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Subject[PATCH 2/3] tracing/stat: simplify rbtree freeing code
When closing a trace_stat file, we destroy the rbtree constructed during
file open, but there is memory leak that the root node is not freed:

static struct rb_node *release_next(struct rb_node *node)
{
...
else {
if (!parent) <-- here we leak @node
return NULL;
...
}
This patch keeps removing root node until the tree is empty. We regress
from O(n) to O(nlogn), but since both open() and read() are O(nlogn) and
it's a slow path, this change won't affect scalibility.

[ Impact: fix memory leak when closing a trace_stat file ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/trace/trace_stat.c | 39 +++++----------------------------------
1 files changed, 5 insertions(+), 34 deletions(-)
diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 6efbcb4..ed18701 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -42,47 +42,18 @@ static DEFINE_MUTEX(all_stat_sessions_mutex);
/* The root directory for all stat files */
static struct dentry *stat_dir;

-/*
- * Iterate through the rbtree using a post order traversal path
- * to release the next node.
- * It won't necessary release one at each iteration
- * but it will at least advance closer to the next one
- * to be released.
- */
-static struct rb_node *release_next(struct rb_node *node)
+static void reset_stat_session(struct stat_session *session)
{
struct stat_node *snode;
- struct rb_node *parent = rb_parent(node);
-
- if (node->rb_left)
- return node->rb_left;
- else if (node->rb_right)
- return node->rb_right;
- else {
- if (!parent)
- return NULL;
- if (parent->rb_left == node)
- parent->rb_left = NULL;
- else
- parent->rb_right = NULL;
+ struct rb_root *sroot = &session->stat_root;

- snode = container_of(node, struct stat_node, node);
+ while (!RB_EMPTY_ROOT(sroot)) {
+ snode = rb_entry(sroot->rb_node, struct stat_node, node);
+ rb_erase(&snode->node, sroot);
kfree(snode);
-
- return parent;
}
}

-static void reset_stat_session(struct stat_session *session)
-{
- struct rb_node *node = session->stat_root.rb_node;
-
- while (node)
- node = release_next(node);
-
- session->stat_root = RB_ROOT;
-}
-
static void destroy_session(struct stat_session *session)
{
debugfs_remove(session->file);
--
1.5.4.rc3


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