[PATCH v1 6/9] ring-buffer: Introduce rb_start_write() and rb_end_write()

[Vincent Donnefort <vdonnefort@google.com>]

Factor the common write-context entry (preemption disabling, disabled
checks, cpumask testing, recursive locking) and exit paths shared by
ring_buffer_lock_reserve() and ring_buffer_write() into a pair of
functions: rb_start_write() and rb_end_write().

No functional change intended.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
---
 kernel/trace/ring_buffer.c | 106 ++++++++++++++++++-------------------
 1 file changed, 51 insertions(+), 55 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9834f9dae440..02d3cc193d1e 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4495,6 +4495,45 @@ trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
 		cpu_buffer->current_context - (1 << cpu_buffer->nest);
 }
 
+static __always_inline struct ring_buffer_per_cpu *
+rb_start_write(struct trace_buffer *buffer)
+{
+	struct ring_buffer_per_cpu *cpu_buffer;
+	int cpu;
+
+	/* If we are tracing schedule, we don't want to recurse */
+	preempt_disable_notrace();
+
+	if (unlikely(atomic_read(&buffer->record_disabled)))
+		goto out;
+
+	cpu = raw_smp_processor_id();
+
+	if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
+		goto out;
+
+	cpu_buffer = buffer->buffers[cpu];
+
+	if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
+		goto out;
+
+	if (unlikely(trace_recursive_lock(cpu_buffer)))
+		goto out;
+
+	return cpu_buffer;
+
+out:
+	preempt_enable_notrace();
+
+	return NULL;
+}
+
+static __always_inline void rb_end_write(struct ring_buffer_per_cpu *cpu_buffer)
+{
+	trace_recursive_unlock(cpu_buffer);
+	preempt_enable_notrace();
+}
+
 /* The recursive locking above uses 5 bits */
 #define NESTED_BITS 5
 
@@ -4563,9 +4602,7 @@ int ring_buffer_unlock_commit(struct trace_buffer *buffer)
 
 	rb_wakeups(buffer, cpu_buffer);
 
-	trace_recursive_unlock(cpu_buffer);
-
-	preempt_enable_notrace();
+	rb_end_write(cpu_buffer);
 
 	return 0;
 }
@@ -5027,38 +5064,16 @@ ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct ring_buffer_event *event;
-	int cpu;
 
-	/* If we are tracing schedule, we don't want to recurse */
-	preempt_disable_notrace();
-
-	if (unlikely(atomic_read(&buffer->record_disabled)))
-		goto out;
-
-	cpu = raw_smp_processor_id();
-
-	if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
-		goto out;
-
-	cpu_buffer = buffer->buffers[cpu];
-
-	if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
-		goto out;
-
-	if (unlikely(trace_recursive_lock(cpu_buffer)))
-		goto out;
+	cpu_buffer = rb_start_write(buffer);
+	if (!cpu_buffer)
+		return NULL;
 
 	event = rb_reserve_next_event(buffer, cpu_buffer, length);
 	if (!event)
-		goto out_unlock;
+		rb_end_write(cpu_buffer);
 
 	return event;
-
- out_unlock:
-	trace_recursive_unlock(cpu_buffer);
- out:
-	preempt_enable_notrace();
-	return NULL;
 }
 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
 
@@ -5143,11 +5158,7 @@ void ring_buffer_discard_commit(struct trace_buffer *buffer,
 	rb_decrement_entry(cpu_buffer, event);
 	rb_try_to_discard(cpu_buffer, event);
 	rb_end_commit(cpu_buffer);
-
-	trace_recursive_unlock(cpu_buffer);
-
-	preempt_enable_notrace();
-
+	rb_end_write(cpu_buffer);
 }
 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
 
@@ -5170,31 +5181,16 @@ int ring_buffer_write(struct trace_buffer *buffer,
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct ring_buffer_event *event;
-	void *body;
 	int ret = -EBUSY;
-	int cpu;
+	void *body;
 
-	guard(preempt_notrace)();
-
-	if (atomic_read(&buffer->record_disabled))
-		return -EBUSY;
-
-	cpu = raw_smp_processor_id();
-
-	if (!cpumask_test_cpu(cpu, buffer->cpumask))
-		return -EBUSY;
-
-	cpu_buffer = buffer->buffers[cpu];
-
-	if (atomic_read(&cpu_buffer->record_disabled))
-		return -EBUSY;
-
-	if (unlikely(trace_recursive_lock(cpu_buffer)))
+	cpu_buffer = rb_start_write(buffer);
+	if (!cpu_buffer)
 		return -EBUSY;
 
 	event = rb_reserve_next_event(buffer, cpu_buffer, length);
 	if (!event)
-		goto out_unlock;
+		goto out;
 
 	body = rb_event_data(event);
 
@@ -5206,8 +5202,8 @@ int ring_buffer_write(struct trace_buffer *buffer,
 
 	ret = 0;
 
- out_unlock:
-	trace_recursive_unlock(cpu_buffer);
+out:
+	rb_end_write(cpu_buffer);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(ring_buffer_write);
-- 
2.56.0.567.gdb80ae8cd5-goog