1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Filesystem index definition
3 *
4 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #define FSCACHE_DEBUG_LEVEL CACHE
9 #include <linux/module.h>
10 #include "internal.h"
11
12 static
13 enum fscache_checkaux fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
14 const void *data,
15 uint16_t datalen,
16 loff_t object_size);
17
18 /*
19 * The root index is owned by FS-Cache itself.
20 *
21 * When a netfs requests caching facilities, FS-Cache will, if one doesn't
22 * already exist, create an entry in the root index with the key being the name
23 * of the netfs ("AFS" for example), and the auxiliary data holding the index
24 * structure version supplied by the netfs:
25 *
26 * FSDEF
27 * |
28 * +-----------+
29 * | |
30 * NFS AFS
31 * [v=1] [v=1]
32 *
33 * If an entry with the appropriate name does already exist, the version is
34 * compared. If the version is different, the entire subtree from that entry
35 * will be discarded and a new entry created.
36 *
37 * The new entry will be an index, and a cookie referring to it will be passed
38 * to the netfs. This is then the root handle by which the netfs accesses the
39 * cache. It can create whatever objects it likes in that index, including
40 * further indices.
41 */
42 static struct fscache_cookie_def fscache_fsdef_index_def = {
43 .name = ".FS-Cache",
44 .type = FSCACHE_COOKIE_TYPE_INDEX,
45 };
46
47 struct fscache_cookie fscache_fsdef_index = {
48 .usage = ATOMIC_INIT(1),
49 .n_active = ATOMIC_INIT(1),
50 .lock = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
51 .backing_objects = HLIST_HEAD_INIT,
52 .def = &fscache_fsdef_index_def,
53 .flags = 1 << FSCACHE_COOKIE_ENABLED,
54 .type = FSCACHE_COOKIE_TYPE_INDEX,
55 };
56 EXPORT_SYMBOL(fscache_fsdef_index);
57
58 /*
59 * Definition of an entry in the root index. Each entry is an index, keyed to
60 * a specific netfs and only applicable to a particular version of the index
61 * structure used by that netfs.
62 */
63 struct fscache_cookie_def fscache_fsdef_netfs_def = {
64 .name = "FSDEF.netfs",
65 .type = FSCACHE_COOKIE_TYPE_INDEX,
66 .check_aux = fscache_fsdef_netfs_check_aux,
67 };
68
69 /*
70 * check that the index structure version number stored in the auxiliary data
71 * matches the one the netfs gave us
72 */
73 static enum fscache_checkaux fscache_fsdef_netfs_check_aux(
74 void *cookie_netfs_data,
75 const void *data,
76 uint16_t datalen,
77 loff_t object_size)
78 {
79 struct fscache_netfs *netfs = cookie_netfs_data;
80 uint32_t version;
81
82 _enter("{%s},,%hu", netfs->name, datalen);
83
84 if (datalen != sizeof(version)) {
85 _leave(" = OBSOLETE [dl=%d v=%zu]", datalen, sizeof(version));
86 return FSCACHE_CHECKAUX_OBSOLETE;
87 }
88
89 memcpy(&version, data, sizeof(version));
90 if (version != netfs->version) {
91 _leave(" = OBSOLETE [ver=%x net=%x]", version, netfs->version);
92 return FSCACHE_CHECKAUX_OBSOLETE;
93 }
94
95 _leave(" = OKAY");
96 return FSCACHE_CHECKAUX_OKAY;
97 }