3 files changed, 151 insertions, 0 deletions

diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 1384823a160c..bc1f3b9d811a 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 000000000000..f5b4baee7352
--- /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 16f9f1f46e4d..4113af8d1660 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -28,6 +28,12 @@
 #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
  */
 #ifdef CONFIG_FSCACHE_HISTOGRAM