ASoC: sglt5000: Fix SGTL5000_PLL_FRAC_DIV_MASK

[firefly-linux-kernel-4.4.55.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a7c9e6ddb9797a886e96bbff7c75fb8ed9670c68..c6e77ef2a0a65212848aa19bafd6819b760eb766 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3726,6 +3726,23 @@ static int cgroup_write_notify_on_release(struct cgroup *cgrp,
        return 0;
 }
 
+/*
+ * When dput() is called asynchronously, if umount has been done and
+ * then deactivate_super() in cgroup_free_fn() kills the superblock,
+ * there's a small window that vfs will see the root dentry with non-zero
+ * refcnt and trigger BUG().
+ *
+ * That's why we hold a reference before dput() and drop it right after.
+ */
+static void cgroup_dput(struct cgroup *cgrp)
+{
+       struct super_block *sb = cgrp->root->sb;
+
+       atomic_inc(&sb->s_active);
+       dput(cgrp->dentry);
+       deactivate_super(sb);
+}
+
 /*
  * Unregister event and free resources.
  *
@@ -3746,7 +3763,7 @@ static void cgroup_event_remove(struct work_struct *work)
 
        eventfd_ctx_put(event->eventfd);
        kfree(event);
-       dput(cgrp->dentry);
+       cgroup_dput(cgrp);
 }
 
 /*
@@ -4031,12 +4048,8 @@ static void css_dput_fn(struct work_struct *work)
 {
        struct cgroup_subsys_state *css =
                container_of(work, struct cgroup_subsys_state, dput_work);
-       struct dentry *dentry = css->cgroup->dentry;
-       struct super_block *sb = dentry->d_sb;
 
-       atomic_inc(&sb->s_active);
-       dput(dentry);
-       deactivate_super(sb);
+       cgroup_dput(css->cgroup);
 }
 
 static void init_cgroup_css(struct cgroup_subsys_state *css,