diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 1384823a160..bc1f3b9d811 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -3,6 +3,7 @@
 #
 
 fscache-y := \
+	fsdef.o \
 	main.o
 
 fscache-$(CONFIG_PROC_FS) += proc.o
diff --git a/fs/fscache/fsdef.c b/fs/fscache/fsdef.c
new file mode 100644
index 00000000000..f5b4baee735
--- /dev/null
+++ b/fs/fscache/fsdef.c
@@ -0,0 +1,144 @@
+/* Filesystem index definition
+ *
+ * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program 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.
+ */
+
+#define FSCACHE_DEBUG_LEVEL CACHE
+#include <linux/module.h>
+#include "internal.h"
+
+static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
+					    void *buffer, uint16_t bufmax);
+
+static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
+					    void *buffer, uint16_t bufmax);
+
+static
+enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
+						    const void *data,
+						    uint16_t datalen);
+
+/*
+ * The root index is owned by FS-Cache itself.
+ *
+ * When a netfs requests caching facilities, FS-Cache will, if one doesn't
+ * already exist, create an entry in the root index with the key being the name
+ * of the netfs ("AFS" for example), and the auxiliary data holding the index
+ * structure version supplied by the netfs:
+ *
+ *				     FSDEF
+ *				       |
+ *				 +-----------+
+ *				 |           |
+ *				NFS         AFS
+ *			       [v=1]       [v=1]
+ *
+ * If an entry with the appropriate name does already exist, the version is
+ * compared.  If the version is different, the entire subtree from that entry
+ * will be discarded and a new entry created.
+ *
+ * The new entry will be an index, and a cookie referring to it will be passed
+ * to the netfs.  This is then the root handle by which the netfs accesses the
+ * cache.  It can create whatever objects it likes in that index, including
+ * further indices.
+ */
+static struct fscache_cookie_def fscache_fsdef_index_def = {
+	.name		= ".FS-Cache",
+	.type		= FSCACHE_COOKIE_TYPE_INDEX,
+};
+
+struct fscache_cookie fscache_fsdef_index = {
+	.usage		= ATOMIC_INIT(1),
+	.lock		= __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
+	.backing_objects = HLIST_HEAD_INIT,
+	.def		= &fscache_fsdef_index_def,
+};
+EXPORT_SYMBOL(fscache_fsdef_index);
+
+/*
+ * Definition of an entry in the root index.  Each entry is an index, keyed to
+ * a specific netfs and only applicable to a particular version of the index
+ * structure used by that netfs.
+ */
+struct fscache_cookie_def fscache_fsdef_netfs_def = {
+	.name		= "FSDEF.netfs",
+	.type		= FSCACHE_COOKIE_TYPE_INDEX,
+	.get_key	= fscache_fsdef_netfs_get_key,
+	.get_aux	= fscache_fsdef_netfs_get_aux,
+	.check_aux	= fscache_fsdef_netfs_check_aux,
+};
+
+/*
+ * get the key data for an FSDEF index record - this is the name of the netfs
+ * for which this entry is created
+ */
+static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
+					    void *buffer, uint16_t bufmax)
+{
+	const struct fscache_netfs *netfs = cookie_netfs_data;
+	unsigned klen;
+
+	_enter("{%s.%u},", netfs->name, netfs->version);
+
+	klen = strlen(netfs->name);
+	if (klen > bufmax)
+		return 0;
+
+	memcpy(buffer, netfs->name, klen);
+	return klen;
+}
+
+/*
+ * get the auxiliary data for an FSDEF index record - this is the index
+ * structure version number of the netfs for which this version is created
+ */
+static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
+					    void *buffer, uint16_t bufmax)
+{
+	const struct fscache_netfs *netfs = cookie_netfs_data;
+	unsigned dlen;
+
+	_enter("{%s.%u},", netfs->name, netfs->version);
+
+	dlen = sizeof(uint32_t);
+	if (dlen > bufmax)
+		return 0;
+
+	memcpy(buffer, &netfs->version, dlen);
+	return dlen;
+}
+
+/*
+ * check that the index structure version number stored in the auxiliary data
+ * matches the one the netfs gave us
+ */
+static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
+	void *cookie_netfs_data,
+	const void *data,
+	uint16_t datalen)
+{
+	struct fscache_netfs *netfs = cookie_netfs_data;
+	uint32_t version;
+
+	_enter("{%s},,%hu", netfs->name, datalen);
+
+	if (datalen != sizeof(version)) {
+		_leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
+		return FSCACHE_CHECKAUX_OBSOLETE;
+	}
+
+	memcpy(&version, data, sizeof(version));
+	if (version != netfs->version) {
+		_leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
+		return FSCACHE_CHECKAUX_OBSOLETE;
+	}
+
+	_leave(" = OKAY");
+	return FSCACHE_CHECKAUX_OKAY;
+}
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 16f9f1f46e4..4113af8d166 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -27,6 +27,12 @@
 #define FSCACHE_MIN_THREADS	4
 #define FSCACHE_MAX_THREADS	32
 
+/*
+ * fsc-fsdef.c
+ */
+extern struct fscache_cookie fscache_fsdef_index;
+extern struct fscache_cookie_def fscache_fsdef_netfs_def;
+
 /*
  * fsc-histogram.c
  */