tracing/stat: do some cleanups

- remove duplicate code in stat_seq_init()
- update comments to reflect the change from stat list to stat rbtree

[ Impact: clean up ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 21 insertions, 33 deletions

diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 8030ec98dbad..17f20ebdad2a 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -93,10 +93,15 @@ static void destroy_session(struct stat_session *session)
 
 typedef int (*cmp_stat_t)(void *, void *);
 
-static void
-insert_stat(struct rb_root *root, struct stat_node *data, cmp_stat_t cmp)
+static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
 {
         struct rb_node **new = &(root->rb_node), *parent = NULL;
+        struct stat_node *data;
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+        data->stat = stat;
 
         /*
          * Figure out where to put new node
@@ -118,12 +123,13 @@ insert_stat(struct rb_root *root, struct stat_node *data, cmp_stat_t cmp)
 
         rb_link_node(&data->node, parent, new);
         rb_insert_color(&data->node, root);
+        return 0;
 }
 
 /*
  * For tracers that don't provide a stat_cmp callback.
- * This one will force an immediate insertion on tail of
- * the list.
+ * This one will force an insertion as right-most node
+ * in the rbtree.
  */
 static int dummy_cmp(void *p1, void *p2)
 {
@@ -131,15 +137,14 @@ static int dummy_cmp(void *p1, void *p2)
 }
 
 /*
- * Initialize the stat list at each trace_stat file opening.
+ * Initialize the stat rbtree at each trace_stat file opening.
  * All of these copies and sorting are required on all opening
  * since the stats could have changed between two file sessions.
  */
 static int stat_seq_init(struct stat_session *session)
 {
         struct tracer_stat *ts = session->ts;
-        struct stat_node *new_entry;
-        struct rb_root *root;
+        struct rb_root *root = &session->stat_root;
         void *stat;
         int ret = 0;
         int i;
@@ -154,23 +159,12 @@ static int stat_seq_init(struct stat_session *session)
         if (!stat)
                 goto exit;
 
-        /*
-         * The first entry. Actually this is the second, but the first
-         * one (the stat_list head) is pointless.
-         */
-        new_entry = kzalloc(sizeof(*new_entry), GFP_KERNEL);
-        if (!new_entry) {
-                ret = -ENOMEM;
+        ret = insert_stat(root, stat, ts->stat_cmp);
+        if (ret)
                 goto exit;
-        }
-        root = &session->stat_root;
-        insert_stat(root, new_entry, dummy_cmp);
-
-        new_entry->stat = stat;
 
         /*
-         * Iterate over the tracer stat entries and store them in a sorted
-         * list.
+         * Iterate over the tracer stat entries and store them in an rbtree.
          */
         for (i = 1; ; i++) {
                 stat = ts->stat_next(stat, i);
@@ -179,22 +173,16 @@ static int stat_seq_init(struct stat_session *session)
                 if (!stat)
                         break;
 
-                new_entry = kzalloc(sizeof(*new_entry), GFP_KERNEL);
-                if (!new_entry) {
-                        ret = -ENOMEM;
-                        goto exit_free_list;
-                }
-
-                new_entry->stat = stat;
-
-                insert_stat(root, new_entry, ts->stat_cmp);
+                ret = insert_stat(root, stat, ts->stat_cmp);
+                if (ret)
+                        goto exit_free_rbtree;
         }
 
 exit:
         mutex_unlock(&session->stat_mutex);
         return ret;
 
-exit_free_list:
+exit_free_rbtree:
         reset_stat_session(session);
         mutex_unlock(&session->stat_mutex);
         return ret;
@@ -207,7 +195,7 @@ static void *stat_seq_start(struct seq_file *s, loff_t *pos)
         struct rb_node *node;
         int i;
 
-        /* Prevent from tracer switch or stat_list modification */
+        /* Prevent from tracer switch or rbtree modification */
         mutex_lock(&session->stat_mutex);
 
         /* If we are in the beginning of the file, print the headers */
@@ -280,7 +268,7 @@ static int tracing_stat_open(struct inode *inode, struct file *file)
 }
 
 /*
- * Avoid consuming memory with our now useless list.
+ * Avoid consuming memory with our now useless rbtree.
  */
 static int tracing_stat_release(struct inode *i, struct file *f)
 {