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 .lock = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
59 .backing_objects = HLIST_HEAD_INIT,
60 .def = &fscache_fsdef_index_def,
61 };
62 EXPORT_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 */
69 struct 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 */
fscache_fsdef_netfs_get_key(const void * cookie_netfs_data,void * buffer,uint16_t bufmax)81 static 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 */
fscache_fsdef_netfs_get_aux(const void * cookie_netfs_data,void * buffer,uint16_t bufmax)101 static 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 */
fscache_fsdef_netfs_check_aux(void * cookie_netfs_data,const void * data,uint16_t datalen)121 static 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