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 | |
21 | struct zpool { |
22 | struct zpool_driver *driver; |
23 | void *pool; |
24 | }; |
25 | |
26 | static LIST_HEAD(drivers_head); |
27 | static DEFINE_SPINLOCK(drivers_lock); |
28 | |
29 | /** |
30 | * zpool_register_driver() - register a zpool implementation. |
31 | * @driver: driver to register |
32 | */ |
33 | void zpool_register_driver(struct zpool_driver *driver) |
34 | { |
35 | spin_lock(lock: &drivers_lock); |
36 | atomic_set(v: &driver->refcount, i: 0); |
37 | list_add(new: &driver->list, head: &drivers_head); |
38 | spin_unlock(lock: &drivers_lock); |
39 | } |
40 | EXPORT_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 | */ |
52 | int zpool_unregister_driver(struct zpool_driver *driver) |
53 | { |
54 | int ret = 0, refcount; |
55 | |
56 | spin_lock(lock: &drivers_lock); |
57 | refcount = atomic_read(v: &driver->refcount); |
58 | WARN_ON(refcount < 0); |
59 | if (refcount > 0) |
60 | ret = -EBUSY; |
61 | else |
62 | list_del(entry: &driver->list); |
63 | spin_unlock(lock: &drivers_lock); |
64 | |
65 | return ret; |
66 | } |
67 | EXPORT_SYMBOL(zpool_unregister_driver); |
68 | |
69 | /* this assumes @type is null-terminated. */ |
70 | static struct zpool_driver *zpool_get_driver(const char *type) |
71 | { |
72 | struct zpool_driver *driver; |
73 | |
74 | spin_lock(lock: &drivers_lock); |
75 | list_for_each_entry(driver, &drivers_head, list) { |
76 | if (!strcmp(driver->type, type)) { |
77 | bool got = try_module_get(module: driver->owner); |
78 | |
79 | if (got) |
80 | atomic_inc(v: &driver->refcount); |
81 | spin_unlock(lock: &drivers_lock); |
82 | return got ? driver : NULL; |
83 | } |
84 | } |
85 | |
86 | spin_unlock(lock: &drivers_lock); |
87 | return NULL; |
88 | } |
89 | |
90 | static void zpool_put_driver(struct zpool_driver *driver) |
91 | { |
92 | atomic_dec(v: &driver->refcount); |
93 | module_put(module: 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 | */ |
114 | bool 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 | } |
129 | EXPORT_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 | */ |
147 | struct 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(size: sizeof(*zpool), flags: 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(objp: 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 | */ |
199 | void 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(driver: zpool->driver); |
205 | kfree(objp: 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 | */ |
218 | const 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 | */ |
234 | bool 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 | */ |
255 | int 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 | */ |
275 | void 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 | */ |
302 | void *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 | */ |
318 | void 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 | */ |
331 | u64 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 | */ |
349 | bool zpool_can_sleep_mapped(struct zpool *zpool) |
350 | { |
351 | return zpool->driver->sleep_mapped; |
352 | } |
353 | |
354 | MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>" ); |
355 | MODULE_DESCRIPTION("Common API for compressed memory storage" ); |
356 | |