vfs: Add a function to lazily unmount all mounts from any dentry.

[android-x86/kernel.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index 88fc3f4..00e5b1e 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1468,6 +1468,37 @@ static int do_umount(struct mount *mnt, int flags)
        return retval;
 }
 
+/*
+ * __detach_mounts - lazily unmount all mounts on the specified dentry
+ *
+ * During unlink, rmdir, and d_drop it is possible to loose the path
+ * to an existing mountpoint, and wind up leaking the mount.
+ * detach_mounts allows lazily unmounting those mounts instead of
+ * leaking them.
+ *
+ * The caller may hold dentry->d_inode->i_mutex.
+ */
+void __detach_mounts(struct dentry *dentry)
+{
+       struct mountpoint *mp;
+       struct mount *mnt;
+
+       namespace_lock();
+       mp = lookup_mountpoint(dentry);
+       if (!mp)
+               goto out_unlock;
+
+       lock_mount_hash();
+       while (!hlist_empty(&mp->m_list)) {
+               mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
+               umount_tree(mnt, 2);
+       }
+       unlock_mount_hash();
+       put_mountpoint(mp);
+out_unlock:
+       namespace_unlock();
+}
+
 /* 
  * Is the caller allowed to modify his namespace?
  */