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TOMOYO Linux Cross Reference
Linux/mm/zpool.c

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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  * @name        The name of the zpool (e.g. zram0, zswap)
133  * @gfp         The GFP flags to use when allocating the pool.
134  * @ops         The optional ops callback.
135  *
136  * This creates a new zpool of the specified type.  The gfp flags will be
137  * used when allocating memory, if the implementation supports it.  If the
138  * ops param is NULL, then the created zpool will not be shrinkable.
139  *
140  * Implementations must guarantee this to be thread-safe.
141  *
142  * Returns: New zpool on success, NULL on failure.
143  */
144 struct zpool *zpool_create_pool(char *type, char *name, gfp_t gfp,
145                 struct zpool_ops *ops)
146 {
147         struct zpool_driver *driver;
148         struct zpool *zpool;
149 
150         pr_info("creating pool type %s\n", type);
151 
152         driver = zpool_get_driver(type);
153 
154         if (!driver) {
155                 request_module("zpool-%s", type);
156                 driver = zpool_get_driver(type);
157         }
158 
159         if (!driver) {
160                 pr_err("no driver for type %s\n", type);
161                 return NULL;
162         }
163 
164         zpool = kmalloc(sizeof(*zpool), gfp);
165         if (!zpool) {
166                 pr_err("couldn't create zpool - out of memory\n");
167                 zpool_put_driver(driver);
168                 return NULL;
169         }
170 
171         zpool->type = driver->type;
172         zpool->driver = driver;
173         zpool->pool = driver->create(name, gfp, ops);
174         zpool->ops = ops;
175 
176         if (!zpool->pool) {
177                 pr_err("couldn't create %s pool\n", type);
178                 zpool_put_driver(driver);
179                 kfree(zpool);
180                 return NULL;
181         }
182 
183         pr_info("created %s pool\n", type);
184 
185         spin_lock(&pools_lock);
186         list_add(&zpool->list, &pools_head);
187         spin_unlock(&pools_lock);
188 
189         return zpool;
190 }
191 
192 /**
193  * zpool_destroy_pool() - Destroy a zpool
194  * @pool        The zpool to destroy.
195  *
196  * Implementations must guarantee this to be thread-safe,
197  * however only when destroying different pools.  The same
198  * pool should only be destroyed once, and should not be used
199  * after it is destroyed.
200  *
201  * This destroys an existing zpool.  The zpool should not be in use.
202  */
203 void zpool_destroy_pool(struct zpool *zpool)
204 {
205         pr_info("destroying pool type %s\n", zpool->type);
206 
207         spin_lock(&pools_lock);
208         list_del(&zpool->list);
209         spin_unlock(&pools_lock);
210         zpool->driver->destroy(zpool->pool);
211         zpool_put_driver(zpool->driver);
212         kfree(zpool);
213 }
214 
215 /**
216  * zpool_get_type() - Get the type of the zpool
217  * @pool        The zpool to check
218  *
219  * This returns the type of the pool.
220  *
221  * Implementations must guarantee this to be thread-safe.
222  *
223  * Returns: The type of zpool.
224  */
225 char *zpool_get_type(struct zpool *zpool)
226 {
227         return zpool->type;
228 }
229 
230 /**
231  * zpool_malloc() - Allocate memory
232  * @pool        The zpool to allocate from.
233  * @size        The amount of memory to allocate.
234  * @gfp         The GFP flags to use when allocating memory.
235  * @handle      Pointer to the handle to set
236  *
237  * This allocates the requested amount of memory from the pool.
238  * The gfp flags will be used when allocating memory, if the
239  * implementation supports it.  The provided @handle will be
240  * set to the allocated object handle.
241  *
242  * Implementations must guarantee this to be thread-safe.
243  *
244  * Returns: 0 on success, negative value on error.
245  */
246 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
247                         unsigned long *handle)
248 {
249         return zpool->driver->malloc(zpool->pool, size, gfp, handle);
250 }
251 
252 /**
253  * zpool_free() - Free previously allocated memory
254  * @pool        The zpool that allocated the memory.
255  * @handle      The handle to the memory to free.
256  *
257  * This frees previously allocated memory.  This does not guarantee
258  * that the pool will actually free memory, only that the memory
259  * in the pool will become available for use by the pool.
260  *
261  * Implementations must guarantee this to be thread-safe,
262  * however only when freeing different handles.  The same
263  * handle should only be freed once, and should not be used
264  * after freeing.
265  */
266 void zpool_free(struct zpool *zpool, unsigned long handle)
267 {
268         zpool->driver->free(zpool->pool, handle);
269 }
270 
271 /**
272  * zpool_shrink() - Shrink the pool size
273  * @pool        The zpool to shrink.
274  * @pages       The number of pages to shrink the pool.
275  * @reclaimed   The number of pages successfully evicted.
276  *
277  * This attempts to shrink the actual memory size of the pool
278  * by evicting currently used handle(s).  If the pool was
279  * created with no zpool_ops, or the evict call fails for any
280  * of the handles, this will fail.  If non-NULL, the @reclaimed
281  * parameter will be set to the number of pages reclaimed,
282  * which may be more than the number of pages requested.
283  *
284  * Implementations must guarantee this to be thread-safe.
285  *
286  * Returns: 0 on success, negative value on error/failure.
287  */
288 int zpool_shrink(struct zpool *zpool, unsigned int pages,
289                         unsigned int *reclaimed)
290 {
291         return zpool->driver->shrink(zpool->pool, pages, reclaimed);
292 }
293 
294 /**
295  * zpool_map_handle() - Map a previously allocated handle into memory
296  * @pool        The zpool that the handle was allocated from
297  * @handle      The handle to map
298  * @mm          How the memory should be mapped
299  *
300  * This maps a previously allocated handle into memory.  The @mm
301  * param indicates to the implementation how the memory will be
302  * used, i.e. read-only, write-only, read-write.  If the
303  * implementation does not support it, the memory will be treated
304  * as read-write.
305  *
306  * This may hold locks, disable interrupts, and/or preemption,
307  * and the zpool_unmap_handle() must be called to undo those
308  * actions.  The code that uses the mapped handle should complete
309  * its operatons on the mapped handle memory quickly and unmap
310  * as soon as possible.  As the implementation may use per-cpu
311  * data, multiple handles should not be mapped concurrently on
312  * any cpu.
313  *
314  * Returns: A pointer to the handle's mapped memory area.
315  */
316 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
317                         enum zpool_mapmode mapmode)
318 {
319         return zpool->driver->map(zpool->pool, handle, mapmode);
320 }
321 
322 /**
323  * zpool_unmap_handle() - Unmap a previously mapped handle
324  * @pool        The zpool that the handle was allocated from
325  * @handle      The handle to unmap
326  *
327  * This unmaps a previously mapped handle.  Any locks or other
328  * actions that the implementation took in zpool_map_handle()
329  * will be undone here.  The memory area returned from
330  * zpool_map_handle() should no longer be used after this.
331  */
332 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
333 {
334         zpool->driver->unmap(zpool->pool, handle);
335 }
336 
337 /**
338  * zpool_get_total_size() - The total size of the pool
339  * @pool        The zpool to check
340  *
341  * This returns the total size in bytes of the pool.
342  *
343  * Returns: Total size of the zpool in bytes.
344  */
345 u64 zpool_get_total_size(struct zpool *zpool)
346 {
347         return zpool->driver->total_size(zpool->pool);
348 }
349 
350 static int __init init_zpool(void)
351 {
352         pr_info("loaded\n");
353         return 0;
354 }
355 
356 static void __exit exit_zpool(void)
357 {
358         pr_info("unloaded\n");
359 }
360 
361 module_init(init_zpool);
362 module_exit(exit_zpool);
363 
364 MODULE_LICENSE("GPL");
365 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
366 MODULE_DESCRIPTION("Common API for compressed memory storage");
367 

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