LXR linux/fs/fscache/fsdef.c

   1/* Filesystem index definition
   2 *
   3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#define FSCACHE_DEBUG_LEVEL CACHE
  13#include <linux/module.h>
  14#include "internal.h"
  15
  16static
  17enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
  18                                                    const void *data,
  19                                                    uint16_t datalen,
  20                                                    loff_t object_size);
  21
  22/*
  23 * The root index is owned by FS-Cache itself.
  24 *
  25 * When a netfs requests caching facilities, FS-Cache will, if one doesn't
  26 * already exist, create an entry in the root index with the key being the name
  27 * of the netfs ("AFS" for example), and the auxiliary data holding the index
  28 * structure version supplied by the netfs:
  29 *
  30 *                                   FSDEF
  31 *                                     |
  32 *                               +-----------+
  33 *                               |           |
  34 *                              NFS         AFS
  35 *                             [v=1]       [v=1]
  36 *
  37 * If an entry with the appropriate name does already exist, the version is
  38 * compared.  If the version is different, the entire subtree from that entry
  39 * will be discarded and a new entry created.
  40 *
  41 * The new entry will be an index, and a cookie referring to it will be passed
  42 * to the netfs.  This is then the root handle by which the netfs accesses the
  43 * cache.  It can create whatever objects it likes in that index, including
  44 * further indices.
  45 */
  46static struct fscache_cookie_def fscache_fsdef_index_def = {
  47        .name           = ".FS-Cache",
  48        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  49};
  50
  51struct fscache_cookie fscache_fsdef_index = {
  52        .usage          = ATOMIC_INIT(1),
  53        .n_active       = ATOMIC_INIT(1),
  54        .lock           = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
  55        .backing_objects = HLIST_HEAD_INIT,
  56        .def            = &fscache_fsdef_index_def,
  57        .flags          = 1 << FSCACHE_COOKIE_ENABLED,
  58        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  59};
  60EXPORT_SYMBOL(fscache_fsdef_index);
  61
  62/*
  63 * Definition of an entry in the root index.  Each entry is an index, keyed to
  64 * a specific netfs and only applicable to a particular version of the index
  65 * structure used by that netfs.
  66 */
  67struct fscache_cookie_def fscache_fsdef_netfs_def = {
  68        .name           = "FSDEF.netfs",
  69        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  70        .check_aux      = fscache_fsdef_netfs_check_aux,
  71};
  72
  73/*
  74 * check that the index structure version number stored in the auxiliary data
  75 * matches the one the netfs gave us
  76 */
  77static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
  78        void *cookie_netfs_data,
  79        const void *data,
  80        uint16_t datalen,
  81        loff_t object_size)
  82{
  83        struct fscache_netfs *netfs = cookie_netfs_data;
  84        uint32_t version;
  85
  86        _enter("{%s},,%hu", netfs->name, datalen);
  87
  88        if (datalen != sizeof(version)) {
  89                _leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
  90                return FSCACHE_CHECKAUX_OBSOLETE;
  91        }
  92
  93        memcpy(&version, data, sizeof(version));
  94        if (version != netfs->version) {
  95                _leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
  96                return FSCACHE_CHECKAUX_OBSOLETE;
  97        }
  98
  99        _leave(" = OKAY");
 100        return FSCACHE_CHECKAUX_OKAY;
 101}
 102