
  */
 void tracing_on(void)
 {
-	if (global_trace.buffer)
-		ring_buffer_record_on(global_trace.buffer);
+	if (global_trace.trace_buffer.buffer)
+		ring_buffer_record_on(global_trace.trace_buffer.buffer);
 	/*
 	 * This flag is only looked at when buffers haven't been
 	 * allocated yet. We don't really care about the race
@@ -361,8 +349,8 @@ EXPORT_SYMBOL_GPL(tracing_on);
  */
 void tracing_off(void)
 {
-	if (global_trace.buffer)
-		ring_buffer_record_off(global_trace.buffer);
+	if (global_trace.trace_buffer.buffer)
+		ring_buffer_record_off(global_trace.trace_buffer.buffer);
 	/*
 	 * This flag is only looked at when buffers haven't been
 	 * allocated yet. We don't really care about the race
@@ -378,8 +366,8 @@ EXPORT_SYMBOL_GPL(tracing_off);
  */
 int tracing_is_on(void)
 {
-	if (global_trace.buffer)
-		return ring_buffer_record_is_on(global_trace.buffer);
+	if (global_trace.trace_buffer.buffer)
+		return ring_buffer_record_is_on(global_trace.trace_buffer.buffer);
 	return !global_trace.buffer_disabled;
 }
 EXPORT_SYMBOL_GPL(tracing_is_on);
@@ -637,13 +625,14 @@ unsigned long __read_mostly	tracing_max_latency;
 static void
 __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
-	struct trace_array_cpu *data = per_cpu_ptr(tr->data, cpu);
-	struct trace_array_cpu *max_data;
+	struct trace_buffer *trace_buf = &tr->trace_buffer;
+	struct trace_buffer *max_buf = &tr->max_buffer;
+	struct trace_array_cpu *data = per_cpu_ptr(trace_buf->data, cpu);
+	struct trace_array_cpu *max_data = per_cpu_ptr(max_buf->data, cpu);
 
-	max_tr.cpu = cpu;
-	max_tr.time_start = data->preempt_timestamp;
+	max_buf->cpu = cpu;
+	max_buf->time_start = data->preempt_timestamp;
 
-	max_data = per_cpu_ptr(max_tr.data, cpu);
 	max_data->saved_latency = tracing_max_latency;
 	max_data->critical_start = data->critical_start;
 	max_data->critical_end = data->critical_end;
@@ -686,9 +675,9 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 
 	arch_spin_lock(&ftrace_max_lock);
 
-	buf = tr->buffer;
-	tr->buffer = max_tr.buffer;
-	max_tr.buffer = buf;
+	buf = tr->trace_buffer.buffer;
+	tr->trace_buffer.buffer = tr->max_buffer.buffer;
+	tr->max_buffer.buffer = buf;
 
 	__update_max_tr(tr, tsk, cpu);
 	arch_spin_unlock(&ftrace_max_lock);
@@ -716,7 +705,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 
 	arch_spin_lock(&ftrace_max_lock);
 
-	ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu);
+	ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->trace_buffer.buffer, cpu);
 
 	if (ret == -EBUSY) {
 		/*
@@ -725,7 +714,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 		 * the max trace buffer (no one writes directly to it)
 		 * and flag that it failed.
 		 */
-		trace_array_printk(&max_tr, _THIS_IP_,
+		trace_array_printk_buf(tr->max_buffer.buffer, _THIS_IP_,
 			"Failed to swap buffers due to commit in progress\n");
 	}
 
@@ -742,7 +731,7 @@ static void default_wait_pipe(struct trace_iterator *iter)
 	if (trace_buffer_iter(iter, iter->cpu_file))
 		return;
 
-	ring_buffer_wait(iter->tr->buffer, iter->cpu_file);
+	ring_buffer_wait(iter->trace_buffer->buffer, iter->cpu_file);
 }
 
 /**
@@ -803,17 +792,19 @@ int register_tracer(struct tracer *type)
 		 * internal tracing to verify that everything is in order.
 		 * If we fail, we do not register this tracer.
 		 */
-		tracing_reset_online_cpus(tr);
+		tracing_reset_online_cpus(&tr->trace_buffer);
 
 		tr->current_trace = type;
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 		if (type->use_max_tr) {
 			/* If we expanded the buffers, make sure the max is expanded too */
 			if (ring_buffer_expanded)
-				ring_buffer_resize(max_tr.buffer, trace_buf_size,
+				ring_buffer_resize(tr->max_buffer.buffer, trace_buf_size,
 						   RING_BUFFER_ALL_CPUS);
 			type->allocated_snapshot = true;
 		}
+#endif
 
 		/* the test is responsible for initializing and enabling */
 		pr_info("Testing tracer %s: ", type->name);
@@ -827,16 +818,18 @@ int register_tracer(struct tracer *type)
 			goto out;
 		}
 		/* Only reset on passing, to avoid touching corrupted buffers */
-		tracing_reset_online_cpus(tr);
+		tracing_reset_online_cpus(&tr->trace_buffer);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 		if (type->use_max_tr) {
 			type->allocated_snapshot = false;
 
 			/* Shrink the max buffer again */
 			if (ring_buffer_expanded)
-				ring_buffer_resize(max_tr.buffer, 1,
+				ring_buffer_resize(tr->max_buffer.buffer, 1,
 						   RING_BUFFER_ALL_CPUS);
 		}
+#endif
 
 		printk(KERN_CONT "PASSED\n");
 	}
@@ -870,9 +863,9 @@ int register_tracer(struct tracer *type)
 	return ret;
 }
 
-void tracing_reset(struct trace_array *tr, int cpu)
+void tracing_reset(struct trace_buffer *buf, int cpu)
 {
-	struct ring_buffer *buffer = tr->buffer;
+	struct ring_buffer *buffer = buf->buffer;
 
 	if (!buffer)
 		return;
@@ -886,9 +879,9 @@ void tracing_reset(struct trace_array *tr, int cpu)
 	ring_buffer_record_enable(buffer);
 }
 
-void tracing_reset_online_cpus(struct trace_array *tr)
+void tracing_reset_online_cpus(struct trace_buffer *buf)
 {
-	struct ring_buffer *buffer = tr->buffer;
+	struct ring_buffer *buffer = buf->buffer;
 	int cpu;
 
 	if (!buffer)
@@ -899,7 +892,7 @@ void tracing_reset_online_cpus(struct trace_array *tr)
 	/* Make sure all commits have finished */
 	synchronize_sched();
 
-	tr->time_start = ftrace_now(tr->cpu);
+	buf->time_start = ftrace_now(buf->cpu);
 
 	for_each_online_cpu(cpu)
 		ring_buffer_reset_cpu(buffer, cpu);
@@ -909,7 +902,7 @@ void tracing_reset_online_cpus(struct trace_array *tr)
 
 void tracing_reset_current(int cpu)
 {
-	tracing_reset(&global_trace, cpu);
+	tracing_reset(&global_trace.trace_buffer, cpu);
 }
 
 void tracing_reset_all_online_cpus(void)
@@ -918,7 +911,10 @@ void tracing_reset_all_online_cpus(void)
 
 	mutex_lock(&trace_types_lock);
 	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
-		tracing_reset_online_cpus(tr);
+		tracing_reset_online_cpus(&tr->trace_buffer);
+#ifdef CONFIG_TRACER_MAX_TRACE
+		tracing_reset_online_cpus(&tr->max_buffer);
+#endif
 	}
 	mutex_unlock(&trace_types_lock);
 }
@@ -988,13 +984,15 @@ void tracing_start(void)
 	/* Prevent the buffers from switching */
 	arch_spin_lock(&ftrace_max_lock);
 
-	buffer = global_trace.buffer;
+	buffer = global_trace.trace_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_enable(buffer);
 
-	buffer = max_tr.buffer;
+#ifdef CONFIG_TRACER_MAX_TRACE
+	buffer = global_trace.max_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_enable(buffer);
+#endif
 
 	arch_spin_unlock(&ftrace_max_lock);
 
@@ -1026,7 +1024,7 @@ static void tracing_start_tr(struct trace_array *tr)
 		goto out;
 	}
 
-	buffer = tr->buffer;
+	buffer = tr->trace_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_enable(buffer);
 
@@ -1053,13 +1051,15 @@ void tracing_stop(void)
 	/* Prevent the buffers from switching */
 	arch_spin_lock(&ftrace_max_lock);
 
-	buffer = global_trace.buffer;
+	buffer = global_trace.trace_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_disable(buffer);
 
-	buffer = max_tr.buffer;
+#ifdef CONFIG_TRACER_MAX_TRACE
+	buffer = global_trace.max_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_disable(buffer);
+#endif
 
 	arch_spin_unlock(&ftrace_max_lock);
 
@@ -1080,7 +1080,7 @@ static void tracing_stop_tr(struct trace_array *tr)
 	if (tr->stop_count++)
 		goto out;
 
-	buffer = tr->buffer;
+	buffer = tr->trace_buffer.buffer;
 	if (buffer)
 		ring_buffer_record_disable(buffer);
 
@@ -1246,7 +1246,7 @@ trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
 			  int type, unsigned long len,
 			  unsigned long flags, int pc)
 {
-	*current_rb = ftrace_file->tr->buffer;
+	*current_rb = ftrace_file->tr->trace_buffer.buffer;
 	return trace_buffer_lock_reserve(*current_rb,
 					 type, len, flags, pc);
 }
@@ -1257,7 +1257,7 @@ trace_current_buffer_lock_reserve(struct ring_buffer **current_rb,
 				  int type, unsigned long len,
 				  unsigned long flags, int pc)
 {
-	*current_rb = global_trace.buffer;
+	*current_rb = global_trace.trace_buffer.buffer;
 	return trace_buffer_lock_reserve(*current_rb,
 					 type, len, flags, pc);
 }
@@ -1296,7 +1296,7 @@ trace_function(struct trace_array *tr,
 	       int pc)
 {
 	struct ftrace_event_call *call = &event_function;
-	struct ring_buffer *buffer = tr->buffer;
+	struct ring_buffer *buffer = tr->trace_buffer.buffer;
 	struct ring_buffer_event *event;
 	struct ftrace_entry *entry;
 
@@ -1437,7 +1437,7 @@ void ftrace_trace_stack(struct ring_buffer *buffer, unsigned long flags,
 void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
 		   int pc)
 {
-	__ftrace_trace_stack(tr->buffer, flags, skip, pc, NULL);
+	__ftrace_trace_stack(tr->trace_buffer.buffer, flags, skip, pc, NULL);
 }
 
 /**
@@ -1453,7 +1453,8 @@ void trace_dump_stack(void)
 	local_save_flags(flags);
 
 	/* skipping 3 traces, seems to get us at the caller of this function */
-	__ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count(), NULL);
+	__ftrace_trace_stack(global_trace.trace_buffer.buffer, flags, 3,
+			     preempt_count(), NULL);
 }
 
 static DEFINE_PER_CPU(int, user_stack_count);
@@ -1623,7 +1624,7 @@ void trace_printk_init_buffers(void)
 	 * directly here. If the global_trace.buffer is already
 	 * allocated here, then this was called by module code.
 	 */
-	if (global_trace.buffer)
+	if (global_trace.trace_buffer.buffer)
 		tracing_start_cmdline_record();
 }
 
@@ -1683,7 +1684,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
 
 	local_save_flags(flags);
 	size = sizeof(*entry) + sizeof(u32) * len;
-	buffer = tr->buffer;
+	buffer = tr->trace_buffer.buffer;
 	event = trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
 					  flags, pc);
 	if (!event)
@@ -1706,27 +1707,12 @@ out:
 }
 EXPORT_SYMBOL_GPL(trace_vbprintk);
 
-int trace_array_printk(struct trace_array *tr,
-		       unsigned long ip, const char *fmt, ...)
-{
-	int ret;
-	va_list ap;
-
-	if (!(trace_flags & TRACE_ITER_PRINTK))
-		return 0;
-
-	va_start(ap, fmt);
-	ret = trace_array_vprintk(tr, ip, fmt, ap);
-	va_end(ap);
-	return ret;
-}
-
-int trace_array_vprintk(struct trace_array *tr,
-			unsigned long ip, const char *fmt, va_list args)
+static int
+__trace_array_vprintk(struct ring_buffer *buffer,
+		      unsigned long ip, const char *fmt, va_list args)
 {
 	struct ftrace_event_call *call = &event_print;
 	struct ring_buffer_event *event;
-	struct ring_buffer *buffer;
 	int len = 0, size, pc;
 	struct print_entry *entry;
 	unsigned long flags;
@@ -1754,7 +1740,6 @@ int trace_array_vprintk(struct trace_array *tr,
 
 	local_save_flags(flags);
 	size = sizeof(*entry) + len + 1;
-	buffer = tr->buffer;
 	event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
 					  flags, pc);
 	if (!event)
@@ -1775,6 +1760,42 @@ int trace_array_vprintk(struct trace_array *tr,
 	return len;
 }
 
+int trace_array_vprintk(struct trace_array *tr,
+			unsigned long ip, const char *fmt, va_list args)
+{
+	return __trace_array_vprintk(tr->trace_buffer.buffer, ip, fmt, args);
+}
+
+int trace_array_printk(struct trace_array *tr,
+		       unsigned long ip, const char *fmt, ...)
+{
+	int ret;
+	va_list ap;
+
+	if (!(trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
+	va_start(ap, fmt);
+	ret = trace_array_vprintk(tr, ip, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+
+int trace_array_printk_buf(struct ring_buffer *buffer,
+			   unsigned long ip, const char *fmt, ...)
+{
+	int ret;
+	va_list ap;
+
+	if (!(trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
+	va_start(ap, fmt);
+	ret = __trace_array_vprintk(buffer, ip, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+
 int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
 {
 	return trace_array_vprintk(&global_trace, ip, fmt, args);
@@ -1800,7 +1821,7 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts,
 	if (buf_iter)
 		event = ring_buffer_iter_peek(buf_iter, ts);
 	else
-		event = ring_buffer_peek(iter->tr->buffer, cpu, ts,
+		event = ring_buffer_peek(iter->trace_buffer->buffer, cpu, ts,
 					 lost_events);
 
 	if (event) {
@@ -1815,7 +1836,7 @@ static struct trace_entry *
 __find_next_entry(struct trace_iterator *iter, int *ent_cpu,
 		  unsigned long *missing_events, u64 *ent_ts)
 {
-	struct ring_buffer *buffer = iter->tr->buffer;
+	struct ring_buffer *buffer = iter->trace_buffer->buffer;
 	struct trace_entry *ent, *next = NULL;
 	unsigned long lost_events = 0, next_lost = 0;
 	int cpu_file = iter->cpu_file;
@@ -1892,7 +1913,7 @@ void *trace_find_next_entry_inc(struct trace_iterator *iter)
 
 static void trace_consume(struct trace_iterator *iter)
 {
-	ring_buffer_consume(iter->tr->buffer, iter->cpu, &iter->ts,
+	ring_buffer_consume(iter->trace_buffer->buffer, iter->cpu, &iter->ts,
 			    &iter->lost_events);
 }
 
@@ -1925,13 +1946,12 @@ static void *s_next(struct seq_file *m, void *v, loff_t *pos)
 
 void tracing_iter_reset(struct trace_iterator *iter, int cpu)
 {
-	struct trace_array *tr = iter->tr;
 	struct ring_buffer_event *event;
 	struct ring_buffer_iter *buf_iter;
 	unsigned long entries = 0;
 	u64 ts;
 
-	per_cpu_ptr(tr->data, cpu)->skipped_entries = 0;
+	per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = 0;
 
 	buf_iter = trace_buffer_iter(iter, cpu);
 	if (!buf_iter)
@@ -1945,13 +1965,13 @@ void tracing_iter_reset(struct trace_iterator *iter, int cpu)
 	 * by the timestamp being before the start of the buffer.
 	 */
 	while ((event = ring_buffer_iter_peek(buf_iter, &ts))) {
-		if (ts >= iter->tr->time_start)
+		if (ts >= iter->trace_buffer->time_start)
 			break;
 		entries++;
 		ring_buffer_read(buf_iter, NULL);
 	}
 
-	per_cpu_ptr(tr->data, cpu)->skipped_entries = entries;
+	per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = entries;
 }
 
 /*
@@ -1978,8 +1998,10 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 		*iter->trace = *tr->current_trace;
 	mutex_unlock(&trace_types_lock);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 	if (iter->snapshot && iter->trace->use_max_tr)
 		return ERR_PTR(-EBUSY);
+#endif
 
 	if (!iter->snapshot)
 		atomic_inc(&trace_record_cmdline_disabled);
@@ -2021,17 +2043,21 @@ static void s_stop(struct seq_file *m, void *p)
 {
 	struct trace_iterator *iter = m->private;
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 	if (iter->snapshot && iter->trace->use_max_tr)
 		return;
+#endif
 
 	if (!iter->snapshot)
 		atomic_dec(&trace_record_cmdline_disabled);
+
 	trace_access_unlock(iter->cpu_file);
 	trace_event_read_unlock();
 }
 
 static void
-get_total_entries(struct trace_array *tr, unsigned long *total, unsigned long *entries)
+get_total_entries(struct trace_buffer *buf,
+		  unsigned long *total, unsigned long *entries)
 {
 	unsigned long count;
 	int cpu;
@@ -2040,19 +2066,19 @@ get_total_entries(struct trace_array *tr, unsigned long *total, unsigned long *e
 	*entries = 0;
 
 	for_each_tracing_cpu(cpu) {
-		count = ring_buffer_entries_cpu(tr->buffer, 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(tr->data, cpu)->skipped_entries) {
-			count -= per_cpu_ptr(tr->data, cpu)->skipped_entries;
+		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(tr->buffer, cpu);
+				ring_buffer_overrun_cpu(buf->buffer, cpu);
 		*entries += count;
 	}
 }
@@ -2069,27 +2095,27 @@ static void print_lat_help_header(struct seq_file *m)
 	seq_puts(m, "#     \\   /      |||||  \\    |   /           \n");
 }
 
-static void print_event_info(struct trace_array *tr, struct seq_file *m)
+static void print_event_info(struct trace_buffer *buf, struct seq_file *m)
 {
 	unsigned long total;
 	unsigned long entries;
 
-	get_total_entries(tr, &total, &entries);
+	get_total_entries(buf, &total, &entries);
 	seq_printf(m, "# entries-in-buffer/entries-written: %lu/%lu   #P:%d\n",
 		   entries, total, num_online_cpus());
 	seq_puts(m, "#\n");
 }
 
-static void print_func_help_header(struct trace_array *tr, struct seq_file *m)
+static void print_func_help_header(struct trace_buffer *buf, struct seq_file *m)
 {
-	print_event_info(tr, m);
+	print_event_info(buf, m);
 	seq_puts(m, "#           TASK-PID   CPU#      TIMESTAMP  FUNCTION\n");
 	seq_puts(m, "#              | |       |          |         |\n");
 }
 
-static void print_func_help_header_irq(struct trace_array *tr, struct seq_file *m)
+static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file *m)
 {
-	print_event_info(tr, m);
+	print_event_info(buf, m);
 	seq_puts(m, "#                              _-----=> irqs-off\n");
 	seq_puts(m, "#                             / _----=> need-resched\n");
 	seq_puts(m, "#                            | / _---=> hardirq/softirq\n");
@@ -2103,8 +2129,8 @@ void
 print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 {
 	unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
-	struct trace_array *tr = iter->tr;
-	struct trace_array_cpu *data = per_cpu_ptr(tr->data, tr->cpu);
+	struct trace_buffer *buf = iter->trace_buffer;
+	struct trace_array_cpu *data = per_cpu_ptr(buf->data, buf->cpu);
 	struct tracer *type = iter->trace;
 	unsigned long entries;
 	unsigned long total;
@@ -2112,7 +2138,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 
 	name = type->name;
 
-	get_total_entries(tr, &total, &entries);
+	get_total_entries(buf, &total, &entries);
 
 	seq_printf(m, "# %s latency trace v1.1.5 on %s\n",
 		   name, UTS_RELEASE);
@@ -2123,7 +2149,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 		   nsecs_to_usecs(data->saved_latency),
 		   entries,
 		   total,
-		   tr->cpu,
+		   buf->cpu,
 #if defined(CONFIG_PREEMPT_NONE)
 		   "server",
 #elif defined(CONFIG_PREEMPT_VOLUNTARY)
@@ -2174,7 +2200,7 @@ static void test_cpu_buff_start(struct trace_iterator *iter)
 	if (cpumask_test_cpu(iter->cpu, iter->started))
 		return;
 
-	if (per_cpu_ptr(iter->tr->data, iter->cpu)->skipped_entries)
+	if (per_cpu_ptr(iter->trace_buffer->data, iter->cpu)->skipped_entries)
 		return;
 
 	cpumask_set_cpu(iter->cpu, iter->started);
@@ -2304,7 +2330,7 @@ int trace_empty(struct trace_iterator *iter)
 			if (!ring_buffer_iter_empty(buf_iter))
 				return 0;
 		} else {
-			if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
+			if (!ring_buffer_empty_cpu(iter->trace_buffer->buffer, cpu))
 				return 0;
 		}
 		return 1;
@@ -2316,7 +2342,7 @@ int trace_empty(struct trace_iterator *iter)
 			if (!ring_buffer_iter_empty(buf_iter))
 				return 0;
 		} else {
-			if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
+			if (!ring_buffer_empty_cpu(iter->trace_buffer->buffer, cpu))
 				return 0;
 		}
 	}
@@ -2394,9 +2420,9 @@ void trace_default_header(struct seq_file *m)
 	} else {
 		if (!(trace_flags & TRACE_ITER_VERBOSE)) {
 			if (trace_flags & TRACE_ITER_IRQ_INFO)
-				print_func_help_header_irq(iter->tr, m);
+				print_func_help_header_irq(iter->trace_buffer, m);
 			else
-				print_func_help_header(iter->tr, m);
+				print_func_help_header(iter->trace_buffer, m);
 		}
 	}
 }
@@ -2515,11 +2541,15 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 	if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL))
 		goto fail;
 
+	iter->tr = tr;
+
+#ifdef CONFIG_TRACER_MAX_TRACE
 	/* Currently only the top directory has a snapshot */
 	if (tr->current_trace->print_max || snapshot)
-		iter->tr = &max_tr;
+		iter->trace_buffer = &tr->max_buffer;
 	else
-		iter->tr = tr;
+#endif
+		iter->trace_buffer = &tr->trace_buffer;
 	iter->snapshot = snapshot;
 	iter->pos = -1;
 	mutex_init(&iter->mutex);
@@ -2530,7 +2560,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 		iter->trace->open(iter);
 
 	/* Annotate start of buffers if we had overruns */
-	if (ring_buffer_overruns(iter->tr->buffer))
+	if (ring_buffer_overruns(iter->trace_buffer->buffer))
 		iter->iter_flags |= TRACE_FILE_ANNOTATE;
 
 	/* Output in nanoseconds only if we are using a clock in nanoseconds. */
@@ -2544,7 +2574,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 	if (iter->cpu_file == RING_BUFFER_ALL_CPUS) {
 		for_each_tracing_cpu(cpu) {
 			iter->buffer_iter[cpu] =
-				ring_buffer_read_prepare(iter->tr->buffer, cpu);
+				ring_buffer_read_prepare(iter->trace_buffer->buffer, cpu);
 		}
 		ring_buffer_read_prepare_sync();
 		for_each_tracing_cpu(cpu) {
@@ -2554,7 +2584,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 	} else {
 		cpu = iter->cpu_file;
 		iter->buffer_iter[cpu] =
-			ring_buffer_read_prepare(iter->tr->buffer, cpu);
+			ring_buffer_read_prepare(iter->trace_buffer->buffer, cpu);
 		ring_buffer_read_prepare_sync();
 		ring_buffer_read_start(iter->buffer_iter[cpu]);
 		tracing_iter_reset(iter, cpu);
@@ -2593,12 +2623,7 @@ static int tracing_release(struct inode *inode, struct file *file)
 		return 0;
 
 	iter = m->private;
-
-	/* Only the global tracer has a matching max_tr */
-	if (iter->tr == &max_tr)
-		tr = &global_trace;
-	else
-		tr = iter->tr;
+	tr = iter->tr;
 
 	mutex_lock(&trace_types_lock);
 	for_each_tracing_cpu(cpu) {
@@ -2634,9 +2659,9 @@ static int tracing_open(struct inode *inode, struct file *file)
 		struct trace_array *tr = tc->tr;
 
 		if (tc->cpu == RING_BUFFER_ALL_CPUS)
-			tracing_reset_online_cpus(tr);
+			tracing_reset_online_cpus(&tr->trace_buffer);
 		else
-			tracing_reset(tr, tc->cpu);
+			tracing_reset(&tr->trace_buffer, tc->cpu);
 	}
 
 	if (file->f_mode & FMODE_READ) {
@@ -2805,13 +2830,13 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
 		 */
 		if (cpumask_test_cpu(cpu, tracing_cpumask) &&
 				!cpumask_test_cpu(cpu, tracing_cpumask_new)) {
-			atomic_inc(&per_cpu_ptr(tr->data, cpu)->disabled);
-			ring_buffer_record_disable_cpu(tr->buffer, cpu);
+			atomic_inc(&per_cpu_ptr(tr->trace_buffer.data, cpu)->disabled);
+			ring_buffer_record_disable_cpu(tr->trace_buffer.buffer, cpu);
 		}
 		if (!cpumask_test_cpu(cpu, tracing_cpumask) &&
 				cpumask_test_cpu(cpu, tracing_cpumask_new)) {
-			atomic_dec(&per_cpu_ptr(tr->data, cpu)->disabled);
-			ring_buffer_record_enable_cpu(tr->buffer, cpu);
+			atomic_dec(&per_cpu_ptr(tr->trace_buffer.data, cpu)->disabled);
+			ring_buffer_record_enable_cpu(tr->trace_buffer.buffer, cpu);
 		}
 	}
 	arch_spin_unlock(&ftrace_max_lock);
@@ -2930,9 +2955,9 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
 		trace_event_enable_cmd_record(enabled);
 
 	if (mask == TRACE_ITER_OVERWRITE) {
-		ring_buffer_change_overwrite(global_trace.buffer, enabled);
+		ring_buffer_change_overwrite(tr->trace_buffer.buffer, enabled);
 #ifdef CONFIG_TRACER_MAX_TRACE
-		ring_buffer_change_overwrite(max_tr.buffer, enabled);
+		ring_buffer_change_overwrite(tr->max_buffer.buffer, enabled);
 #endif
 	}
 
@@ -3116,42 +3141,44 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf,
 
 int tracer_init(struct tracer *t, struct trace_array *tr)
 {
-	tracing_reset_online_cpus(tr);
+	tracing_reset_online_cpus(&tr->trace_buffer);
 	return t->init(tr);
 }
 
-static void set_buffer_entries(struct trace_array *tr, unsigned long val)
+static void set_buffer_entries(struct trace_buffer *buf, unsigned long val)
 {
 	int cpu;
 	for_each_tracing_cpu(cpu)
-		per_cpu_ptr(tr->data, cpu)->entries = val;
+		per_cpu_ptr(buf->data, cpu)->entries = val;
 }
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 /* resize @tr's buffer to the size of @size_tr's entries */
-static int resize_buffer_duplicate_size(struct trace_array *tr,
-					struct trace_array *size_tr, int cpu_id)
+static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
+					struct trace_buffer *size_buf, int cpu_id)
 {
 	int cpu, ret = 0;
 
 	if (cpu_id == RING_BUFFER_ALL_CPUS) {
 		for_each_tracing_cpu(cpu) {
-			ret = ring_buffer_resize(tr->buffer,
-				 per_cpu_ptr(size_tr->data, cpu)->entries, cpu);
+			ret = ring_buffer_resize(trace_buf->buffer,
+				 per_cpu_ptr(size_buf->data, cpu)->entries, cpu);
 			if (ret < 0)
 				break;
-			per_cpu_ptr(tr->data, cpu)->entries =
-				per_cpu_ptr(size_tr->data, cpu)->entries;
+			per_cpu_ptr(trace_buf->data, cpu)->entries =
+				per_cpu_ptr(size_buf->data, cpu)->entries;
 		}
 	} else {
-		ret = ring_buffer_resize(tr->buffer,
-				 per_cpu_ptr(size_tr->data, cpu_id)->entries, cpu_id);
+		ret = ring_buffer_resize(trace_buf->buffer,
+				 per_cpu_ptr(size_buf->data, cpu_id)->entries, cpu_id);
 		if (ret == 0)
-			per_cpu_ptr(tr->data, cpu_id)->entries =
-				per_cpu_ptr(size_tr->data, cpu_id)->entries;
+			per_cpu_ptr(trace_buf->data, cpu_id)->entries =
+				per_cpu_ptr(size_buf->data, cpu_id)->entries;
 	}
 
 	return ret;
 }
+#endif /* CONFIG_TRACER_MAX_TRACE */
 
 static int __tracing_resize_ring_buffer(struct trace_array *tr,
 					unsigned long size, int cpu)
@@ -3166,20 +3193,22 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 	ring_buffer_expanded = 1;
 
 	/* May be called before buffers are initialized */
-	if (!tr->buffer)
+	if (!tr->trace_buffer.buffer)
 		return 0;
 
-	ret = ring_buffer_resize(tr->buffer, size, cpu);
+	ret = ring_buffer_resize(tr->trace_buffer.buffer, size, cpu);
 	if (ret < 0)
 		return ret;
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 	if (!(tr->flags & TRACE_ARRAY_FL_GLOBAL) ||
 	    !tr->current_trace->use_max_tr)
 		goto out;
 
-	ret = ring_buffer_resize(max_tr.buffer, size, cpu);
+	ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu);
 	if (ret < 0) {
-		int r = resize_buffer_duplicate_size(tr, tr, cpu);
+		int r = resize_buffer_duplicate_size(&tr->trace_buffer,
+						     &tr->trace_buffer, cpu);
 		if (r < 0) {
 			/*
 			 * AARGH! We are left with different
@@ -3202,15 +3231,17 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 	}
 
 	if (cpu == RING_BUFFER_ALL_CPUS)
-		set_buffer_entries(&max_tr, size);
+		set_buffer_entries(&tr->max_buffer, size);
 	else
-		per_cpu_ptr(max_tr.data, cpu)->entries = size;
+		per_cpu_ptr(tr->max_buffer.data, cpu)->entries = size;
 
  out:
+#endif /* CONFIG_TRACER_MAX_TRACE */
+
 	if (cpu == RING_BUFFER_ALL_CPUS)
-		set_buffer_entries(tr, size);
+		set_buffer_entries(&tr->trace_buffer, size);
 	else
-		per_cpu_ptr(tr->data, cpu)->entries = size;
+		per_cpu_ptr(tr->trace_buffer.data, cpu)->entries = size;
 
 	return ret;
 }
@@ -3277,7 +3308,9 @@ static int tracing_set_tracer(const char *buf)
 	static struct trace_option_dentry *topts;
 	struct trace_array *tr = &global_trace;
 	struct tracer *t;
+#ifdef CONFIG_TRACER_MAX_TRACE
 	bool had_max_tr;
+#endif
 	int ret = 0;
 
 	mutex_lock(&trace_types_lock);
@@ -3308,7 +3341,10 @@ static int tracing_set_tracer(const char *buf)
 	if (tr->current_trace->reset)
 		tr->current_trace->reset(tr);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
 	had_max_tr = tr->current_trace->allocated_snapshot;
+
+	/* Current trace needs to be nop_trace before synchronize_sched */
 	tr->current_trace = &nop_trace;
 
 	if (had_max_tr && !t->use_max_tr) {
@@ -3325,22 +3361,28 @@ static int tracing_set_tracer(const char *buf)
 		 * The max_tr ring buffer has some state (e.g. ring->clock) and
 		 * we want preserve it.
 		 */
-		ring_buffer_resize(max_tr.buffer, 1, RING_BUFFER_ALL_CPUS);
-		set_buffer_entries(&max_tr, 1);
-		tracing_reset_online_cpus(&max_tr);
+		ring_buffer_resize(tr->max_buffer.buffer, 1, RING_BUFFER_ALL_CPUS);
+		set_buffer_entries(&tr->max_buffer, 1);
+		tracing_reset_online_cpus(&tr->max_buffer);
 		tr->current_trace->allocated_snapshot = false;
 	}
+#else
+	tr->current_trace = &nop_trace;
+#endif
 	destroy_trace_option_files(topts);
 
 	topts = create_trace_option_files(tr, t);
+
+#ifdef CONFIG_TRACER_MAX_TRACE
 	if (t->use_max_tr && !had_max_tr) {
 		/* we need to make per cpu buffer sizes equivalent */
-		ret = resize_buffer_duplicate_size(&max_tr, &global_trace,
+		ret = resize_buffer_duplicate_size(&tr->max_buffer, &tr->trace_buffer,
 						   RING_BUFFER_ALL_CPUS);
 		if (ret < 0)
 			goto out;
 		t->allocated_snapshot = true;
 	}
+#endif
 
 	if (t->init) {
 		ret = tracer_init(t, tr);
@@ -3468,6 +3510,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 
 	iter->cpu_file = tc->cpu;
 	iter->tr = tc->tr;
+	iter->trace_buffer = &tc->tr->trace_buffer;
 	mutex_init(&iter->mutex);
 	filp->private_data = iter;
 
@@ -3518,7 +3561,7 @@ trace_poll(struct trace_iterator *iter, struct file *filp, poll_table *poll_tabl
 		 */
 		return POLLIN | POLLRDNORM;
 	else
-		return ring_buffer_poll_wait(iter->tr->buffer, iter-&