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authorDavid Howells <dhowells@redhat.com>2009-04-03 11:42:37 -0400
committerDavid Howells <dhowells@redhat.com>2009-04-03 11:42:37 -0400
commita6891645cf2ddd4778096848a864580e7258faba (patch)
treee0095e8b87e199e7310508fc3687660746860600 /fs/fscache/fsdef.c
parent7394daa8c61dfda4baa687f133748fa0b599b017 (diff)
FS-Cache: Root index definition
Add a description of the root index of the cache for later patches to make use of. 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. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
Diffstat (limited to 'fs/fscache/fsdef.c')
-rw-r--r--fs/fscache/fsdef.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/fs/fscache/fsdef.c b/fs/fscache/fsdef.c
new file mode 100644
index 000000000000..f5b4baee7352
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+++ b/fs/fscache/fsdef.c
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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}