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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 * @ops: The optional ops callback.
137 *
138 * This creates a new zpool of the specified type. The gfp flags will be
139 * used when allocating memory, if the implementation supports it. If the
140 * ops param is NULL, then the created zpool will not be evictable.
141 *
142 * Implementations must guarantee this to be thread-safe.
143 *
144 * The @type and @name strings must be null-terminated.
145 *
146 * Returns: New zpool on success, NULL on failure.
147 */
148struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
149 const struct zpool_ops *ops)
150{
151 struct zpool_driver *driver;
152 struct zpool *zpool;
153
154 pr_debug("creating pool type %s\n", type);
155
156 driver = zpool_get_driver(type);
157
158 if (!driver) {
159 request_module("zpool-%s", type);
160 driver = zpool_get_driver(type);
161 }
162
163 if (!driver) {
164 pr_err("no driver for type %s\n", type);
165 return NULL;
166 }
167
168 zpool = kmalloc(sizeof(*zpool), gfp);
169 if (!zpool) {
170 pr_err("couldn't create zpool - out of memory\n");
171 zpool_put_driver(driver);
172 return NULL;
173 }
174
175 zpool->driver = driver;
176 zpool->pool = driver->create(name, gfp, ops, zpool);
177
178 if (!zpool->pool) {
179 pr_err("couldn't create %s pool\n", type);
180 zpool_put_driver(driver);
181 kfree(zpool);
182 return NULL;
183 }
184
185 pr_debug("created pool type %s\n", type);
186
187 return zpool;
188}
189
190/**
191 * zpool_destroy_pool() - Destroy a zpool
192 * @zpool: 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 */
201void zpool_destroy_pool(struct zpool *zpool)
202{
203 pr_debug("destroying pool type %s\n", zpool->driver->type);
204
205 zpool->driver->destroy(zpool->pool);
206 zpool_put_driver(zpool->driver);
207 kfree(zpool);
208}
209
210/**
211 * zpool_get_type() - Get the type of the zpool
212 * @zpool: The zpool to check
213 *
214 * This returns the type of the pool.
215 *
216 * Implementations must guarantee this to be thread-safe.
217 *
218 * Returns: The type of zpool.
219 */
220const char *zpool_get_type(struct zpool *zpool)
221{
222 return zpool->driver->type;
223}
224
225/**
226 * zpool_malloc_support_movable() - Check if the zpool supports
227 * allocating movable memory
228 * @zpool: The zpool to check
229 *
230 * This returns if the zpool supports allocating movable memory.
231 *
232 * Implementations must guarantee this to be thread-safe.
233 *
234 * Returns: true if the zpool supports allocating movable memory, false if not
235 */
236bool zpool_malloc_support_movable(struct zpool *zpool)
237{
238 return zpool->driver->malloc_support_movable;
239}
240
241/**
242 * zpool_malloc() - Allocate memory
243 * @zpool: The zpool to allocate from.
244 * @size: The amount of memory to allocate.
245 * @gfp: The GFP flags to use when allocating memory.
246 * @handle: Pointer to the handle to set
247 *
248 * This allocates the requested amount of memory from the pool.
249 * The gfp flags will be used when allocating memory, if the
250 * implementation supports it. The provided @handle will be
251 * set to the allocated object handle.
252 *
253 * Implementations must guarantee this to be thread-safe.
254 *
255 * Returns: 0 on success, negative value on error.
256 */
257int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
258 unsigned long *handle)
259{
260 return zpool->driver->malloc(zpool->pool, size, gfp, handle);
261}
262
263/**
264 * zpool_free() - Free previously allocated memory
265 * @zpool: The zpool that allocated the memory.
266 * @handle: The handle to the memory to free.
267 *
268 * This frees previously allocated memory. This does not guarantee
269 * that the pool will actually free memory, only that the memory
270 * in the pool will become available for use by the pool.
271 *
272 * Implementations must guarantee this to be thread-safe,
273 * however only when freeing different handles. The same
274 * handle should only be freed once, and should not be used
275 * after freeing.
276 */
277void zpool_free(struct zpool *zpool, unsigned long handle)
278{
279 zpool->driver->free(zpool->pool, handle);
280}
281
282/**
283 * zpool_shrink() - Shrink the pool size
284 * @zpool: The zpool to shrink.
285 * @pages: The number of pages to shrink the pool.
286 * @reclaimed: The number of pages successfully evicted.
287 *
288 * This attempts to shrink the actual memory size of the pool
289 * by evicting currently used handle(s). If the pool was
290 * created with no zpool_ops, or the evict call fails for any
291 * of the handles, this will fail. If non-NULL, the @reclaimed
292 * parameter will be set to the number of pages reclaimed,
293 * which may be more than the number of pages requested.
294 *
295 * Implementations must guarantee this to be thread-safe.
296 *
297 * Returns: 0 on success, negative value on error/failure.
298 */
299int zpool_shrink(struct zpool *zpool, unsigned int pages,
300 unsigned int *reclaimed)
301{
302 return zpool->driver->shrink ?
303 zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
304}
305
306/**
307 * zpool_map_handle() - Map a previously allocated handle into memory
308 * @zpool: The zpool that the handle was allocated from
309 * @handle: The handle to map
310 * @mapmode: How the memory should be mapped
311 *
312 * This maps a previously allocated handle into memory. The @mapmode
313 * param indicates to the implementation how the memory will be
314 * used, i.e. read-only, write-only, read-write. If the
315 * implementation does not support it, the memory will be treated
316 * as read-write.
317 *
318 * This may hold locks, disable interrupts, and/or preemption,
319 * and the zpool_unmap_handle() must be called to undo those
320 * actions. The code that uses the mapped handle should complete
321 * its operations on the mapped handle memory quickly and unmap
322 * as soon as possible. As the implementation may use per-cpu
323 * data, multiple handles should not be mapped concurrently on
324 * any cpu.
325 *
326 * Returns: A pointer to the handle's mapped memory area.
327 */
328void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
329 enum zpool_mapmode mapmode)
330{
331 return zpool->driver->map(zpool->pool, handle, mapmode);
332}
333
334/**
335 * zpool_unmap_handle() - Unmap a previously mapped handle
336 * @zpool: The zpool that the handle was allocated from
337 * @handle: The handle to unmap
338 *
339 * This unmaps a previously mapped handle. Any locks or other
340 * actions that the implementation took in zpool_map_handle()
341 * will be undone here. The memory area returned from
342 * zpool_map_handle() should no longer be used after this.
343 */
344void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
345{
346 zpool->driver->unmap(zpool->pool, handle);
347}
348
349/**
350 * zpool_get_total_size() - The total size of the pool
351 * @zpool: The zpool to check
352 *
353 * This returns the total size in bytes of the pool.
354 *
355 * Returns: Total size of the zpool in bytes.
356 */
357u64 zpool_get_total_size(struct zpool *zpool)
358{
359 return zpool->driver->total_size(zpool->pool);
360}
361
362/**
363 * zpool_evictable() - Test if zpool is potentially evictable
364 * @zpool: The zpool to test
365 *
366 * Zpool is only potentially evictable when it's created with struct
367 * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
368 *
369 * However, it doesn't necessarily mean driver will use zpool_ops.evict
370 * in its implementation of zpool_driver.shrink. It could do internal
371 * defragmentation instead.
372 *
373 * Returns: true if potentially evictable; false otherwise.
374 */
375bool zpool_evictable(struct zpool *zpool)
376{
377 return zpool->driver->shrink;
378}
379
380/**
381 * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
382 * @zpool: The zpool to test
383 *
384 * Some allocators enter non-preemptible context in ->map() callback (e.g.
385 * disable pagefaults) and exit that context in ->unmap(), which limits what
386 * we can do with the mapped object. For instance, we cannot wait for
387 * asynchronous crypto API to decompress such an object or take mutexes
388 * since those will call into the scheduler. This function tells us whether
389 * we use such an allocator.
390 *
391 * Returns: true if zpool can sleep; false otherwise.
392 */
393bool zpool_can_sleep_mapped(struct zpool *zpool)
394{
395 return zpool->driver->sleep_mapped;
396}
397
398MODULE_LICENSE("GPL");
399MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
400MODULE_DESCRIPTION("Common API for compressed memory storage");
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
20struct zpool {
21 struct zpool_driver *driver;
22 void *pool;
23 const struct zpool_ops *ops;
24
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
74/* this assumes @type is null-terminated. */
75static 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
95static 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 */
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/**
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 */
153struct 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 */
211void 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 */
233const 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 */
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
358MODULE_LICENSE("GPL");
359MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
360MODULE_DESCRIPTION("Common API for compressed memory storage");