tracing: Add a resize function to make one buffer equivalent to another buffer

Trace buffer size is now per-cpu, so that there are the following two
patterns in resizing of buffers.

  (1) resize per-cpu buffers to same given size
  (2) resize per-cpu buffers to another trace_array's buffer size
      for each CPU (such as preparing the max_tr which is equivalent
      to the global_trace's size)

__tracing_resize_ring_buffer() can be used for (1), and had
implemented (2) inside it for resetting the global_trace to the
original size.

(2) was also implemented in another place. So this patch assembles
them in a new function - resize_buffer_duplicate_size().

Link: http://lkml.kernel.org/r/20121017025616.2627.91226.stgit@falsita
Signed-off-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b69cc380322dbfe17983e582a9537d6e53e1ce7b..64ad9bc4275be0ddb837e72cff6632c7eaf40d97 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3034,6 +3034,31 @@ static void set_buffer_entries(struct trace_array *tr, unsigned long val)
                tr->data[cpu]->entries = val;
 }
 
+/* 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)
+{
+       int cpu, ret = 0;
+
+       if (cpu_id == RING_BUFFER_ALL_CPUS) {
+               for_each_tracing_cpu(cpu) {
+                       ret = ring_buffer_resize(tr->buffer,
+                                       size_tr->data[cpu]->entries, cpu);
+                       if (ret < 0)
+                               break;
+                       tr->data[cpu]->entries = size_tr->data[cpu]->entries;
+               }
+       } else {
+               ret = ring_buffer_resize(tr->buffer,
+                                       size_tr->data[cpu_id]->entries, cpu_id);
+               if (ret == 0)
+                       tr->data[cpu_id]->entries =
+                               size_tr->data[cpu_id]->entries;
+       }
+
+       return ret;
+}
+
 static int __tracing_resize_ring_buffer(unsigned long size, int cpu)
 {
        int ret;
@@ -3058,23 +3083,8 @@ static int __tracing_resize_ring_buffer(unsigned long size, int cpu)
 
        ret = ring_buffer_resize(max_tr.buffer, size, cpu);
        if (ret < 0) {
-               int r = 0;
-
-               if (cpu == RING_BUFFER_ALL_CPUS) {
-                       int i;
-                       for_each_tracing_cpu(i) {
-                               r = ring_buffer_resize(global_trace.buffer,
-                                               global_trace.data[i]->entries,
-                                               i);
-                               if (r < 0)
-                                       break;
-                       }
-               } else {
-                       r = ring_buffer_resize(global_trace.buffer,
-                                               global_trace.data[cpu]->entries,
-                                               cpu);
-               }
-
+               int r = resize_buffer_duplicate_size(&global_trace,
+                                                    &global_trace, cpu);
                if (r < 0) {
                        /*
                         * AARGH! We are left with different
@@ -3212,17 +3222,11 @@ static int tracing_set_tracer(const char *buf)
 
        topts = create_trace_option_files(t);
        if (t->use_max_tr) {
-               int cpu;
                /* we need to make per cpu buffer sizes equivalent */
-               for_each_tracing_cpu(cpu) {
-                       ret = ring_buffer_resize(max_tr.buffer,
-                                               global_trace.data[cpu]->entries,
-                                               cpu);
-                       if (ret < 0)
-                               goto out;
-                       max_tr.data[cpu]->entries =
-                                       global_trace.data[cpu]->entries;
-               }
+               ret = resize_buffer_duplicate_size(&max_tr, &global_trace,
+                                                  RING_BUFFER_ALL_CPUS);
+               if (ret < 0)
+                       goto out;
        }
 
        if (t->init) {