summaryrefslogtreecommitdiff
path: root/mm/cleancache.c
blob: 2397f7c36cc723abacd3e6e1d28a54f0850c3d88 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Cleancache frontend
 *
 * This code provides the generic "frontend" layer to call a matching
 * "backend" driver implementation of cleancache.  See
 * Documentation/vm/cleancache.rst for more information.
 *
 * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
 * Author: Dan Magenheimer
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/exportfs.h>
#include <linux/mm.h>
#include <linux/debugfs.h>
#include <linux/cleancache.h>

/*
 * cleancache_ops is set by cleancache_register_ops to contain the pointers
 * to the cleancache "backend" implementation functions.
 */
static const struct cleancache_ops *cleancache_ops __read_mostly;

/*
 * Counters available via /sys/kernel/debug/cleancache (if debugfs is
 * properly configured.  These are for information only so are not protected
 * against increment races.
 */
static u64 cleancache_succ_gets;
static u64 cleancache_failed_gets;
static u64 cleancache_puts;
static u64 cleancache_invalidates;

static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
{
	switch (sb->cleancache_poolid) {
	case CLEANCACHE_NO_BACKEND:
		__cleancache_init_fs(sb);
		break;
	case CLEANCACHE_NO_BACKEND_SHARED:
		__cleancache_init_shared_fs(sb);
		break;
	}
}

/*
 * Register operations for cleancache. Returns 0 on success.
 */
int cleancache_register_ops(const struct cleancache_ops *ops)
{
	if (cmpxchg(&cleancache_ops, NULL, ops))
		return -EBUSY;

	/*
	 * A cleancache backend can be built as a module and hence loaded after
	 * a cleancache enabled filesystem has called cleancache_init_fs. To
	 * handle such a scenario, here we call ->init_fs or ->init_shared_fs
	 * for each active super block. To differentiate between local and
	 * shared filesystems, we temporarily initialize sb->cleancache_poolid
	 * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
	 * respectively in case there is no backend registered at the time
	 * cleancache_init_fs or cleancache_init_shared_fs is called.
	 *
	 * Since filesystems can be mounted concurrently with cleancache
	 * backend registration, we have to be careful to guarantee that all
	 * cleancache enabled filesystems that has been mounted by the time
	 * cleancache_register_ops is called has got and all mounted later will
	 * get cleancache_poolid. This is assured by the following statements
	 * tied together:
	 *
	 * a) iterate_supers skips only those super blocks that has started
	 *    ->kill_sb
	 *
	 * b) if iterate_supers encounters a super block that has not finished
	 *    ->mount yet, it waits until it is finished
	 *
	 * c) cleancache_init_fs is called from ->mount and
	 *    cleancache_invalidate_fs is called from ->kill_sb
	 *
	 * d) we call iterate_supers after cleancache_ops has been set
	 *
	 * From a) it follows that if iterate_supers skips a super block, then
	 * either the super block is already dead, in which case we do not need
	 * to bother initializing cleancache for it, or it was mounted after we
	 * initiated iterate_supers. In the latter case, it must have seen
	 * cleancache_ops set according to d) and initialized cleancache from
	 * ->mount by itself according to c). This proves that we call
	 * ->init_fs at least once for each active super block.
	 *
	 * From b) and c) it follows that if iterate_supers encounters a super
	 * block that has already started ->init_fs, it will wait until ->mount
	 * and hence ->init_fs has finished, then check cleancache_poolid, see
	 * that it has already been set and therefore do nothing. This proves
	 * that we call ->init_fs no more than once for each super block.
	 *
	 * Combined together, the last two paragraphs prove the function
	 * correctness.
	 *
	 * Note that various cleancache callbacks may proceed before this
	 * function is called or even concurrently with it, but since
	 * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
	 * until the corresponding ->init_fs has been actually called and
	 * cleancache_ops has been set.
	 */
	iterate_supers(cleancache_register_ops_sb, NULL);
	return 0;
}
EXPORT_SYMBOL(cleancache_register_ops);

/* Called by a cleancache-enabled filesystem at time of mount */
void __cleancache_init_fs(struct super_block *sb)
{
	int pool_id = CLEANCACHE_NO_BACKEND;

	if (cleancache_ops) {
		pool_id = cleancache_ops->init_fs(PAGE_SIZE);
		if (pool_id < 0)
			pool_id = CLEANCACHE_NO_POOL;
	}
	sb->cleancache_poolid = pool_id;
}
EXPORT_SYMBOL(__cleancache_init_fs);

/* Called by a cleancache-enabled clustered filesystem at time of mount */
void __cleancache_init_shared_fs(struct super_block *sb)
{
	int pool_id = CLEANCACHE_NO_BACKEND_SHARED;

	if (cleancache_ops) {
		pool_id = cleancache_ops->init_shared_fs(&sb->s_uuid, PAGE_SIZE);
		if (pool_id < 0)
			pool_id = CLEANCACHE_NO_POOL;
	}
	sb->cleancache_poolid = pool_id;
}
EXPORT_SYMBOL(__cleancache_init_shared_fs);

/*
 * If the filesystem uses exportable filehandles, use the filehandle as
 * the key, else use the inode number.
 */
static int cleancache_get_key(struct inode *inode,
			      struct cleancache_filekey *key)
{
	int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
	int len = 0, maxlen = CLEANCACHE_KEY_MAX;
	struct super_block *sb = inode->i_sb;

	key->u.ino = inode->i_ino;
	if (sb->s_export_op != NULL) {
		fhfn = sb->s_export_op->encode_fh;
		if  (fhfn) {
			len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
			if (len <= FILEID_ROOT || len == FILEID_INVALID)
				return -1;
			if (maxlen > CLEANCACHE_KEY_MAX)
				return -1;
		}
	}
	return 0;
}

/*
 * "Get" data from cleancache associated with the poolid/inode/index
 * that were specified when the data was put to cleanache and, if
 * successful, use it to fill the specified page with data and return 0.
 * The pageframe is unchanged and returns -1 if the get fails.
 * Page must be locked by caller.
 *
 * The function has two checks before any action is taken - whether
 * a backend is registered and whether the sb->cleancache_poolid
 * is correct.
 */
int __cleancache_get_page(struct page *page)
{
	int ret = -1;
	int pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops) {
		cleancache_failed_gets++;
		goto out;
	}

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	pool_id = page->mapping->host->i_sb->cleancache_poolid;
	if (pool_id < 0)
		goto out;

	if (cleancache_get_key(page->mapping->host, &key) < 0)
		goto out;

	ret = cleancache_ops->get_page(pool_id, key, page->index, page);
	if (ret == 0)
		cleancache_succ_gets++;
	else
		cleancache_failed_gets++;
out:
	return ret;
}
EXPORT_SYMBOL(__cleancache_get_page);

/*
 * "Put" data from a page to cleancache and associate it with the
 * (previously-obtained per-filesystem) poolid and the page's,
 * inode and page index.  Page must be locked.  Note that a put_page
 * always "succeeds", though a subsequent get_page may succeed or fail.
 *
 * The function has two checks before any action is taken - whether
 * a backend is registered and whether the sb->cleancache_poolid
 * is correct.
 */
void __cleancache_put_page(struct page *page)
{
	int pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops) {
		cleancache_puts++;
		return;
	}

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	pool_id = page->mapping->host->i_sb->cleancache_poolid;
	if (pool_id >= 0 &&
		cleancache_get_key(page->mapping->host, &key) >= 0) {
		cleancache_ops->put_page(pool_id, key, page->index, page);
		cleancache_puts++;
	}
}
EXPORT_SYMBOL(__cleancache_put_page);

/*
 * Invalidate any data from cleancache associated with the poolid and the
 * page's inode and page index so that a subsequent "get" will fail.
 *
 * The function has two checks before any action is taken - whether
 * a backend is registered and whether the sb->cleancache_poolid
 * is correct.
 */
void __cleancache_invalidate_page(struct address_space *mapping,
					struct page *page)
{
	/* careful... page->mapping is NULL sometimes when this is called */
	int pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops)
		return;

	if (pool_id >= 0) {
		VM_BUG_ON_PAGE(!PageLocked(page), page);
		if (cleancache_get_key(mapping->host, &key) >= 0) {
			cleancache_ops->invalidate_page(pool_id,
					key, page->index);
			cleancache_invalidates++;
		}
	}
}
EXPORT_SYMBOL(__cleancache_invalidate_page);

/*
 * Invalidate all data from cleancache associated with the poolid and the
 * mappings's inode so that all subsequent gets to this poolid/inode
 * will fail.
 *
 * The function has two checks before any action is taken - whether
 * a backend is registered and whether the sb->cleancache_poolid
 * is correct.
 */
void __cleancache_invalidate_inode(struct address_space *mapping)
{
	int pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops)
		return;

	if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
		cleancache_ops->invalidate_inode(pool_id, key);
}
EXPORT_SYMBOL(__cleancache_invalidate_inode);

/*
 * Called by any cleancache-enabled filesystem at time of unmount;
 * note that pool_id is surrendered and may be returned by a subsequent
 * cleancache_init_fs or cleancache_init_shared_fs.
 */
void __cleancache_invalidate_fs(struct super_block *sb)
{
	int pool_id;

	pool_id = sb->cleancache_poolid;
	sb->cleancache_poolid = CLEANCACHE_NO_POOL;

	if (cleancache_ops && pool_id >= 0)
		cleancache_ops->invalidate_fs(pool_id);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);

static int __init init_cleancache(void)
{
#ifdef CONFIG_DEBUG_FS
	struct dentry *root = debugfs_create_dir("cleancache", NULL);
	if (root == NULL)
		return -ENXIO;
	debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets);
	debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets);
	debugfs_create_u64("puts", 0444, root, &cleancache_puts);
	debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates);
#endif
	return 0;
}
module_init(init_cleancache)