linux/fs/fscache/fsdef.c
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   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 uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
  17                                            void *buffer, uint16_t bufmax);
  18
  19static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
  20                                            void *buffer, uint16_t bufmax);
  21
  22static
  23enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
  24                                                    const void *data,
  25                                                    uint16_t datalen);
  26
  27/*
  28 * The root index is owned by FS-Cache itself.
  29 *
  30 * When a netfs requests caching facilities, FS-Cache will, if one doesn't
  31 * already exist, create an entry in the root index with the key being the name
  32 * of the netfs ("AFS" for example), and the auxiliary data holding the index
  33 * structure version supplied by the netfs:
  34 *
  35 *                                   FSDEF
  36 *                                     |
  37 *                               +-----------+
  38 *                               |           |
  39 *                              NFS         AFS
  40 *                             [v=1]       [v=1]
  41 *
  42 * If an entry with the appropriate name does already exist, the version is
  43 * compared.  If the version is different, the entire subtree from that entry
  44 * will be discarded and a new entry created.
  45 *
  46 * The new entry will be an index, and a cookie referring to it will be passed
  47 * to the netfs.  This is then the root handle by which the netfs accesses the
  48 * cache.  It can create whatever objects it likes in that index, including
  49 * further indices.
  50 */
  51static struct fscache_cookie_def fscache_fsdef_index_def = {
  52        .name           = ".FS-Cache",
  53        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  54};
  55
  56struct fscache_cookie fscache_fsdef_index = {
  57        .usage          = ATOMIC_INIT(1),
  58        .lock           = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
  59        .backing_objects = HLIST_HEAD_INIT,
  60        .def            = &fscache_fsdef_index_def,
  61};
  62EXPORT_SYMBOL(fscache_fsdef_index);
  63
  64/*
  65 * Definition of an entry in the root index.  Each entry is an index, keyed to
  66 * a specific netfs and only applicable to a particular version of the index
  67 * structure used by that netfs.
  68 */
  69struct fscache_cookie_def fscache_fsdef_netfs_def = {
  70        .name           = "FSDEF.netfs",
  71        .type           = FSCACHE_COOKIE_TYPE_INDEX,
  72        .get_key        = fscache_fsdef_netfs_get_key,
  73        .get_aux        = fscache_fsdef_netfs_get_aux,
  74        .check_aux      = fscache_fsdef_netfs_check_aux,
  75};
  76
  77/*
  78 * get the key data for an FSDEF index record - this is the name of the netfs
  79 * for which this entry is created
  80 */
  81static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
  82                                            void *buffer, uint16_t bufmax)
  83{
  84        const struct fscache_netfs *netfs = cookie_netfs_data;
  85        unsigned klen;
  86
  87        _enter("{%s.%u},", netfs->name, netfs->version);
  88
  89        klen = strlen(netfs->name);
  90        if (klen > bufmax)
  91                return 0;
  92
  93        memcpy(buffer, netfs->name, klen);
  94        return klen;
  95}
  96
  97/*
  98 * get the auxiliary data for an FSDEF index record - this is the index
  99 * structure version number of the netfs for which this version is created
 100 */
 101static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
 102                                            void *buffer, uint16_t bufmax)
 103{
 104        const struct fscache_netfs *netfs = cookie_netfs_data;
 105        unsigned dlen;
 106
 107        _enter("{%s.%u},", netfs->name, netfs->version);
 108
 109        dlen = sizeof(uint32_t);
 110        if (dlen > bufmax)
 111                return 0;
 112
 113        memcpy(buffer, &netfs->version, dlen);
 114        return dlen;
 115}
 116
 117/*
 118 * check that the index structure version number stored in the auxiliary data
 119 * matches the one the netfs gave us
 120 */
 121static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
 122        void *cookie_netfs_data,
 123        const void *data,
 124        uint16_t datalen)
 125{
 126        struct fscache_netfs *netfs = cookie_netfs_data;
 127        uint32_t version;
 128
 129        _enter("{%s},,%hu", netfs->name, datalen);
 130
 131        if (datalen != sizeof(version)) {
 132                _leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
 133                return FSCACHE_CHECKAUX_OBSOLETE;
 134        }
 135
 136        memcpy(&version, data, sizeof(version));
 137        if (version != netfs->version) {
 138                _leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
 139                return FSCACHE_CHECKAUX_OBSOLETE;
 140        }
 141
 142        _leave(" = OKAY");
 143        return FSCACHE_CHECKAUX_OKAY;
 144}
 145
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