summaryrefslogtreecommitdiffstats
path: root/mm/cleancache.c
blob: aa10f9a3bc88c2b1774d0a4b736df3dfb7198e80 (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
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
/*
 * Cleancache frontend
 *
 * This code provides the generic "frontend" layer to call a matching
 * "backend" driver implementation of cleancache.  See
 * Documentation/vm/cleancache.txt for more information.
 *
 * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
 * Author: Dan Magenheimer
 *
 * This work is licensed under the terms of the GNU GPL, version 2.
 */

#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_ops_register to contain the pointers
 * to the cleancache "backend" implementation functions.
 */
static 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;

/*
 * When no backend is registered all calls to init_fs and init_shared_fs
 * are registered and fake poolids (FAKE_FS_POOLID_OFFSET or
 * FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array
 * [shared_|]fs_poolid_map) are given to the respective super block
 * (sb->cleancache_poolid) and no tmem_pools are created. When a backend
 * registers with cleancache the previous calls to init_fs and init_shared_fs
 * are executed to create tmem_pools and set the respective poolids. While no
 * backend is registered all "puts", "gets" and "flushes" are ignored or failed.
 */
#define MAX_INITIALIZABLE_FS 32
#define FAKE_FS_POOLID_OFFSET 1000
#define FAKE_SHARED_FS_POOLID_OFFSET 2000

#define FS_NO_BACKEND (-1)
#define FS_UNKNOWN (-2)
static int fs_poolid_map[MAX_INITIALIZABLE_FS];
static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS];
static char *uuids[MAX_INITIALIZABLE_FS];
/*
 * Mutex for the [shared_|]fs_poolid_map to guard against multiple threads
 * invoking umount (and ending in __cleancache_invalidate_fs) and also multiple
 * threads calling mount (and ending up in __cleancache_init_[shared|]fs).
 */
static DEFINE_MUTEX(poolid_mutex);
/*
 * When set to false (default) all calls to the cleancache functions, except
 * the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
 * by the if (!cleancache_ops) return. This means multiple threads (from
 * different filesystems) will be checking cleancache_ops. The usage of a
 * bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are
 * OK if the time between the backend's have been initialized (and
 * cleancache_ops has been set to not NULL) and when the filesystems start
 * actually calling the backends. The inverse (when unloading) is obviously
 * not good - but this shim does not do that (yet).
 */

/*
 * The backends and filesystems work all asynchronously. This is b/c the
 * backends can be built as modules.
 * The usual sequence of events is:
 *	a) mount /	-> __cleancache_init_fs is called. We set the
 *		[shared_|]fs_poolid_map and uuids for.
 *
 *	b). user does I/Os -> we call the rest of __cleancache_* functions
 *		which return immediately as cleancache_ops is false.
 *
 *	c). modprobe zcache -> cleancache_register_ops. We init the backend
 *		and set cleancache_ops to true, and for any fs_poolid_map
 *		(which is set by __cleancache_init_fs) we initialize the poolid.
 *
 *	d). user does I/Os -> now that cleancache_ops is true all the
 *		__cleancache_* functions can call the backend. They all check
 *		that fs_poolid_map is valid and if so invoke the backend.
 *
 *	e). umount /	-> __cleancache_invalidate_fs, the fs_poolid_map is
 *		reset (which is the second check in the __cleancache_* ops
 *		to call the backend).
 *
 * The sequence of event could also be c), followed by a), and d). and e). The
 * c) would not happen anymore. There is also the chance of c), and one thread
 * doing a) + d), and another doing e). For that case we depend on the
 * filesystem calling __cleancache_invalidate_fs in the proper sequence (so
 * that it handles all I/Os before it invalidates the fs (which is last part
 * of unmounting process).
 *
 * Note: The acute reader will notice that there is no "rmmod zcache" case.
 * This is b/c the functionality for that is not yet implemented and when
 * done, will require some extra locking not yet devised.
 */

/*
 * Register operations for cleancache. Returns 0 on success.
 */
int cleancache_register_ops(struct cleancache_ops *ops)
{
	int i;

	mutex_lock(&poolid_mutex);
	if (cleancache_ops) {
		mutex_unlock(&poolid_mutex);
		return -EBUSY;
	}
	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
		if (fs_poolid_map[i] == FS_NO_BACKEND)
			fs_poolid_map[i] = ops->init_fs(PAGE_SIZE);
		if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
			shared_fs_poolid_map[i] = ops->init_shared_fs
					(uuids[i], PAGE_SIZE);
	}
	/*
	 * We MUST set cleancache_ops _after_ we have called the backends
	 * init_fs or init_shared_fs functions. Otherwise the compiler might
	 * re-order where cleancache_ops is set in this function.
	 */
	barrier();
	cleancache_ops = ops;
	mutex_unlock(&poolid_mutex);
	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 i;

	mutex_lock(&poolid_mutex);
	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
		if (fs_poolid_map[i] == FS_UNKNOWN) {
			sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
			if (cleancache_ops)
				fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE);
			else
				fs_poolid_map[i] = FS_NO_BACKEND;
			break;
		}
	}
	mutex_unlock(&poolid_mutex);
}
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 i;

	mutex_lock(&poolid_mutex);
	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
		if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
			sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
			uuids[i] = sb->s_uuid;
			if (cleancache_ops)
				shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs
						(sb->s_uuid, PAGE_SIZE);
			else
				shared_fs_poolid_map[i] = FS_NO_BACKEND;
			break;
		}
	}
	mutex_unlock(&poolid_mutex);
}
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;
}

/*
 * Returns a pool_id that is associated with a given fake poolid.
 */
static int get_poolid_from_fake(int fake_pool_id)
{
	if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET)
		return shared_fs_poolid_map[fake_pool_id -
			FAKE_SHARED_FS_POOLID_OFFSET];
	else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET)
		return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET];
	return FS_NO_BACKEND;
}

/*
 * "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;
	int fake_pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };

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

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

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

	if (pool_id >= 0)
		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;
	int fake_pool_id;
	struct cleancache_filekey key = { .u.key = { 0 } };

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

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
	if (fake_pool_id < 0)
		return;

	pool_id = get_poolid_from_fake(fake_pool_id);

	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;
	int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops)
		return;

	if (fake_pool_id >= 0) {
		pool_id = get_poolid_from_fake(fake_pool_id);
		if (pool_id < 0)
			return;

		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;
	int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
	struct cleancache_filekey key = { .u.key = { 0 } };

	if (!cleancache_ops)
		return;

	if (fake_pool_id < 0)
		return;

	pool_id = get_poolid_from_fake(fake_pool_id);

	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 index;
	int fake_pool_id = sb->cleancache_poolid;
	int old_poolid = fake_pool_id;

	mutex_lock(&poolid_mutex);
	if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) {
		index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET;
		old_poolid = shared_fs_poolid_map[index];
		shared_fs_poolid_map[index] = FS_UNKNOWN;
		uuids[index] = NULL;
	} else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) {
		index = fake_pool_id - FAKE_FS_POOLID_OFFSET;
		old_poolid = fs_poolid_map[index];
		fs_poolid_map[index] = FS_UNKNOWN;
	}
	sb->cleancache_poolid = -1;
	if (cleancache_ops)
		cleancache_ops->invalidate_fs(old_poolid);
	mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);

static int __init init_cleancache(void)
{
	int i;

#ifdef CONFIG_DEBUG_FS
	struct dentry *root = debugfs_create_dir("cleancache", NULL);
	if (root == NULL)
		return -ENXIO;
	debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
	debugfs_create_u64("failed_gets", S_IRUGO,
				root, &cleancache_failed_gets);
	debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
	debugfs_create_u64("invalidates", S_IRUGO,
				root, &cleancache_invalidates);
#endif
	for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
		fs_poolid_map[i] = FS_UNKNOWN;
		shared_fs_poolid_map[i] = FS_UNKNOWN;
	}
	return 0;
}
module_init(init_cleancache)