[RFC Aufs2 #2 22/28] aufs branch for loopback block device

["J. R. Okajima" <hooanon05@yahoo.co.jp>]

initial commit
support and test loopback block device as a branch

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
---
 fs/aufs/loop.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/aufs/loop.h |   41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 0 deletions(-)
 create mode 100644 fs/aufs/loop.c
 create mode 100644 fs/aufs/loop.h

diff --git a/fs/aufs/loop.c b/fs/aufs/loop.c
new file mode 100644
index 0000000..84a940f
--- /dev/null
+++ b/fs/aufs/loop.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2005-2009 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.
+ */
+
+/*
+ * 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_d1,
+			     struct dentry *h_d2)
+{
+	struct inode *h_inode;
+	struct loop_device *l;
+
+	h_inode = h_d1->d_inode;
+	if (MAJOR(h_inode->i_sb->s_dev) != LOOP_MAJOR)
+		return 0;
+
+	l = h_inode->i_sb->s_bdev->bd_disk->private_data;
+	h_d1 = l->lo_backing_file->f_dentry;
+	/* h_d1 can be local NFS. in this case aufs cannot detect the loop */
+	if (unlikely(h_d1->d_sb == sb))
+		return 1;
+	return !!au_test_subdir(h_d1, h_d2);
+}
+
+/* true if a kernel thread named 'loop[0-9].*' accesses a file */
+int au_test_loopback_kthread(void)
+{
+	const char c = current->comm[4];
+
+	return current->mm == NULL
+	       && '0' <= c && c <= '9'
+	       && strncmp(current->comm, "loop", 4) == 0;
+}
diff --git a/fs/aufs/loop.h b/fs/aufs/loop.h
new file mode 100644
index 0000000..1c0ee40
--- /dev/null
+++ b/fs/aufs/loop.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2005-2009 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.
+ */
+
+/*
+ * support for loopback mount as a branch
+ */
+
+#ifndef __AUFS_LOOP_H__
+#define __AUFS_LOOP_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+
+#ifdef CONFIG_AUFS_BDEV_LOOP
+/* loop.c */
+int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_d1,
+			     struct dentry *h_d2);
+int au_test_loopback_kthread(void);
+#else
+static inline
+int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_d1,
+			     struct dentry *h_d2)
+{
+	return 0;
+}
+
+static inline int au_test_loopback_kthread(void)
+{
+	return 0;
+}
+#endif /* BLK_DEV_LOOP */
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_LOOP_H__ */
-- 
1.6.1.284.g5dc13