[ltt-dev] [PATCH v4 3/4] Add get_ltt_root() to get dentry of ltt's root dir

[Zhaolei]

get_ltt_root() is necessary for ltt-trace-control to create subdirs in ltt's
debugfs dir.

Signed-off-by: Zhao Lei <zhaolei at cn.fujitsu.com>
---
 include/linux/ltt-core.h |    8 ++++++++
 ltt/ltt-core.c           |   14 ++++++++++++++
 ltt/ltt-relay.c          |    8 +-------
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/ltt-core.h b/include/linux/ltt-core.h
index 7e5ee8b..076c3ed 100644
--- a/include/linux/ltt-core.h
+++ b/include/linux/ltt-core.h
@@ -10,6 +10,9 @@
 #include <linux/list.h>
 #include <linux/percpu.h>
 
+/* ltt's root dir in debugfs */
+#define LTT_ROOT        "ltt"
+
 /*
  * All modifications of ltt_traces must be done by ltt-tracer.c, while holding
  * the semaphore. Only reading of this information can be done elsewhere, with
@@ -24,6 +27,11 @@ struct ltt_traces {
 
 extern struct ltt_traces ltt_traces;
 
+/*
+ * get dentry of ltt's root dir
+ */
+struct dentry *get_ltt_root(void);
+
 /* Keep track of trap nesting inside LTT */
 DECLARE_PER_CPU(unsigned int, ltt_nesting);
 
diff --git a/ltt/ltt-core.c b/ltt/ltt-core.c
index aaad358..0ed1d06 100644
--- a/ltt/ltt-core.c
+++ b/ltt/ltt-core.c
@@ -9,6 +9,7 @@
 #include <linux/ltt-core.h>
 #include <linux/percpu.h>
 #include <linux/module.h>
+#include <linux/debugfs.h>
 
 /* Traces structures */
 struct ltt_traces ltt_traces = {
@@ -20,6 +21,19 @@ EXPORT_SYMBOL(ltt_traces);
 /* Traces list writer locking */
 static DEFINE_MUTEX(ltt_traces_mutex);
 
+/* dentry of ltt's root dir */
+static struct dentry *ltt_root_dentry;
+struct dentry *get_ltt_root(void)
+{
+	if (!ltt_root_dentry) {
+		ltt_root_dentry = debugfs_create_dir(LTT_ROOT, NULL);
+		if (!ltt_root_dentry)
+			printk(KERN_ERR "LTT : ctrate ltt root dir failed\n");
+	}
+	return ltt_root_dentry;
+}
+EXPORT_SYMBOL_GPL(get_ltt_root);
+
 void ltt_lock_traces(void)
 {
 	mutex_lock(&ltt_traces_mutex);
diff --git a/ltt/ltt-relay.c b/ltt/ltt-relay.c
index c6e1d52..535bd2e 100644
--- a/ltt/ltt-relay.c
+++ b/ltt/ltt-relay.c
@@ -131,7 +131,6 @@ static inline int last_tsc_overflow(struct ltt_channel_buf_struct *ltt_buf,
 }
 #endif
 
-static struct dentry *ltt_root_dentry;
 static struct file_operations ltt_file_operations;
 
 /*
@@ -803,7 +802,7 @@ end:
 static int ltt_relay_create_dirs(struct ltt_trace_struct *new_trace)
 {
 	new_trace->dentry.trace_root = debugfs_create_dir(new_trace->trace_name,
-			ltt_root_dentry);
+			get_ltt_root());
 	if (new_trace->dentry.trace_root == NULL) {
 		printk(KERN_ERR "LTT : Trace directory name %s already taken\n",
 				new_trace->trace_name);
@@ -1614,9 +1613,6 @@ static struct ltt_transport ltt_relay_transport = {
 static int __init ltt_relay_init(void)
 {
 	printk(KERN_INFO "LTT : ltt-relay init\n");
-	ltt_root_dentry = debugfs_create_dir(LTT_RELAY_ROOT, NULL);
-	if (ltt_root_dentry == NULL)
-		return -EEXIST;
 
 	ltt_file_operations = ltt_relay_file_operations;
 	ltt_file_operations.owner = THIS_MODULE;
@@ -1637,8 +1633,6 @@ static void __exit ltt_relay_exit(void)
 	printk(KERN_INFO "LTT : ltt-relay exit\n");
 
 	ltt_transport_unregister(&ltt_relay_transport);
-
-	debugfs_remove(ltt_root_dentry);
 }
 
 module_init(ltt_relay_init);
-- 
1.5.5.3