Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux...

[karo-tx-linux.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a0c6af34d50063b31f6bd1fd1fc1de8b299d10ce..72fcd3069a909064529f1eb730e4985d16cef006 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -896,10 +896,13 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
                mutex_unlock(&cgroup_mutex);
 
                /*
-                * Drop the active superblock reference that we took when we
-                * created the cgroup
+                * We want to drop the active superblock reference from the
+                * cgroup creation after all the dentry refs are gone -
+                * kill_sb gets mighty unhappy otherwise.  Mark
+                * dentry->d_fsdata with cgroup_diput() to tell
+                * cgroup_d_release() to call deactivate_super().
                 */
-               deactivate_super(cgrp->root->sb);
+               dentry->d_fsdata = cgroup_diput;
 
                /*
                 * if we're getting rid of the cgroup, refcount should ensure
@@ -925,6 +928,13 @@ static int cgroup_delete(const struct dentry *d)
        return 1;
 }
 
+static void cgroup_d_release(struct dentry *dentry)
+{
+       /* did cgroup_diput() tell me to deactivate super? */
+       if (dentry->d_fsdata == cgroup_diput)
+               deactivate_super(dentry->d_sb);
+}
+
 static void remove_dir(struct dentry *d)
 {
        struct dentry *parent = dget(d->d_parent);
@@ -1532,6 +1542,7 @@ static int cgroup_get_rootdir(struct super_block *sb)
        static const struct dentry_operations cgroup_dops = {
                .d_iput = cgroup_diput,
                .d_delete = cgroup_delete,
+               .d_release = cgroup_d_release,
        };
 
        struct inode *inode =
@@ -5132,7 +5143,7 @@ EXPORT_SYMBOL_GPL(css_depth);
  * @root: the css supporsed to be an ancestor of the child.
  *
  * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
- * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
+ * this function reads css->id, the caller must hold rcu_read_lock().
  * But, considering usual usage, the csses should be valid objects after test.
  * Assuming that the caller will do some action to the child if this returns
  * returns true, the caller must take "child";s reference count.
@@ -5144,18 +5155,18 @@ bool css_is_ancestor(struct cgroup_subsys_state *child,
 {
        struct css_id *child_id;
        struct css_id *root_id;
-       bool ret = true;
 
-       rcu_read_lock();
        child_id  = rcu_dereference(child->id);
+       if (!child_id)
+               return false;
        root_id = rcu_dereference(root->id);
-       if (!child_id
-           || !root_id
-           || (child_id->depth < root_id->depth)
-           || (child_id->stack[root_id->depth] != root_id->id))
-               ret = false;
-       rcu_read_unlock();
-       return ret;
+       if (!root_id)
+               return false;
+       if (child_id->depth < root_id->depth)
+               return false;
+       if (child_id->stack[root_id->depth] != root_id->id)
+               return false;
+       return true;
 }
 
 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)