// SPDX-License-Identifier: GPL-2.0-or-later
  /* Filesystem index definition
   *
   * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   */
  
  #define FSCACHE_DEBUG_LEVEL CACHE
  #include <linux/module.h>
  #include "internal.h"
  
  static
  enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
  						    const void *data,
  						    uint16_t datalen,
  						    loff_t object_size);
  
  /*
   * 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),
  	.n_active	= ATOMIC_INIT(1),
  	.lock		= __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
  	.backing_objects = HLIST_HEAD_INIT,
  	.def		= &fscache_fsdef_index_def,
  	.flags		= 1 << FSCACHE_COOKIE_ENABLED,
  	.type		= FSCACHE_COOKIE_TYPE_INDEX,
  };
  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,
  	.check_aux	= fscache_fsdef_netfs_check_aux,
  };
  
  /*
   * 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,
  	loff_t object_size)
  {
  	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;
  }