[ltt-dev] [PATCH] lttng: remove ltt root directory if it's no needed

[guijianfeng@cn.fujitsu.com (Gui Jianfeng)]

We have to cleanup the lttng's root directory of debugfs if 
there is nobody uses it any more.

This patch is based on 2.6.29-rc3-lttng-0.92.

Signed-off-by: Gui Jianfeng <guijianfeng at cn.fujitsu.com>
---
 include/linux/ltt-core.h  |    1 +
 ltt/ltt-core.c            |    7 +++++++
 ltt/ltt-trace-control.c   |   11 +++++++++++
 ltt/ltt-userspace-event.c |   10 ++++++++++
 4 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/include/linux/ltt-core.h b/include/linux/ltt-core.h
index bc244c6..e43fc52 100644
--- a/include/linux/ltt-core.h
+++ b/include/linux/ltt-core.h
@@ -30,6 +30,7 @@ extern struct ltt_traces ltt_traces;
 /*
  * get dentry of ltt's root dir
  */
+void reset_ltt_root(void);
 struct dentry *get_ltt_root(void);
 
 /* Keep track of trap nesting inside LTT */
diff --git a/ltt/ltt-core.c b/ltt/ltt-core.c
index 18db91d..26c04b5 100644
--- a/ltt/ltt-core.c
+++ b/ltt/ltt-core.c
@@ -23,6 +23,13 @@ static DEFINE_MUTEX(ltt_traces_mutex);
 
 /* dentry of ltt's root dir */
 static struct dentry *ltt_root_dentry;
+
+void reset_ltt_root(void)
+{
+	ltt_root_dentry = NULL;
+}
+EXPORT_SYMBOL_GPL(reset_ltt_root);
+
 struct dentry *get_ltt_root(void)
 {
 	if (!ltt_root_dentry) {
diff --git a/ltt/ltt-trace-control.c b/ltt/ltt-trace-control.c
index 16502a2..21416b1 100644
--- a/ltt/ltt-trace-control.c
+++ b/ltt/ltt-trace-control.c
@@ -740,6 +740,10 @@ err_create_destroy_trace_file:
 err_create_setup_trace_file:
 	debugfs_remove(ltt_control_dir);
 err_create_control_dir:
+	if (list_empty(&ltt_root_dentry->d_subdirs)) {
+		debugfs_remove(ltt_root_dentry);
+		reset_ltt_root();
+	}
 err_no_root:
 	return err;
 }
@@ -747,6 +751,9 @@ err_no_root:
 static void __exit ltt_trace_control_exit(void)
 {
 	struct dentry *trace_dir;
+	struct dentry *ltt_root_dentry;
+
+	ltt_root_dentry = get_ltt_root();
 
 	/* destory all traces */
 	list_for_each_entry(trace_dir, &ltt_control_dir->d_subdirs,
@@ -759,6 +766,10 @@ static void __exit ltt_trace_control_exit(void)
 	debugfs_remove(ltt_setup_trace_file);
 	debugfs_remove(ltt_destroy_trace_file);
 	debugfs_remove_recursive(ltt_control_dir);
+	if (list_empty(&ltt_root_dentry->d_subdirs)) {
+		debugfs_remove(ltt_root_dentry);
+		reset_ltt_root();
+	}
 }
 
 module_init(ltt_trace_control_init);
diff --git a/ltt/ltt-userspace-event.c b/ltt/ltt-userspace-event.c
index 385bd3b..ef4fbb2 100644
--- a/ltt/ltt-userspace-event.c
+++ b/ltt/ltt-userspace-event.c
@@ -117,7 +117,17 @@ err_no_root:
 
 static void __exit ltt_userspace_exit(void)
 {
+	struct dentry *ltt_root_dentry;
+
+	ltt_root_dentry = get_ltt_root();
+
 	debugfs_remove(ltt_event_file);
+	if (ltt_root_dentry) {
+		if (list_empty(&ltt_root_dentry->d_subdirs)) {
+			debugfs_remove(ltt_root_dentry);
+			reset_ltt_root();
+		}
+	}
 }
 
 module_init(ltt_userspace_init);
-- 
1.5.4.rc3