fsdef.c
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/* 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),
.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,
};
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;
}