tracing: Generalize per-element hist trigger data

Up until now, hist triggers only needed per-element support for saving
'comm' data, which was saved directly as a private data pointer.

In anticipation of the need to save other data besides 'comm', add a
new hist_elt_data struct for the purpose, and switch the current
'comm'-related code over to that.

Link: http://lkml.kernel.org/r/4502c338c965ddf5fc19fb1ec4764391e001ed4b.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4c3c7d784bfd771df023445150b3be9fa3a2f018..f072ed3122c802a67cb3259c39747122ba21fdfc 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -289,6 +289,10 @@ static struct hist_field *find_var(struct hist_trigger_data *hist_data,
        return NULL;
 }
 
+struct hist_elt_data {
+       char *comm;
+};
+
 static const char *hist_field_name(struct hist_field *field,
                                   unsigned int level)
 {
@@ -503,45 +507,61 @@ static inline void save_comm(char *comm, struct task_struct *task)
        memcpy(comm, task->comm, TASK_COMM_LEN);
 }
 
-static void hist_trigger_elt_comm_free(struct tracing_map_elt *elt)
+static void hist_elt_data_free(struct hist_elt_data *elt_data)
+{
+       kfree(elt_data->comm);
+       kfree(elt_data);
+}
+
+static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
 {
-       kfree((char *)elt->private_data);
+       struct hist_elt_data *elt_data = elt->private_data;
+
+       hist_elt_data_free(elt_data);
 }
 
-static int hist_trigger_elt_comm_alloc(struct tracing_map_elt *elt)
+static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
 {
        struct hist_trigger_data *hist_data = elt->map->private_data;
+       unsigned int size = TASK_COMM_LEN;
+       struct hist_elt_data *elt_data;
        struct hist_field *key_field;
        unsigned int i;
 
+       elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
+       if (!elt_data)
+               return -ENOMEM;
+
        for_each_hist_key_field(i, hist_data) {
                key_field = hist_data->fields[i];
 
                if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
-                       unsigned int size = TASK_COMM_LEN + 1;
-
-                       elt->private_data = kzalloc(size, GFP_KERNEL);
-                       if (!elt->private_data)
+                       elt_data->comm = kzalloc(size, GFP_KERNEL);
+                       if (!elt_data->comm) {
+                               kfree(elt_data);
                                return -ENOMEM;
+                       }
                        break;
                }
        }
 
+       elt->private_data = elt_data;
+
        return 0;
 }
 
-static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
+static void hist_trigger_elt_data_init(struct tracing_map_elt *elt)
 {
-       char *comm = elt->private_data;
+       struct hist_elt_data *elt_data = elt->private_data;
 
-       if (comm)
-               save_comm(comm, current);
+       if (elt_data->comm)
+               save_comm(elt_data->comm, current);
 }
 
-static const struct tracing_map_ops hist_trigger_elt_comm_ops = {
-       .elt_alloc      = hist_trigger_elt_comm_alloc,
-       .elt_free       = hist_trigger_elt_comm_free,
-       .elt_init       = hist_trigger_elt_comm_init,
+static const struct tracing_map_ops hist_trigger_elt_data_ops = {
+       .elt_alloc      = hist_trigger_elt_data_alloc,
+       .elt_free       = hist_trigger_elt_data_free,
+       .elt_init       = hist_trigger_elt_data_init,
 };
 
 static const char *get_hist_field_flags(struct hist_field *hist_field)
@@ -1484,21 +1504,6 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
        return 0;
 }
 
-static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
-{
-       struct hist_field *key_field;
-       unsigned int i;
-
-       for_each_hist_key_field(i, hist_data) {
-               key_field = hist_data->fields[i];
-
-               if (key_field->flags & HIST_FIELD_FL_EXECNAME)
-                       return true;
-       }
-
-       return false;
-}
-
 static struct hist_trigger_data *
 create_hist_data(unsigned int map_bits,
                 struct hist_trigger_attrs *attrs,
@@ -1524,8 +1529,7 @@ create_hist_data(unsigned int map_bits,
        if (ret)
                goto free;
 
-       if (need_tracing_map_ops(hist_data))
-               map_ops = &hist_trigger_elt_comm_ops;
+       map_ops = &hist_trigger_elt_data_ops;
 
        hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
                                            map_ops, hist_data);
@@ -1713,7 +1717,13 @@ hist_trigger_entry_print(struct seq_file *m,
                        seq_printf(m, "%s: [%llx] %-55s", field_name,
                                   uval, str);
                } else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
-                       char *comm = elt->private_data;
+                       struct hist_elt_data *elt_data = elt->private_data;
+                       char *comm;
+
+                       if (WARN_ON_ONCE(!elt_data))
+                               return;
+
+                       comm = elt_data->comm;
 
                        uval = *(u64 *)(key + key_field->offset);
                        seq_printf(m, "%s: %-16s[%10llu]", field_name,