aufs: add files

[pandora-kernel.git] / fs / aufs / loop.c

diff --git a/fs/aufs/loop.c b/fs/aufs/loop.c
new file mode 100644 (file)
index 0000000..1fbe0c4
--- /dev/null
+++ b/fs/aufs/loop.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2005-2011 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+/*
+ * support for loopback block device as a branch
+ */
+
+#include <linux/loop.h>
+#include "aufs.h"
+
+/*
+ * test if two lower dentries have overlapping branches.
+ */
+int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_adding)
+{
+       struct super_block *h_sb;
+       struct loop_device *l;
+
+       h_sb = h_adding->d_sb;
+       if (MAJOR(h_sb->s_dev) != LOOP_MAJOR)
+               return 0;
+
+       l = h_sb->s_bdev->bd_disk->private_data;
+       h_adding = l->lo_backing_file->f_dentry;
+       /*
+        * h_adding can be local NFS.
+        * in this case aufs cannot detect the loop.
+        */
+       if (unlikely(h_adding->d_sb == sb))
+               return 1;
+       return !!au_test_subdir(h_adding, sb->s_root);
+}
+
+/* true if a kernel thread named 'loop[0-9].*' accesses a file */
+int au_test_loopback_kthread(void)
+{
+       int ret;
+       struct task_struct *tsk = current;
+
+       ret = 0;
+       if (tsk->flags & PF_KTHREAD) {
+               const char c = tsk->comm[4];
+               ret = ('0' <= c && c <= '9'
+                      && !strncmp(tsk->comm, "loop", 4));
+       }
+
+       return ret;
+}