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
16 static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
17 void *buffer, uint16_t bufmax);
18
19 static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
20 void *buffer, uint16_t bufmax);
21
22 static
23 enum 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 */
51 static struct fscache_cookie_def fscache_fsdef_index_def = {
52 .name = ".FS-Cache",
53 .type = FSCACHE_COOKIE_TYPE_INDEX,
54 };
55
56 struct fscache_cookie fscache_fsdef_index = {
57 .usage = ATOMIC_INIT(1),
58 .n_active = ATOMIC_INIT(1),
59 .lock = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
60 .backing_objects = HLIST_HEAD_INIT,
61 .def = &fscache_fsdef_index_def,
62 .flags = 1 << FSCACHE_COOKIE_ENABLED,
63 };
64 EXPORT_SYMBOL(fscache_fsdef_index);
65
66 /*
67 * Definition of an entry in the root index. Each entry is an index, keyed to
68 * a specific netfs and only applicable to a particular version of the index
69 * structure used by that netfs.
70 */
71 struct fscache_cookie_def fscache_fsdef_netfs_def = {
72 .name = "FSDEF.netfs",
73 .type = FSCACHE_COOKIE_TYPE_INDEX,
74 .get_key = fscache_fsdef_netfs_get_key,
75 .get_aux = fscache_fsdef_netfs_get_aux,
76 .check_aux = fscache_fsdef_netfs_check_aux,
77 };
78
79 /*
80 * get the key data for an FSDEF index record - this is the name of the netfs
81 * for which this entry is created
82 */
fscache_fsdef_netfs_get_key(const void * cookie_netfs_data,void * buffer,uint16_t bufmax)83 static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
84 void *buffer, uint16_t bufmax)
85 {
86 const struct fscache_netfs *netfs = cookie_netfs_data;
87 unsigned klen;
88
89 _enter("{%s.%u},", netfs->name, netfs->version);
90
91 klen = strlen(netfs->name);
92 if (klen > bufmax)
93 return 0;
94
95 memcpy(buffer, netfs->name, klen);
96 return klen;
97 }
98
99 /*
100 * get the auxiliary data for an FSDEF index record - this is the index
101 * structure version number of the netfs for which this version is created
102 */
fscache_fsdef_netfs_get_aux(const void * cookie_netfs_data,void * buffer,uint16_t bufmax)103 static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
104 void *buffer, uint16_t bufmax)
105 {
106 const struct fscache_netfs *netfs = cookie_netfs_data;
107 unsigned dlen;
108
109 _enter("{%s.%u},", netfs->name, netfs->version);
110
111 dlen = sizeof(uint32_t);
112 if (dlen > bufmax)
113 return 0;
114
115 memcpy(buffer, &netfs->version, dlen);
116 return dlen;
117 }
118
119 /*
120 * check that the index structure version number stored in the auxiliary data
121 * matches the one the netfs gave us
122 */
fscache_fsdef_netfs_check_aux(void * cookie_netfs_data,const void * data,uint16_t datalen)123 static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
124 void *cookie_netfs_data,
125 const void *data,
126 uint16_t datalen)
127 {
128 struct fscache_netfs *netfs = cookie_netfs_data;
129 uint32_t version;
130
131 _enter("{%s},,%hu", netfs->name, datalen);
132
133 if (datalen != sizeof(version)) {
134 _leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
135 return FSCACHE_CHECKAUX_OBSOLETE;
136 }
137
138 memcpy(&version, data, sizeof(version));
139 if (version != netfs->version) {
140 _leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
141 return FSCACHE_CHECKAUX_OBSOLETE;
142 }
143
144 _leave(" = OKAY");
145 return FSCACHE_CHECKAUX_OKAY;
146 }
147