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