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Dan Streetmanaf8d4172014-08-06 16:08:36 -07001/*
2 * zpool memory storage api
3 *
4 * Copyright (C) 2014 Dan Streetman
5 *
6 * This is a common frontend for memory storage pool implementations.
7 * Typically, this is used to store compressed memory.
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/list.h>
13#include <linux/types.h>
14#include <linux/mm.h>
15#include <linux/slab.h>
16#include <linux/spinlock.h>
17#include <linux/module.h>
18#include <linux/zpool.h>
19
20struct zpool {
Dan Streetmanaf8d4172014-08-06 16:08:36 -070021 struct zpool_driver *driver;
22 void *pool;
Krzysztof Kozlowski78672772015-09-08 15:05:03 -070023 const struct zpool_ops *ops;
Dan Streetmanaf8d4172014-08-06 16:08:36 -070024
25 struct list_head list;
26};
27
28static LIST_HEAD(drivers_head);
29static DEFINE_SPINLOCK(drivers_lock);
30
31static LIST_HEAD(pools_head);
32static DEFINE_SPINLOCK(pools_lock);
33
34/**
35 * zpool_register_driver() - register a zpool implementation.
36 * @driver: driver to register
37 */
38void zpool_register_driver(struct zpool_driver *driver)
39{
40 spin_lock(&drivers_lock);
41 atomic_set(&driver->refcount, 0);
42 list_add(&driver->list, &drivers_head);
43 spin_unlock(&drivers_lock);
44}
45EXPORT_SYMBOL(zpool_register_driver);
46
47/**
48 * zpool_unregister_driver() - unregister a zpool implementation.
49 * @driver: driver to unregister.
50 *
51 * Module usage counting is used to prevent using a driver
52 * while/after unloading, so if this is called from module
53 * exit function, this should never fail; if called from
54 * other than the module exit function, and this returns
55 * failure, the driver is in use and must remain available.
56 */
57int zpool_unregister_driver(struct zpool_driver *driver)
58{
59 int ret = 0, refcount;
60
61 spin_lock(&drivers_lock);
62 refcount = atomic_read(&driver->refcount);
63 WARN_ON(refcount < 0);
64 if (refcount > 0)
65 ret = -EBUSY;
66 else
67 list_del(&driver->list);
68 spin_unlock(&drivers_lock);
69
70 return ret;
71}
72EXPORT_SYMBOL(zpool_unregister_driver);
73
Dan Streetman69e18f42015-11-06 16:29:18 -080074/* this assumes @type is null-terminated. */
Sergey SENOZHATSKY6f3526d2015-11-06 16:29:21 -080075static struct zpool_driver *zpool_get_driver(const char *type)
Dan Streetmanaf8d4172014-08-06 16:08:36 -070076{
77 struct zpool_driver *driver;
78
79 spin_lock(&drivers_lock);
80 list_for_each_entry(driver, &drivers_head, list) {
81 if (!strcmp(driver->type, type)) {
82 bool got = try_module_get(driver->owner);
83
84 if (got)
85 atomic_inc(&driver->refcount);
86 spin_unlock(&drivers_lock);
87 return got ? driver : NULL;
88 }
89 }
90
91 spin_unlock(&drivers_lock);
92 return NULL;
93}
94
95static void zpool_put_driver(struct zpool_driver *driver)
96{
97 atomic_dec(&driver->refcount);
98 module_put(driver->owner);
99}
100
101/**
Dan Streetman3f0e1312015-09-09 15:35:16 -0700102 * zpool_has_pool() - Check if the pool driver is available
103 * @type The type of the zpool to check (e.g. zbud, zsmalloc)
104 *
105 * This checks if the @type pool driver is available. This will try to load
106 * the requested module, if needed, but there is no guarantee the module will
107 * still be loaded and available immediately after calling. If this returns
108 * true, the caller should assume the pool is available, but must be prepared
109 * to handle the @zpool_create_pool() returning failure. However if this
110 * returns false, the caller should assume the requested pool type is not
111 * available; either the requested pool type module does not exist, or could
112 * not be loaded, and calling @zpool_create_pool() with the pool type will
113 * fail.
114 *
Dan Streetman69e18f42015-11-06 16:29:18 -0800115 * The @type string must be null-terminated.
116 *
Dan Streetman3f0e1312015-09-09 15:35:16 -0700117 * Returns: true if @type pool is available, false if not
118 */
119bool zpool_has_pool(char *type)
120{
121 struct zpool_driver *driver = zpool_get_driver(type);
122
123 if (!driver) {
124 request_module("zpool-%s", type);
125 driver = zpool_get_driver(type);
126 }
127
128 if (!driver)
129 return false;
130
131 zpool_put_driver(driver);
132 return true;
133}
134EXPORT_SYMBOL(zpool_has_pool);
135
136/**
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700137 * zpool_create_pool() - Create a new zpool
138 * @type The type of the zpool to create (e.g. zbud, zsmalloc)
Ganesh Mahendran3eba0c62015-02-12 15:00:51 -0800139 * @name The name of the zpool (e.g. zram0, zswap)
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700140 * @gfp The GFP flags to use when allocating the pool.
141 * @ops The optional ops callback.
142 *
143 * This creates a new zpool of the specified type. The gfp flags will be
144 * used when allocating memory, if the implementation supports it. If the
145 * ops param is NULL, then the created zpool will not be shrinkable.
146 *
147 * Implementations must guarantee this to be thread-safe.
148 *
Dan Streetman69e18f42015-11-06 16:29:18 -0800149 * The @type and @name strings must be null-terminated.
150 *
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700151 * Returns: New zpool on success, NULL on failure.
152 */
Sergey SENOZHATSKY6f3526d2015-11-06 16:29:21 -0800153struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
Krzysztof Kozlowski78672772015-09-08 15:05:03 -0700154 const struct zpool_ops *ops)
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700155{
156 struct zpool_driver *driver;
157 struct zpool *zpool;
158
Dan Streetmancf41f5f2015-06-25 15:00:37 -0700159 pr_debug("creating pool type %s\n", type);
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700160
161 driver = zpool_get_driver(type);
162
163 if (!driver) {
Kees Cook137f8cf2014-08-29 15:18:40 -0700164 request_module("zpool-%s", type);
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700165 driver = zpool_get_driver(type);
166 }
167
168 if (!driver) {
169 pr_err("no driver for type %s\n", type);
170 return NULL;
171 }
172
173 zpool = kmalloc(sizeof(*zpool), gfp);
174 if (!zpool) {
175 pr_err("couldn't create zpool - out of memory\n");
176 zpool_put_driver(driver);
177 return NULL;
178 }
179
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700180 zpool->driver = driver;
Dan Streetman479305f2015-06-25 15:00:40 -0700181 zpool->pool = driver->create(name, gfp, ops, zpool);
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700182 zpool->ops = ops;
183
184 if (!zpool->pool) {
185 pr_err("couldn't create %s pool\n", type);
186 zpool_put_driver(driver);
187 kfree(zpool);
188 return NULL;
189 }
190
Dan Streetmancf41f5f2015-06-25 15:00:37 -0700191 pr_debug("created pool type %s\n", type);
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700192
193 spin_lock(&pools_lock);
194 list_add(&zpool->list, &pools_head);
195 spin_unlock(&pools_lock);
196
197 return zpool;
198}
199
200/**
201 * zpool_destroy_pool() - Destroy a zpool
202 * @pool The zpool to destroy.
203 *
204 * Implementations must guarantee this to be thread-safe,
205 * however only when destroying different pools. The same
206 * pool should only be destroyed once, and should not be used
207 * after it is destroyed.
208 *
209 * This destroys an existing zpool. The zpool should not be in use.
210 */
211void zpool_destroy_pool(struct zpool *zpool)
212{
Dan Streetman69e18f42015-11-06 16:29:18 -0800213 pr_debug("destroying pool type %s\n", zpool->driver->type);
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700214
215 spin_lock(&pools_lock);
216 list_del(&zpool->list);
217 spin_unlock(&pools_lock);
218 zpool->driver->destroy(zpool->pool);
219 zpool_put_driver(zpool->driver);
220 kfree(zpool);
221}
222
223/**
224 * zpool_get_type() - Get the type of the zpool
225 * @pool The zpool to check
226 *
227 * This returns the type of the pool.
228 *
229 * Implementations must guarantee this to be thread-safe.
230 *
231 * Returns: The type of zpool.
232 */
Dan Streetman69e18f42015-11-06 16:29:18 -0800233const char *zpool_get_type(struct zpool *zpool)
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700234{
Dan Streetman69e18f42015-11-06 16:29:18 -0800235 return zpool->driver->type;
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700236}
237
238/**
239 * zpool_malloc() - Allocate memory
240 * @pool The zpool to allocate from.
241 * @size The amount of memory to allocate.
242 * @gfp The GFP flags to use when allocating memory.
243 * @handle Pointer to the handle to set
244 *
245 * This allocates the requested amount of memory from the pool.
246 * The gfp flags will be used when allocating memory, if the
247 * implementation supports it. The provided @handle will be
248 * set to the allocated object handle.
249 *
250 * Implementations must guarantee this to be thread-safe.
251 *
252 * Returns: 0 on success, negative value on error.
253 */
254int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
255 unsigned long *handle)
256{
257 return zpool->driver->malloc(zpool->pool, size, gfp, handle);
258}
259
260/**
261 * zpool_free() - Free previously allocated memory
262 * @pool The zpool that allocated the memory.
263 * @handle The handle to the memory to free.
264 *
265 * This frees previously allocated memory. This does not guarantee
266 * that the pool will actually free memory, only that the memory
267 * in the pool will become available for use by the pool.
268 *
269 * Implementations must guarantee this to be thread-safe,
270 * however only when freeing different handles. The same
271 * handle should only be freed once, and should not be used
272 * after freeing.
273 */
274void zpool_free(struct zpool *zpool, unsigned long handle)
275{
276 zpool->driver->free(zpool->pool, handle);
277}
278
279/**
280 * zpool_shrink() - Shrink the pool size
281 * @pool The zpool to shrink.
282 * @pages The number of pages to shrink the pool.
283 * @reclaimed The number of pages successfully evicted.
284 *
285 * This attempts to shrink the actual memory size of the pool
286 * by evicting currently used handle(s). If the pool was
287 * created with no zpool_ops, or the evict call fails for any
288 * of the handles, this will fail. If non-NULL, the @reclaimed
289 * parameter will be set to the number of pages reclaimed,
290 * which may be more than the number of pages requested.
291 *
292 * Implementations must guarantee this to be thread-safe.
293 *
294 * Returns: 0 on success, negative value on error/failure.
295 */
296int zpool_shrink(struct zpool *zpool, unsigned int pages,
297 unsigned int *reclaimed)
298{
299 return zpool->driver->shrink(zpool->pool, pages, reclaimed);
300}
301
302/**
303 * zpool_map_handle() - Map a previously allocated handle into memory
304 * @pool The zpool that the handle was allocated from
305 * @handle The handle to map
306 * @mm How the memory should be mapped
307 *
308 * This maps a previously allocated handle into memory. The @mm
309 * param indicates to the implementation how the memory will be
310 * used, i.e. read-only, write-only, read-write. If the
311 * implementation does not support it, the memory will be treated
312 * as read-write.
313 *
314 * This may hold locks, disable interrupts, and/or preemption,
315 * and the zpool_unmap_handle() must be called to undo those
316 * actions. The code that uses the mapped handle should complete
317 * its operatons on the mapped handle memory quickly and unmap
318 * as soon as possible. As the implementation may use per-cpu
319 * data, multiple handles should not be mapped concurrently on
320 * any cpu.
321 *
322 * Returns: A pointer to the handle's mapped memory area.
323 */
324void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
325 enum zpool_mapmode mapmode)
326{
327 return zpool->driver->map(zpool->pool, handle, mapmode);
328}
329
330/**
331 * zpool_unmap_handle() - Unmap a previously mapped handle
332 * @pool The zpool that the handle was allocated from
333 * @handle The handle to unmap
334 *
335 * This unmaps a previously mapped handle. Any locks or other
336 * actions that the implementation took in zpool_map_handle()
337 * will be undone here. The memory area returned from
338 * zpool_map_handle() should no longer be used after this.
339 */
340void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
341{
342 zpool->driver->unmap(zpool->pool, handle);
343}
344
345/**
346 * zpool_get_total_size() - The total size of the pool
347 * @pool The zpool to check
348 *
349 * This returns the total size in bytes of the pool.
350 *
351 * Returns: Total size of the zpool in bytes.
352 */
353u64 zpool_get_total_size(struct zpool *zpool)
354{
355 return zpool->driver->total_size(zpool->pool);
356}
357
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700358MODULE_LICENSE("GPL");
359MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
360MODULE_DESCRIPTION("Common API for compressed memory storage");