fs/fscache/fsdef.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Filesystem index definition
   3  *
   4  * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define FSCACHE_DEBUG_LEVEL CACHE
   9 #include <linux/module.h>
  10 #include "internal.h"
  11
  12 static
  13 enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
  14                                                     const void *data,
  15                                                     uint16_t datalen,
  16                                                     loff_t object_size);
  17
  18 /*
  19  * The root index is owned by FS-Cache itself.
  20  *
  21  * When a netfs requests caching facilities, FS-Cache will, if one doesn't
  22  * already exist, create an entry in the root index with the key being the name
  23  * of the netfs ("AFS" for example), and the auxiliary data holding the index
  24  * structure version supplied by the netfs:
  25  *
  26  *                                   FSDEF
  27  *                                     |
  28  *                               +-----------+
  29  *                               |           |
  30  *                              NFS         AFS
  31  *                             [v=1]       [v=1]
  32  *
  33  * If an entry with the appropriate name does already exist, the version is
  34  * compared.  If the version is different, the entire subtree from that entry
  35  * will be discarded and a new entry created.
  36  *
  37  * The new entry will be an index, and a cookie referring to it will be passed
  38  * to the netfs.  This is then the root handle by which the netfs accesses the
  39  * cache.  It can create whatever objects it likes in that index, including
  40  * further indices.
  41  */
  42 static struct fscache_cookie_def fscache_fsdef_index_def = {
  43         .name           = ".FS-Cache",
  44         .type           = FSCACHE_COOKIE_TYPE_INDEX,
  45 };
  46
  47 struct fscache_cookie fscache_fsdef_index = {
  48         .usage          = ATOMIC_INIT(1),
  49         .n_active       = ATOMIC_INIT(1),
  50         .lock           = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
  51         .backing_objects = HLIST_HEAD_INIT,
  52         .def            = &fscache_fsdef_index_def,
  53         .flags          = 1 << FSCACHE_COOKIE_ENABLED,
  54         .type           = FSCACHE_COOKIE_TYPE_INDEX,
  55 };
  56 EXPORT_SYMBOL(fscache_fsdef_index);
  57
  58 /*
  59  * Definition of an entry in the root index.  Each entry is an index, keyed to
  60  * a specific netfs and only applicable to a particular version of the index
  61  * structure used by that netfs.
  62  */
  63 struct fscache_cookie_def fscache_fsdef_netfs_def = {
  64         .name           = "FSDEF.netfs",
  65         .type           = FSCACHE_COOKIE_TYPE_INDEX,
  66         .check_aux      = fscache_fsdef_netfs_check_aux,
  67 };
  68
  69 /*
  70  * check that the index structure version number stored in the auxiliary data
  71  * matches the one the netfs gave us
  72  */
  73 static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
  74         void *cookie_netfs_data,
  75         const void *data,
  76         uint16_t datalen,
  77         loff_t object_size)
  78 {
  79         struct fscache_netfs *netfs = cookie_netfs_data;
  80         uint32_t version;
  81
  82         _enter("{%s},,%hu", netfs->name, datalen);
  83
  84         if (datalen != sizeof(version)) {
  85                 _leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
  86                 return FSCACHE_CHECKAUX_OBSOLETE;
  87         }
  88
  89         memcpy(&version, data, sizeof(version));
  90         if (version != netfs->version) {
  91                 _leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
  92                 return FSCACHE_CHECKAUX_OBSOLETE;
  93         }
  94
  95         _leave(" = OKAY");
  96         return FSCACHE_CHECKAUX_OKAY;
  97 }