blob: fd3ff719c32cb9cf25dafca9d73f789d8071bad5
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 | struct zpool_driver *driver; |
22 | void *pool; |
23 | const struct zpool_ops *ops; |
24 | |
25 | struct list_head list; |
26 | }; |
27 | |
28 | static LIST_HEAD(drivers_head); |
29 | static DEFINE_SPINLOCK(drivers_lock); |
30 | |
31 | static LIST_HEAD(pools_head); |
32 | static DEFINE_SPINLOCK(pools_lock); |
33 | |
34 | /** |
35 | * zpool_register_driver() - register a zpool implementation. |
36 | * @driver: driver to register |
37 | */ |
38 | void 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 | } |
45 | EXPORT_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 | */ |
57 | int 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 | } |
72 | EXPORT_SYMBOL(zpool_unregister_driver); |
73 | |
74 | /* this assumes @type is null-terminated. */ |
75 | static struct zpool_driver *zpool_get_driver(const char *type) |
76 | { |
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 | |
95 | static void zpool_put_driver(struct zpool_driver *driver) |
96 | { |
97 | atomic_dec(&driver->refcount); |
98 | module_put(driver->owner); |
99 | } |
100 | |
101 | /** |
102 | * 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 | * |
115 | * The @type string must be null-terminated. |
116 | * |
117 | * Returns: true if @type pool is available, false if not |
118 | */ |
119 | bool 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 | } |
134 | EXPORT_SYMBOL(zpool_has_pool); |
135 | |
136 | /** |
137 | * zpool_create_pool() - Create a new zpool |
138 | * @type The type of the zpool to create (e.g. zbud, zsmalloc) |
139 | * @name The name of the zpool (e.g. zram0, zswap) |
140 | * @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 | * |
149 | * The @type and @name strings must be null-terminated. |
150 | * |
151 | * Returns: New zpool on success, NULL on failure. |
152 | */ |
153 | struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp, |
154 | const struct zpool_ops *ops) |
155 | { |
156 | struct zpool_driver *driver; |
157 | struct zpool *zpool; |
158 | |
159 | pr_debug("creating pool type %s\n", type); |
160 | |
161 | driver = zpool_get_driver(type); |
162 | |
163 | if (!driver) { |
164 | request_module("zpool-%s", type); |
165 | 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 | |
180 | zpool->driver = driver; |
181 | zpool->pool = driver->create(name, gfp, ops, zpool); |
182 | 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 | |
191 | pr_debug("created pool type %s\n", type); |
192 | |
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 | */ |
211 | void zpool_destroy_pool(struct zpool *zpool) |
212 | { |
213 | pr_debug("destroying pool type %s\n", zpool->driver->type); |
214 | |
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 | */ |
233 | const char *zpool_get_type(struct zpool *zpool) |
234 | { |
235 | return zpool->driver->type; |
236 | } |
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 | */ |
254 | int 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 | */ |
274 | void 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 | */ |
296 | int 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 | */ |
324 | void *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 | */ |
340 | void 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 | */ |
353 | u64 zpool_get_total_size(struct zpool *zpool) |
354 | { |
355 | return zpool->driver->total_size(zpool->pool); |
356 | } |
357 | |
358 | MODULE_LICENSE("GPL"); |
359 | MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>"); |
360 | MODULE_DESCRIPTION("Common API for compressed memory storage"); |
361 |