1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Cleancache frontend
4 *
5 * This code provides the generic "frontend" layer to call a matching
6 * "backend" driver implementation of cleancache. See
7 * Documentation/vm/cleancache.rst for more information.
8 *
9 * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
10 * Author: Dan Magenheimer
11 */
12
13 #include <linux/module.h>
14 #include <linux/fs.h>
15 #include <linux/exportfs.h>
16 #include <linux/mm.h>
17 #include <linux/debugfs.h>
18 #include <linux/cleancache.h>
19
20 /*
21 * cleancache_ops is set by cleancache_register_ops to contain the pointers
22 * to the cleancache "backend" implementation functions.
23 */
24 static const struct cleancache_ops *cleancache_ops __read_mostly;
25
26 /*
27 * Counters available via /sys/kernel/debug/cleancache (if debugfs is
28 * properly configured. These are for information only so are not protected
29 * against increment races.
30 */
31 static u64 cleancache_succ_gets;
32 static u64 cleancache_failed_gets;
33 static u64 cleancache_puts;
34 static u64 cleancache_invalidates;
35
36 static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
37 {
38 switch (sb->cleancache_poolid) {
39 case CLEANCACHE_NO_BACKEND:
40 __cleancache_init_fs(sb);
41 break;
42 case CLEANCACHE_NO_BACKEND_SHARED:
43 __cleancache_init_shared_fs(sb);
44 break;
45 }
46 }
47
48 /*
49 * Register operations for cleancache. Returns 0 on success.
50 */
51 int cleancache_register_ops(const struct cleancache_ops *ops)
52 {
53 if (cmpxchg(&cleancache_ops, NULL, ops))
54 return -EBUSY;
55
56 /*
57 * A cleancache backend can be built as a module and hence loaded after
58 * a cleancache enabled filesystem has called cleancache_init_fs. To
59 * handle such a scenario, here we call ->init_fs or ->init_shared_fs
60 * for each active super block. To differentiate between local and
61 * shared filesystems, we temporarily initialize sb->cleancache_poolid
62 * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
63 * respectively in case there is no backend registered at the time
64 * cleancache_init_fs or cleancache_init_shared_fs is called.
65 *
66 * Since filesystems can be mounted concurrently with cleancache
67 * backend registration, we have to be careful to guarantee that all
68 * cleancache enabled filesystems that has been mounted by the time
69 * cleancache_register_ops is called has got and all mounted later will
70 * get cleancache_poolid. This is assured by the following statements
71 * tied together:
72 *
73 * a) iterate_supers skips only those super blocks that has started
74 * ->kill_sb
75 *
76 * b) if iterate_supers encounters a super block that has not finished
77 * ->mount yet, it waits until it is finished
78 *
79 * c) cleancache_init_fs is called from ->mount and
80 * cleancache_invalidate_fs is called from ->kill_sb
81 *
82 * d) we call iterate_supers after cleancache_ops has been set
83 *
84 * From a) it follows that if iterate_supers skips a super block, then
85 * either the super block is already dead, in which case we do not need
86 * to bother initializing cleancache for it, or it was mounted after we
87 * initiated iterate_supers. In the latter case, it must have seen
88 * cleancache_ops set according to d) and initialized cleancache from
89 * ->mount by itself according to c). This proves that we call
90 * ->init_fs at least once for each active super block.
91 *
92 * From b) and c) it follows that if iterate_supers encounters a super
93 * block that has already started ->init_fs, it will wait until ->mount
94 * and hence ->init_fs has finished, then check cleancache_poolid, see
95 * that it has already been set and therefore do nothing. This proves
96 * that we call ->init_fs no more than once for each super block.
97 *
98 * Combined together, the last two paragraphs prove the function
99 * correctness.
100 *
101 * Note that various cleancache callbacks may proceed before this
102 * function is called or even concurrently with it, but since
103 * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
104 * until the corresponding ->init_fs has been actually called and
105 * cleancache_ops has been set.
106 */
107 iterate_supers(cleancache_register_ops_sb, NULL);
108 return 0;
109 }
110 EXPORT_SYMBOL(cleancache_register_ops);
111
112 /* Called by a cleancache-enabled filesystem at time of mount */
113 void __cleancache_init_fs(struct super_block *sb)
114 {
115 int pool_id = CLEANCACHE_NO_BACKEND;
116
117 if (cleancache_ops) {
118 pool_id = cleancache_ops->init_fs(PAGE_SIZE);
119 if (pool_id < 0)
120 pool_id = CLEANCACHE_NO_POOL;
121 }
122 sb->cleancache_poolid = pool_id;
123 }
124 EXPORT_SYMBOL(__cleancache_init_fs);
125
126 /* Called by a cleancache-enabled clustered filesystem at time of mount */
127 void __cleancache_init_shared_fs(struct super_block *sb)
128 {
129 int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
130
131 if (cleancache_ops) {
132 pool_id = cleancache_ops->init_shared_fs(&sb->s_uuid, PAGE_SIZE);
133 if (pool_id < 0)
134 pool_id = CLEANCACHE_NO_POOL;
135 }
136 sb->cleancache_poolid = pool_id;
137 }
138 EXPORT_SYMBOL(__cleancache_init_shared_fs);
139
140 /*
141 * If the filesystem uses exportable filehandles, use the filehandle as
142 * the key, else use the inode number.
143 */
144 static int cleancache_get_key(struct inode *inode,
145 struct cleancache_filekey *key)
146 {
147 int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
148 int len = 0, maxlen = CLEANCACHE_KEY_MAX;
149 struct super_block *sb = inode->i_sb;
150
151 key->u.ino = inode->i_ino;
152 if (sb->s_export_op != NULL) {
153 fhfn = sb->s_export_op->encode_fh;
154 if (fhfn) {
155 len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
156 if (len <= FILEID_ROOT || len == FILEID_INVALID)
157 return -1;
158 if (maxlen > CLEANCACHE_KEY_MAX)
159 return -1;
160 }
161 }
162 return 0;
163 }
164
165 /*
166 * "Get" data from cleancache associated with the poolid/inode/index
167 * that were specified when the data was put to cleanache and, if
168 * successful, use it to fill the specified page with data and return 0.
169 * The pageframe is unchanged and returns -1 if the get fails.
170 * Page must be locked by caller.
171 *
172 * The function has two checks before any action is taken - whether
173 * a backend is registered and whether the sb->cleancache_poolid
174 * is correct.
175 */
176 int __cleancache_get_page(struct page *page)
177 {
178 int ret = -1;
179 int pool_id;
180 struct cleancache_filekey key = { .u.key = { 0 } };
181
182 if (!cleancache_ops) {
183 cleancache_failed_gets++;
184 goto out;
185 }
186
187 VM_BUG_ON_PAGE(!PageLocked(page), page);
188 pool_id = page->mapping->host->i_sb->cleancache_poolid;
189 if (pool_id < 0)
190 goto out;
191
192 if (cleancache_get_key(page->mapping->host, &key) < 0)
193 goto out;
194
195 ret = cleancache_ops->get_page(pool_id, key, page->index, page);
196 if (ret == 0)
197 cleancache_succ_gets++;
198 else
199 cleancache_failed_gets++;
200 out:
201 return ret;
202 }
203 EXPORT_SYMBOL(__cleancache_get_page);
204
205 /*
206 * "Put" data from a page to cleancache and associate it with the
207 * (previously-obtained per-filesystem) poolid and the page's,
208 * inode and page index. Page must be locked. Note that a put_page
209 * always "succeeds", though a subsequent get_page may succeed or fail.
210 *
211 * The function has two checks before any action is taken - whether
212 * a backend is registered and whether the sb->cleancache_poolid
213 * is correct.
214 */
215 void __cleancache_put_page(struct page *page)
216 {
217 int pool_id;
218 struct cleancache_filekey key = { .u.key = { 0 } };
219
220 if (!cleancache_ops) {
221 cleancache_puts++;
222 return;
223 }
224
225 VM_BUG_ON_PAGE(!PageLocked(page), page);
226 pool_id = page->mapping->host->i_sb->cleancache_poolid;
227 if (pool_id >= 0 &&
228 cleancache_get_key(page->mapping->host, &key) >= 0) {
229 cleancache_ops->put_page(pool_id, key, page->index, page);
230 cleancache_puts++;
231 }
232 }
233 EXPORT_SYMBOL(__cleancache_put_page);
234
235 /*
236 * Invalidate any data from cleancache associated with the poolid and the
237 * page's inode and page index so that a subsequent "get" will fail.
238 *
239 * The function has two checks before any action is taken - whether
240 * a backend is registered and whether the sb->cleancache_poolid
241 * is correct.
242 */
243 void __cleancache_invalidate_page(struct address_space *mapping,
244 struct page *page)
245 {
246 /* careful... page->mapping is NULL sometimes when this is called */
247 int pool_id = mapping->host->i_sb->cleancache_poolid;
248 struct cleancache_filekey key = { .u.key = { 0 } };
249
250 if (!cleancache_ops)
251 return;
252
253 if (pool_id >= 0) {
254 VM_BUG_ON_PAGE(!PageLocked(page), page);
255 if (cleancache_get_key(mapping->host, &key) >= 0) {
256 cleancache_ops->invalidate_page(pool_id,
257 key, page->index);
258 cleancache_invalidates++;
259 }
260 }
261 }
262 EXPORT_SYMBOL(__cleancache_invalidate_page);
263
264 /*
265 * Invalidate all data from cleancache associated with the poolid and the
266 * mappings's inode so that all subsequent gets to this poolid/inode
267 * will fail.
268 *
269 * The function has two checks before any action is taken - whether
270 * a backend is registered and whether the sb->cleancache_poolid
271 * is correct.
272 */
273 void __cleancache_invalidate_inode(struct address_space *mapping)
274 {
275 int pool_id = mapping->host->i_sb->cleancache_poolid;
276 struct cleancache_filekey key = { .u.key = { 0 } };
277
278 if (!cleancache_ops)
279 return;
280
281 if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
282 cleancache_ops->invalidate_inode(pool_id, key);
283 }
284 EXPORT_SYMBOL(__cleancache_invalidate_inode);
285
286 /*
287 * Called by any cleancache-enabled filesystem at time of unmount;
288 * note that pool_id is surrendered and may be returned by a subsequent
289 * cleancache_init_fs or cleancache_init_shared_fs.
290 */
291 void __cleancache_invalidate_fs(struct super_block *sb)
292 {
293 int pool_id;
294
295 pool_id = sb->cleancache_poolid;
296 sb->cleancache_poolid = CLEANCACHE_NO_POOL;
297
298 if (cleancache_ops && pool_id >= 0)
299 cleancache_ops->invalidate_fs(pool_id);
300 }
301 EXPORT_SYMBOL(__cleancache_invalidate_fs);
302
303 static int __init init_cleancache(void)
304 {
305 #ifdef CONFIG_DEBUG_FS
306 struct dentry *root = debugfs_create_dir("cleancache", NULL);
307
308 debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets);
309 debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets);
310 debugfs_create_u64("puts", 0444, root, &cleancache_puts);
311 debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates);
312 #endif
313 return 0;
314 }
315 module_init(init_cleancache)