1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * zpool memory storage api
4 *
5 * Copyright (C) 2014 Dan Streetman
6 *
7 * This is a common frontend for memory storage pool implementations.
8 * Typically, this is used to store compressed memory.
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/list.h>
14#include <linux/types.h>
15#include <linux/mm.h>
16#include <linux/slab.h>
17#include <linux/spinlock.h>
18#include <linux/module.h>
19#include <linux/zpool.h>
20
21struct zpool {
22	struct zpool_driver *driver;
23	void *pool;
24};
25
26static LIST_HEAD(drivers_head);
27static DEFINE_SPINLOCK(drivers_lock);
28
29/**
30 * zpool_register_driver() - register a zpool implementation.
31 * @driver:	driver to register
32 */
33void zpool_register_driver(struct zpool_driver *driver)
34{
35	spin_lock(&drivers_lock);
36	atomic_set(&driver->refcount, 0);
37	list_add(&driver->list, &drivers_head);
38	spin_unlock(&drivers_lock);
39}
40EXPORT_SYMBOL(zpool_register_driver);
41
42/**
43 * zpool_unregister_driver() - unregister a zpool implementation.
44 * @driver:	driver to unregister.
45 *
46 * Module usage counting is used to prevent using a driver
47 * while/after unloading, so if this is called from module
48 * exit function, this should never fail; if called from
49 * other than the module exit function, and this returns
50 * failure, the driver is in use and must remain available.
51 */
52int zpool_unregister_driver(struct zpool_driver *driver)
53{
54	int ret = 0, refcount;
55
56	spin_lock(&drivers_lock);
57	refcount = atomic_read(&driver->refcount);
58	WARN_ON(refcount < 0);
59	if (refcount > 0)
60		ret = -EBUSY;
61	else
62		list_del(&driver->list);
63	spin_unlock(&drivers_lock);
64
65	return ret;
66}
67EXPORT_SYMBOL(zpool_unregister_driver);
68
69/* this assumes @type is null-terminated. */
70static struct zpool_driver *zpool_get_driver(const char *type)
71{
72	struct zpool_driver *driver;
73
74	spin_lock(&drivers_lock);
75	list_for_each_entry(driver, &drivers_head, list) {
76		if (!strcmp(driver->type, type)) {
77			bool got = try_module_get(driver->owner);
78
79			if (got)
80				atomic_inc(&driver->refcount);
81			spin_unlock(&drivers_lock);
82			return got ? driver : NULL;
83		}
84	}
85
86	spin_unlock(&drivers_lock);
87	return NULL;
88}
89
90static void zpool_put_driver(struct zpool_driver *driver)
91{
92	atomic_dec(&driver->refcount);
93	module_put(driver->owner);
94}
95
96/**
97 * zpool_has_pool() - Check if the pool driver is available
98 * @type:	The type of the zpool to check (e.g. zbud, zsmalloc)
99 *
100 * This checks if the @type pool driver is available.  This will try to load
101 * the requested module, if needed, but there is no guarantee the module will
102 * still be loaded and available immediately after calling.  If this returns
103 * true, the caller should assume the pool is available, but must be prepared
104 * to handle the @zpool_create_pool() returning failure.  However if this
105 * returns false, the caller should assume the requested pool type is not
106 * available; either the requested pool type module does not exist, or could
107 * not be loaded, and calling @zpool_create_pool() with the pool type will
108 * fail.
109 *
110 * The @type string must be null-terminated.
111 *
112 * Returns: true if @type pool is available, false if not
113 */
114bool zpool_has_pool(char *type)
115{
116	struct zpool_driver *driver = zpool_get_driver(type);
117
118	if (!driver) {
119		request_module("zpool-%s", type);
120		driver = zpool_get_driver(type);
121	}
122
123	if (!driver)
124		return false;
125
126	zpool_put_driver(driver);
127	return true;
128}
129EXPORT_SYMBOL(zpool_has_pool);
130
131/**
132 * zpool_create_pool() - Create a new zpool
133 * @type:	The type of the zpool to create (e.g. zbud, zsmalloc)
134 * @name:	The name of the zpool (e.g. zram0, zswap)
135 * @gfp:	The GFP flags to use when allocating the pool.
136 *
137 * This creates a new zpool of the specified type.  The gfp flags will be
138 * used when allocating memory, if the implementation supports it.  If the
139 * ops param is NULL, then the created zpool will not be evictable.
140 *
141 * Implementations must guarantee this to be thread-safe.
142 *
143 * The @type and @name strings must be null-terminated.
144 *
145 * Returns: New zpool on success, NULL on failure.
146 */
147struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp)
148{
149	struct zpool_driver *driver;
150	struct zpool *zpool;
151
152	pr_debug("creating pool type %s\n", type);
153
154	driver = zpool_get_driver(type);
155
156	if (!driver) {
157		request_module("zpool-%s", type);
158		driver = zpool_get_driver(type);
159	}
160
161	if (!driver) {
162		pr_err("no driver for type %s\n", type);
163		return NULL;
164	}
165
166	zpool = kmalloc(sizeof(*zpool), gfp);
167	if (!zpool) {
168		pr_err("couldn't create zpool - out of memory\n");
169		zpool_put_driver(driver);
170		return NULL;
171	}
172
173	zpool->driver = driver;
174	zpool->pool = driver->create(name, gfp);
175
176	if (!zpool->pool) {
177		pr_err("couldn't create %s pool\n", type);
178		zpool_put_driver(driver);
179		kfree(zpool);
180		return NULL;
181	}
182
183	pr_debug("created pool type %s\n", type);
184
185	return zpool;
186}
187
188/**
189 * zpool_destroy_pool() - Destroy a zpool
190 * @zpool:	The zpool to destroy.
191 *
192 * Implementations must guarantee this to be thread-safe,
193 * however only when destroying different pools.  The same
194 * pool should only be destroyed once, and should not be used
195 * after it is destroyed.
196 *
197 * This destroys an existing zpool.  The zpool should not be in use.
198 */
199void zpool_destroy_pool(struct zpool *zpool)
200{
201	pr_debug("destroying pool type %s\n", zpool->driver->type);
202
203	zpool->driver->destroy(zpool->pool);
204	zpool_put_driver(zpool->driver);
205	kfree(zpool);
206}
207
208/**
209 * zpool_get_type() - Get the type of the zpool
210 * @zpool:	The zpool to check
211 *
212 * This returns the type of the pool.
213 *
214 * Implementations must guarantee this to be thread-safe.
215 *
216 * Returns: The type of zpool.
217 */
218const char *zpool_get_type(struct zpool *zpool)
219{
220	return zpool->driver->type;
221}
222
223/**
224 * zpool_malloc_support_movable() - Check if the zpool supports
225 *	allocating movable memory
226 * @zpool:	The zpool to check
227 *
228 * This returns if the zpool supports allocating movable memory.
229 *
230 * Implementations must guarantee this to be thread-safe.
231 *
232 * Returns: true if the zpool supports allocating movable memory, false if not
233 */
234bool zpool_malloc_support_movable(struct zpool *zpool)
235{
236	return zpool->driver->malloc_support_movable;
237}
238
239/**
240 * zpool_malloc() - Allocate memory
241 * @zpool:	The zpool to allocate from.
242 * @size:	The amount of memory to allocate.
243 * @gfp:	The GFP flags to use when allocating memory.
244 * @handle:	Pointer to the handle to set
245 *
246 * This allocates the requested amount of memory from the pool.
247 * The gfp flags will be used when allocating memory, if the
248 * implementation supports it.  The provided @handle will be
249 * set to the allocated object handle.
250 *
251 * Implementations must guarantee this to be thread-safe.
252 *
253 * Returns: 0 on success, negative value on error.
254 */
255int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
256			unsigned long *handle)
257{
258	return zpool->driver->malloc(zpool->pool, size, gfp, handle);
259}
260
261/**
262 * zpool_free() - Free previously allocated memory
263 * @zpool:	The zpool that allocated the memory.
264 * @handle:	The handle to the memory to free.
265 *
266 * This frees previously allocated memory.  This does not guarantee
267 * that the pool will actually free memory, only that the memory
268 * in the pool will become available for use by the pool.
269 *
270 * Implementations must guarantee this to be thread-safe,
271 * however only when freeing different handles.  The same
272 * handle should only be freed once, and should not be used
273 * after freeing.
274 */
275void zpool_free(struct zpool *zpool, unsigned long handle)
276{
277	zpool->driver->free(zpool->pool, handle);
278}
279
280/**
281 * zpool_map_handle() - Map a previously allocated handle into memory
282 * @zpool:	The zpool that the handle was allocated from
283 * @handle:	The handle to map
284 * @mapmode:	How the memory should be mapped
285 *
286 * This maps a previously allocated handle into memory.  The @mapmode
287 * param indicates to the implementation how the memory will be
288 * used, i.e. read-only, write-only, read-write.  If the
289 * implementation does not support it, the memory will be treated
290 * as read-write.
291 *
292 * This may hold locks, disable interrupts, and/or preemption,
293 * and the zpool_unmap_handle() must be called to undo those
294 * actions.  The code that uses the mapped handle should complete
295 * its operations on the mapped handle memory quickly and unmap
296 * as soon as possible.  As the implementation may use per-cpu
297 * data, multiple handles should not be mapped concurrently on
298 * any cpu.
299 *
300 * Returns: A pointer to the handle's mapped memory area.
301 */
302void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
303			enum zpool_mapmode mapmode)
304{
305	return zpool->driver->map(zpool->pool, handle, mapmode);
306}
307
308/**
309 * zpool_unmap_handle() - Unmap a previously mapped handle
310 * @zpool:	The zpool that the handle was allocated from
311 * @handle:	The handle to unmap
312 *
313 * This unmaps a previously mapped handle.  Any locks or other
314 * actions that the implementation took in zpool_map_handle()
315 * will be undone here.  The memory area returned from
316 * zpool_map_handle() should no longer be used after this.
317 */
318void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
319{
320	zpool->driver->unmap(zpool->pool, handle);
321}
322
323/**
324 * zpool_get_total_size() - The total size of the pool
325 * @zpool:	The zpool to check
326 *
327 * This returns the total size in bytes of the pool.
328 *
329 * Returns: Total size of the zpool in bytes.
330 */
331u64 zpool_get_total_size(struct zpool *zpool)
332{
333	return zpool->driver->total_size(zpool->pool);
334}
335
336/**
337 * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
338 * @zpool:	The zpool to test
339 *
340 * Some allocators enter non-preemptible context in ->map() callback (e.g.
341 * disable pagefaults) and exit that context in ->unmap(), which limits what
342 * we can do with the mapped object. For instance, we cannot wait for
343 * asynchronous crypto API to decompress such an object or take mutexes
344 * since those will call into the scheduler. This function tells us whether
345 * we use such an allocator.
346 *
347 * Returns: true if zpool can sleep; false otherwise.
348 */
349bool zpool_can_sleep_mapped(struct zpool *zpool)
350{
351	return zpool->driver->sleep_mapped;
352}
353
354MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
355MODULE_DESCRIPTION("Common API for compressed memory storage");
356