aboutsummaryrefslogtreecommitdiff
path: root/mm/zpool.c
blob: 3744a2d1a624665ae4eab5dfad43f062b30da7c2 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * zpool memory storage api
 *
 * Copyright (C) 2014 Dan Streetman
 *
 * This is a common frontend for memory storage pool implementations.
 * Typically, this is used to store compressed memory.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/list.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/zpool.h>

struct zpool {
	struct zpool_driver *driver;
	void *pool;
	const struct zpool_ops *ops;
	bool evictable;

	struct list_head list;
};

static LIST_HEAD(drivers_head);
static DEFINE_SPINLOCK(drivers_lock);

static LIST_HEAD(pools_head);
static DEFINE_SPINLOCK(pools_lock);

/**
 * zpool_register_driver() - register a zpool implementation.
 * @driver:	driver to register
 */
void zpool_register_driver(struct zpool_driver *driver)
{
	spin_lock(&drivers_lock);
	atomic_set(&driver->refcount, 0);
	list_add(&driver->list, &drivers_head);
	spin_unlock(&drivers_lock);
}
EXPORT_SYMBOL(zpool_register_driver);

/**
 * zpool_unregister_driver() - unregister a zpool implementation.
 * @driver:	driver to unregister.
 *
 * Module usage counting is used to prevent using a driver
 * while/after unloading, so if this is called from module
 * exit function, this should never fail; if called from
 * other than the module exit function, and this returns
 * failure, the driver is in use and must remain available.
 */
int zpool_unregister_driver(struct zpool_driver *driver)
{
	int ret = 0, refcount;

	spin_lock(&drivers_lock);
	refcount = atomic_read(&driver->refcount);
	WARN_ON(refcount < 0);
	if (refcount > 0)
		ret = -EBUSY;
	else
		list_del(&driver->list);
	spin_unlock(&drivers_lock);

	return ret;
}
EXPORT_SYMBOL(zpool_unregister_driver);

/* this assumes @type is null-terminated. */
static struct zpool_driver *zpool_get_driver(const char *type)
{
	struct zpool_driver *driver;

	spin_lock(&drivers_lock);
	list_for_each_entry(driver, &drivers_head, list) {
		if (!strcmp(driver->type, type)) {
			bool got = try_module_get(driver->owner);

			if (got)
				atomic_inc(&driver->refcount);
			spin_unlock(&drivers_lock);
			return got ? driver : NULL;
		}
	}

	spin_unlock(&drivers_lock);
	return NULL;
}

static void zpool_put_driver(struct zpool_driver *driver)
{
	atomic_dec(&driver->refcount);
	module_put(driver->owner);
}

/**
 * zpool_has_pool() - Check if the pool driver is available
 * @type:	The type of the zpool to check (e.g. zbud, zsmalloc)
 *
 * This checks if the @type pool driver is available.  This will try to load
 * the requested module, if needed, but there is no guarantee the module will
 * still be loaded and available immediately after calling.  If this returns
 * true, the caller should assume the pool is available, but must be prepared
 * to handle the @zpool_create_pool() returning failure.  However if this
 * returns false, the caller should assume the requested pool type is not
 * available; either the requested pool type module does not exist, or could
 * not be loaded, and calling @zpool_create_pool() with the pool type will
 * fail.
 *
 * The @type string must be null-terminated.
 *
 * Returns: true if @type pool is available, false if not
 */
bool zpool_has_pool(char *type)
{
	struct zpool_driver *driver = zpool_get_driver(type);

	if (!driver) {
		request_module("zpool-%s", type);
		driver = zpool_get_driver(type);
	}

	if (!driver)
		return false;

	zpool_put_driver(driver);
	return true;
}
EXPORT_SYMBOL(zpool_has_pool);

/**
 * zpool_create_pool() - Create a new zpool
 * @type:	The type of the zpool to create (e.g. zbud, zsmalloc)
 * @name:	The name of the zpool (e.g. zram0, zswap)
 * @gfp:	The GFP flags to use when allocating the pool.
 * @ops:	The optional ops callback.
 *
 * This creates a new zpool of the specified type.  The gfp flags will be
 * used when allocating memory, if the implementation supports it.  If the
 * ops param is NULL, then the created zpool will not be evictable.
 *
 * Implementations must guarantee this to be thread-safe.
 *
 * The @type and @name strings must be null-terminated.
 *
 * Returns: New zpool on success, NULL on failure.
 */
struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
		const struct zpool_ops *ops)
{
	struct zpool_driver *driver;
	struct zpool *zpool;

	pr_debug("creating pool type %s\n", type);

	driver = zpool_get_driver(type);

	if (!driver) {
		request_module("zpool-%s", type);
		driver = zpool_get_driver(type);
	}

	if (!driver) {
		pr_err("no driver for type %s\n", type);
		return NULL;
	}

	zpool = kmalloc(sizeof(*zpool), gfp);
	if (!zpool) {
		pr_err("couldn't create zpool - out of memory\n");
		zpool_put_driver(driver);
		return NULL;
	}

	zpool->driver = driver;
	zpool->pool = driver->create(name, gfp, ops, zpool);
	zpool->ops = ops;
	zpool->evictable = driver->shrink && ops && ops->evict;

	if (!zpool->pool) {
		pr_err("couldn't create %s pool\n", type);
		zpool_put_driver(driver);
		kfree(zpool);
		return NULL;
	}

	pr_debug("created pool type %s\n", type);

	spin_lock(&pools_lock);
	list_add(&zpool->list, &pools_head);
	spin_unlock(&pools_lock);

	return zpool;
}

/**
 * zpool_destroy_pool() - Destroy a zpool
 * @zpool:	The zpool to destroy.
 *
 * Implementations must guarantee this to be thread-safe,
 * however only when destroying different pools.  The same
 * pool should only be destroyed once, and should not be used
 * after it is destroyed.
 *
 * This destroys an existing zpool.  The zpool should not be in use.
 */
void zpool_destroy_pool(struct zpool *zpool)
{
	pr_debug("destroying pool type %s\n", zpool->driver->type);

	spin_lock(&pools_lock);
	list_del(&zpool->list);
	spin_unlock(&pools_lock);
	zpool->driver->destroy(zpool->pool);
	zpool_put_driver(zpool->driver);
	kfree(zpool);
}

/**
 * zpool_get_type() - Get the type of the zpool
 * @zpool:	The zpool to check
 *
 * This returns the type of the pool.
 *
 * Implementations must guarantee this to be thread-safe.
 *
 * Returns: The type of zpool.
 */
const char *zpool_get_type(struct zpool *zpool)
{
	return zpool->driver->type;
}

/**
 * zpool_malloc_support_movable() - Check if the zpool supports
 *	allocating movable memory
 * @zpool:	The zpool to check
 *
 * This returns if the zpool supports allocating movable memory.
 *
 * Implementations must guarantee this to be thread-safe.
 *
 * Returns: true if the zpool supports allocating movable memory, false if not
 */
bool zpool_malloc_support_movable(struct zpool *zpool)
{
	return zpool->driver->malloc_support_movable;
}

/**
 * zpool_malloc() - Allocate memory
 * @zpool:	The zpool to allocate from.
 * @size:	The amount of memory to allocate.
 * @gfp:	The GFP flags to use when allocating memory.
 * @handle:	Pointer to the handle to set
 *
 * This allocates the requested amount of memory from the pool.
 * The gfp flags will be used when allocating memory, if the
 * implementation supports it.  The provided @handle will be
 * set to the allocated object handle.
 *
 * Implementations must guarantee this to be thread-safe.
 *
 * Returns: 0 on success, negative value on error.
 */
int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
			unsigned long *handle)
{
	return zpool->driver->malloc(zpool->pool, size, gfp, handle);
}

/**
 * zpool_free() - Free previously allocated memory
 * @zpool:	The zpool that allocated the memory.
 * @handle:	The handle to the memory to free.
 *
 * This frees previously allocated memory.  This does not guarantee
 * that the pool will actually free memory, only that the memory
 * in the pool will become available for use by the pool.
 *
 * Implementations must guarantee this to be thread-safe,
 * however only when freeing different handles.  The same
 * handle should only be freed once, and should not be used
 * after freeing.
 */
void zpool_free(struct zpool *zpool, unsigned long handle)
{
	zpool->driver->free(zpool->pool, handle);
}

/**
 * zpool_shrink() - Shrink the pool size
 * @zpool:	The zpool to shrink.
 * @pages:	The number of pages to shrink the pool.
 * @reclaimed:	The number of pages successfully evicted.
 *
 * This attempts to shrink the actual memory size of the pool
 * by evicting currently used handle(s).  If the pool was
 * created with no zpool_ops, or the evict call fails for any
 * of the handles, this will fail.  If non-NULL, the @reclaimed
 * parameter will be set to the number of pages reclaimed,
 * which may be more than the number of pages requested.
 *
 * Implementations must guarantee this to be thread-safe.
 *
 * Returns: 0 on success, negative value on error/failure.
 */
int zpool_shrink(struct zpool *zpool, unsigned int pages,
			unsigned int *reclaimed)
{
	return zpool->driver->shrink ?
	       zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
}

/**
 * zpool_map_handle() - Map a previously allocated handle into memory
 * @zpool:	The zpool that the handle was allocated from
 * @handle:	The handle to map
 * @mapmode:	How the memory should be mapped
 *
 * This maps a previously allocated handle into memory.  The @mapmode
 * param indicates to the implementation how the memory will be
 * used, i.e. read-only, write-only, read-write.  If the
 * implementation does not support it, the memory will be treated
 * as read-write.
 *
 * This may hold locks, disable interrupts, and/or preemption,
 * and the zpool_unmap_handle() must be called to undo those
 * actions.  The code that uses the mapped handle should complete
 * its operatons on the mapped handle memory quickly and unmap
 * as soon as possible.  As the implementation may use per-cpu
 * data, multiple handles should not be mapped concurrently on
 * any cpu.
 *
 * Returns: A pointer to the handle's mapped memory area.
 */
void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
			enum zpool_mapmode mapmode)
{
	return zpool->driver->map(zpool->pool, handle, mapmode);
}

/**
 * zpool_unmap_handle() - Unmap a previously mapped handle
 * @zpool:	The zpool that the handle was allocated from
 * @handle:	The handle to unmap
 *
 * This unmaps a previously mapped handle.  Any locks or other
 * actions that the implementation took in zpool_map_handle()
 * will be undone here.  The memory area returned from
 * zpool_map_handle() should no longer be used after this.
 */
void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
{
	zpool->driver->unmap(zpool->pool, handle);
}

/**
 * zpool_get_total_size() - The total size of the pool
 * @zpool:	The zpool to check
 *
 * This returns the total size in bytes of the pool.
 *
 * Returns: Total size of the zpool in bytes.
 */
u64 zpool_get_total_size(struct zpool *zpool)
{
	return zpool->driver->total_size(zpool->pool);
}

/**
 * zpool_evictable() - Test if zpool is potentially evictable
 * @zpool:	The zpool to test
 *
 * Zpool is only potentially evictable when it's created with struct
 * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
 *
 * However, it doesn't necessarily mean driver will use zpool_ops.evict
 * in its implementation of zpool_driver.shrink. It could do internal
 * defragmentation instead.
 *
 * Returns: true if potentially evictable; false otherwise.
 */
bool zpool_evictable(struct zpool *zpool)
{
	return zpool->evictable;
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
MODULE_DESCRIPTION("Common API for compressed memory storage");