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1 | /* |
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 | |
20 | struct zpool { |
21 | char *type; |
22 | |
23 | struct zpool_driver *driver; |
24 | void *pool; |
25 | struct zpool_ops *ops; |
26 | |
27 | struct list_head list; |
28 | }; |
29 | |
30 | static LIST_HEAD(drivers_head); |
31 | static DEFINE_SPINLOCK(drivers_lock); |
32 | |
33 | static LIST_HEAD(pools_head); |
34 | static DEFINE_SPINLOCK(pools_lock); |
35 | |
36 | /** |
37 | * zpool_register_driver() - register a zpool implementation. |
38 | * @driver: driver to register |
39 | */ |
40 | void zpool_register_driver(struct zpool_driver *driver) |
41 | { |
42 | spin_lock(&drivers_lock); |
43 | atomic_set(&driver->refcount, 0); |
44 | list_add(&driver->list, &drivers_head); |
45 | spin_unlock(&drivers_lock); |
46 | } |
47 | EXPORT_SYMBOL(zpool_register_driver); |
48 | |
49 | /** |
50 | * zpool_unregister_driver() - unregister a zpool implementation. |
51 | * @driver: driver to unregister. |
52 | * |
53 | * Module usage counting is used to prevent using a driver |
54 | * while/after unloading, so if this is called from module |
55 | * exit function, this should never fail; if called from |
56 | * other than the module exit function, and this returns |
57 | * failure, the driver is in use and must remain available. |
58 | */ |
59 | int zpool_unregister_driver(struct zpool_driver *driver) |
60 | { |
61 | int ret = 0, refcount; |
62 | |
63 | spin_lock(&drivers_lock); |
64 | refcount = atomic_read(&driver->refcount); |
65 | WARN_ON(refcount < 0); |
66 | if (refcount > 0) |
67 | ret = -EBUSY; |
68 | else |
69 | list_del(&driver->list); |
70 | spin_unlock(&drivers_lock); |
71 | |
72 | return ret; |
73 | } |
74 | EXPORT_SYMBOL(zpool_unregister_driver); |
75 | |
76 | /** |
77 | * zpool_evict() - evict callback from a zpool implementation. |
78 | * @pool: pool to evict from. |
79 | * @handle: handle to evict. |
80 | * |
81 | * This can be used by zpool implementations to call the |
82 | * user's evict zpool_ops struct evict callback. |
83 | */ |
84 | int zpool_evict(void *pool, unsigned long handle) |
85 | { |
86 | struct zpool *zpool; |
87 | |
88 | spin_lock(&pools_lock); |
89 | list_for_each_entry(zpool, &pools_head, list) { |
90 | if (zpool->pool == pool) { |
91 | spin_unlock(&pools_lock); |
92 | if (!zpool->ops || !zpool->ops->evict) |
93 | return -EINVAL; |
94 | return zpool->ops->evict(zpool, handle); |
95 | } |
96 | } |
97 | spin_unlock(&pools_lock); |
98 | |
99 | return -ENOENT; |
100 | } |
101 | EXPORT_SYMBOL(zpool_evict); |
102 | |
103 | static struct zpool_driver *zpool_get_driver(char *type) |
104 | { |
105 | struct zpool_driver *driver; |
106 | |
107 | spin_lock(&drivers_lock); |
108 | list_for_each_entry(driver, &drivers_head, list) { |
109 | if (!strcmp(driver->type, type)) { |
110 | bool got = try_module_get(driver->owner); |
111 | |
112 | if (got) |
113 | atomic_inc(&driver->refcount); |
114 | spin_unlock(&drivers_lock); |
115 | return got ? driver : NULL; |
116 | } |
117 | } |
118 | |
119 | spin_unlock(&drivers_lock); |
120 | return NULL; |
121 | } |
122 | |
123 | static void zpool_put_driver(struct zpool_driver *driver) |
124 | { |
125 | atomic_dec(&driver->refcount); |
126 | module_put(driver->owner); |
127 | } |
128 | |
129 | /** |
130 | * zpool_create_pool() - Create a new zpool |
131 | * @type The type of the zpool to create (e.g. zbud, zsmalloc) |
132 | * @gfp The GFP flags to use when allocating the pool. |
133 | * @ops The optional ops callback. |
134 | * |
135 | * This creates a new zpool of the specified type. The gfp flags will be |
136 | * used when allocating memory, if the implementation supports it. If the |
137 | * ops param is NULL, then the created zpool will not be shrinkable. |
138 | * |
139 | * Implementations must guarantee this to be thread-safe. |
140 | * |
141 | * Returns: New zpool on success, NULL on failure. |
142 | */ |
143 | struct zpool *zpool_create_pool(char *type, gfp_t gfp, struct zpool_ops *ops) |
144 | { |
145 | struct zpool_driver *driver; |
146 | struct zpool *zpool; |
147 | |
148 | pr_info("creating pool type %s\n", type); |
149 | |
150 | driver = zpool_get_driver(type); |
151 | |
152 | if (!driver) { |
153 | request_module("zpool-%s", type); |
154 | driver = zpool_get_driver(type); |
155 | } |
156 | |
157 | if (!driver) { |
158 | pr_err("no driver for type %s\n", type); |
159 | return NULL; |
160 | } |
161 | |
162 | zpool = kmalloc(sizeof(*zpool), gfp); |
163 | if (!zpool) { |
164 | pr_err("couldn't create zpool - out of memory\n"); |
165 | zpool_put_driver(driver); |
166 | return NULL; |
167 | } |
168 | |
169 | zpool->type = driver->type; |
170 | zpool->driver = driver; |
171 | zpool->pool = driver->create(gfp, ops); |
172 | zpool->ops = ops; |
173 | |
174 | if (!zpool->pool) { |
175 | pr_err("couldn't create %s pool\n", type); |
176 | zpool_put_driver(driver); |
177 | kfree(zpool); |
178 | return NULL; |
179 | } |
180 | |
181 | pr_info("created %s pool\n", type); |
182 | |
183 | spin_lock(&pools_lock); |
184 | list_add(&zpool->list, &pools_head); |
185 | spin_unlock(&pools_lock); |
186 | |
187 | return zpool; |
188 | } |
189 | |
190 | /** |
191 | * zpool_destroy_pool() - Destroy a zpool |
192 | * @pool The zpool to destroy. |
193 | * |
194 | * Implementations must guarantee this to be thread-safe, |
195 | * however only when destroying different pools. The same |
196 | * pool should only be destroyed once, and should not be used |
197 | * after it is destroyed. |
198 | * |
199 | * This destroys an existing zpool. The zpool should not be in use. |
200 | */ |
201 | void zpool_destroy_pool(struct zpool *zpool) |
202 | { |
203 | pr_info("destroying pool type %s\n", zpool->type); |
204 | |
205 | spin_lock(&pools_lock); |
206 | list_del(&zpool->list); |
207 | spin_unlock(&pools_lock); |
208 | zpool->driver->destroy(zpool->pool); |
209 | zpool_put_driver(zpool->driver); |
210 | kfree(zpool); |
211 | } |
212 | |
213 | /** |
214 | * zpool_get_type() - Get the type of the zpool |
215 | * @pool The zpool to check |
216 | * |
217 | * This returns the type of the pool. |
218 | * |
219 | * Implementations must guarantee this to be thread-safe. |
220 | * |
221 | * Returns: The type of zpool. |
222 | */ |
223 | char *zpool_get_type(struct zpool *zpool) |
224 | { |
225 | return zpool->type; |
226 | } |
227 | |
228 | /** |
229 | * zpool_malloc() - Allocate memory |
230 | * @pool The zpool to allocate from. |
231 | * @size The amount of memory to allocate. |
232 | * @gfp The GFP flags to use when allocating memory. |
233 | * @handle Pointer to the handle to set |
234 | * |
235 | * This allocates the requested amount of memory from the pool. |
236 | * The gfp flags will be used when allocating memory, if the |
237 | * implementation supports it. The provided @handle will be |
238 | * set to the allocated object handle. |
239 | * |
240 | * Implementations must guarantee this to be thread-safe. |
241 | * |
242 | * Returns: 0 on success, negative value on error. |
243 | */ |
244 | int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp, |
245 | unsigned long *handle) |
246 | { |
247 | return zpool->driver->malloc(zpool->pool, size, gfp, handle); |
248 | } |
249 | |
250 | /** |
251 | * zpool_free() - Free previously allocated memory |
252 | * @pool The zpool that allocated the memory. |
253 | * @handle The handle to the memory to free. |
254 | * |
255 | * This frees previously allocated memory. This does not guarantee |
256 | * that the pool will actually free memory, only that the memory |
257 | * in the pool will become available for use by the pool. |
258 | * |
259 | * Implementations must guarantee this to be thread-safe, |
260 | * however only when freeing different handles. The same |
261 | * handle should only be freed once, and should not be used |
262 | * after freeing. |
263 | */ |
264 | void zpool_free(struct zpool *zpool, unsigned long handle) |
265 | { |
266 | zpool->driver->free(zpool->pool, handle); |
267 | } |
268 | |
269 | /** |
270 | * zpool_shrink() - Shrink the pool size |
271 | * @pool The zpool to shrink. |
272 | * @pages The number of pages to shrink the pool. |
273 | * @reclaimed The number of pages successfully evicted. |
274 | * |
275 | * This attempts to shrink the actual memory size of the pool |
276 | * by evicting currently used handle(s). If the pool was |
277 | * created with no zpool_ops, or the evict call fails for any |
278 | * of the handles, this will fail. If non-NULL, the @reclaimed |
279 | * parameter will be set to the number of pages reclaimed, |
280 | * which may be more than the number of pages requested. |
281 | * |
282 | * Implementations must guarantee this to be thread-safe. |
283 | * |
284 | * Returns: 0 on success, negative value on error/failure. |
285 | */ |
286 | int zpool_shrink(struct zpool *zpool, unsigned int pages, |
287 | unsigned int *reclaimed) |
288 | { |
289 | return zpool->driver->shrink(zpool->pool, pages, reclaimed); |
290 | } |
291 | |
292 | /** |
293 | * zpool_map_handle() - Map a previously allocated handle into memory |
294 | * @pool The zpool that the handle was allocated from |
295 | * @handle The handle to map |
296 | * @mm How the memory should be mapped |
297 | * |
298 | * This maps a previously allocated handle into memory. The @mm |
299 | * param indicates to the implementation how the memory will be |
300 | * used, i.e. read-only, write-only, read-write. If the |
301 | * implementation does not support it, the memory will be treated |
302 | * as read-write. |
303 | * |
304 | * This may hold locks, disable interrupts, and/or preemption, |
305 | * and the zpool_unmap_handle() must be called to undo those |
306 | * actions. The code that uses the mapped handle should complete |
307 | * its operatons on the mapped handle memory quickly and unmap |
308 | * as soon as possible. As the implementation may use per-cpu |
309 | * data, multiple handles should not be mapped concurrently on |
310 | * any cpu. |
311 | * |
312 | * Returns: A pointer to the handle's mapped memory area. |
313 | */ |
314 | void *zpool_map_handle(struct zpool *zpool, unsigned long handle, |
315 | enum zpool_mapmode mapmode) |
316 | { |
317 | return zpool->driver->map(zpool->pool, handle, mapmode); |
318 | } |
319 | |
320 | /** |
321 | * zpool_unmap_handle() - Unmap a previously mapped handle |
322 | * @pool The zpool that the handle was allocated from |
323 | * @handle The handle to unmap |
324 | * |
325 | * This unmaps a previously mapped handle. Any locks or other |
326 | * actions that the implementation took in zpool_map_handle() |
327 | * will be undone here. The memory area returned from |
328 | * zpool_map_handle() should no longer be used after this. |
329 | */ |
330 | void zpool_unmap_handle(struct zpool *zpool, unsigned long handle) |
331 | { |
332 | zpool->driver->unmap(zpool->pool, handle); |
333 | } |
334 | |
335 | /** |
336 | * zpool_get_total_size() - The total size of the pool |
337 | * @pool The zpool to check |
338 | * |
339 | * This returns the total size in bytes of the pool. |
340 | * |
341 | * Returns: Total size of the zpool in bytes. |
342 | */ |
343 | u64 zpool_get_total_size(struct zpool *zpool) |
344 | { |
345 | return zpool->driver->total_size(zpool->pool); |
346 | } |
347 | |
348 | static int __init init_zpool(void) |
349 | { |
350 | pr_info("loaded\n"); |
351 | return 0; |
352 | } |
353 | |
354 | static void __exit exit_zpool(void) |
355 | { |
356 | pr_info("unloaded\n"); |
357 | } |
358 | |
359 | module_init(init_zpool); |
360 | module_exit(exit_zpool); |
361 | |
362 | MODULE_LICENSE("GPL"); |
363 | MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>"); |
364 | MODULE_DESCRIPTION("Common API for compressed memory storage"); |
365 |
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