2 * zpool memory storage api
4 * Copyright (C) 2014 Dan Streetman
6 * This is a common frontend for memory storage pool implementations.
7 * Typically, this is used to store compressed memory.
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/list.h>
13 #include <linux/types.h>
15 #include <linux/slab.h>
16 #include <linux/spinlock.h>
17 #include <linux/module.h>
18 #include <linux/zpool.h>
23 struct zpool_driver *driver;
25 const struct zpool_ops *ops;
27 struct list_head list;
30 static LIST_HEAD(drivers_head);
31 static DEFINE_SPINLOCK(drivers_lock);
33 static LIST_HEAD(pools_head);
34 static DEFINE_SPINLOCK(pools_lock);
37 * zpool_register_driver() - register a zpool implementation.
38 * @driver: driver to register
40 void zpool_register_driver(struct zpool_driver *driver)
42 spin_lock(&drivers_lock);
43 atomic_set(&driver->refcount, 0);
44 list_add(&driver->list, &drivers_head);
45 spin_unlock(&drivers_lock);
47 EXPORT_SYMBOL(zpool_register_driver);
50 * zpool_unregister_driver() - unregister a zpool implementation.
51 * @driver: driver to unregister.
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.
59 int zpool_unregister_driver(struct zpool_driver *driver)
61 int ret = 0, refcount;
63 spin_lock(&drivers_lock);
64 refcount = atomic_read(&driver->refcount);
65 WARN_ON(refcount < 0);
69 list_del(&driver->list);
70 spin_unlock(&drivers_lock);
74 EXPORT_SYMBOL(zpool_unregister_driver);
76 static struct zpool_driver *zpool_get_driver(char *type)
78 struct zpool_driver *driver;
80 spin_lock(&drivers_lock);
81 list_for_each_entry(driver, &drivers_head, list) {
82 if (!strcmp(driver->type, type)) {
83 bool got = try_module_get(driver->owner);
86 atomic_inc(&driver->refcount);
87 spin_unlock(&drivers_lock);
88 return got ? driver : NULL;
92 spin_unlock(&drivers_lock);
96 static void zpool_put_driver(struct zpool_driver *driver)
98 atomic_dec(&driver->refcount);
99 module_put(driver->owner);
103 * zpool_has_pool() - Check if the pool driver is available
104 * @type The type of the zpool to check (e.g. zbud, zsmalloc)
106 * This checks if the @type pool driver is available. This will try to load
107 * the requested module, if needed, but there is no guarantee the module will
108 * still be loaded and available immediately after calling. If this returns
109 * true, the caller should assume the pool is available, but must be prepared
110 * to handle the @zpool_create_pool() returning failure. However if this
111 * returns false, the caller should assume the requested pool type is not
112 * available; either the requested pool type module does not exist, or could
113 * not be loaded, and calling @zpool_create_pool() with the pool type will
116 * Returns: true if @type pool is available, false if not
118 bool zpool_has_pool(char *type)
120 struct zpool_driver *driver = zpool_get_driver(type);
123 request_module("zpool-%s", type);
124 driver = zpool_get_driver(type);
130 zpool_put_driver(driver);
133 EXPORT_SYMBOL(zpool_has_pool);
136 * zpool_create_pool() - Create a new zpool
137 * @type The type of the zpool to create (e.g. zbud, zsmalloc)
138 * @name The name of the zpool (e.g. zram0, zswap)
139 * @gfp The GFP flags to use when allocating the pool.
140 * @ops The optional ops callback.
142 * This creates a new zpool of the specified type. The gfp flags will be
143 * used when allocating memory, if the implementation supports it. If the
144 * ops param is NULL, then the created zpool will not be shrinkable.
146 * Implementations must guarantee this to be thread-safe.
148 * Returns: New zpool on success, NULL on failure.
150 struct zpool *zpool_create_pool(char *type, char *name, gfp_t gfp,
151 const struct zpool_ops *ops)
153 struct zpool_driver *driver;
156 pr_debug("creating pool type %s\n", type);
158 driver = zpool_get_driver(type);
161 request_module("zpool-%s", type);
162 driver = zpool_get_driver(type);
166 pr_err("no driver for type %s\n", type);
170 zpool = kmalloc(sizeof(*zpool), gfp);
172 pr_err("couldn't create zpool - out of memory\n");
173 zpool_put_driver(driver);
177 zpool->type = driver->type;
178 zpool->driver = driver;
179 zpool->pool = driver->create(name, gfp, ops, zpool);
183 pr_err("couldn't create %s pool\n", type);
184 zpool_put_driver(driver);
189 pr_debug("created pool type %s\n", type);
191 spin_lock(&pools_lock);
192 list_add(&zpool->list, &pools_head);
193 spin_unlock(&pools_lock);
199 * zpool_destroy_pool() - Destroy a zpool
200 * @pool The zpool to destroy.
202 * Implementations must guarantee this to be thread-safe,
203 * however only when destroying different pools. The same
204 * pool should only be destroyed once, and should not be used
205 * after it is destroyed.
207 * This destroys an existing zpool. The zpool should not be in use.
209 void zpool_destroy_pool(struct zpool *zpool)
211 pr_debug("destroying pool type %s\n", zpool->type);
213 spin_lock(&pools_lock);
214 list_del(&zpool->list);
215 spin_unlock(&pools_lock);
216 zpool->driver->destroy(zpool->pool);
217 zpool_put_driver(zpool->driver);
222 * zpool_get_type() - Get the type of the zpool
223 * @pool The zpool to check
225 * This returns the type of the pool.
227 * Implementations must guarantee this to be thread-safe.
229 * Returns: The type of zpool.
231 char *zpool_get_type(struct zpool *zpool)
237 * zpool_malloc() - Allocate memory
238 * @pool The zpool to allocate from.
239 * @size The amount of memory to allocate.
240 * @gfp The GFP flags to use when allocating memory.
241 * @handle Pointer to the handle to set
243 * This allocates the requested amount of memory from the pool.
244 * The gfp flags will be used when allocating memory, if the
245 * implementation supports it. The provided @handle will be
246 * set to the allocated object handle.
248 * Implementations must guarantee this to be thread-safe.
250 * Returns: 0 on success, negative value on error.
252 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
253 unsigned long *handle)
255 return zpool->driver->malloc(zpool->pool, size, gfp, handle);
259 * zpool_free() - Free previously allocated memory
260 * @pool The zpool that allocated the memory.
261 * @handle The handle to the memory to free.
263 * This frees previously allocated memory. This does not guarantee
264 * that the pool will actually free memory, only that the memory
265 * in the pool will become available for use by the pool.
267 * Implementations must guarantee this to be thread-safe,
268 * however only when freeing different handles. The same
269 * handle should only be freed once, and should not be used
272 void zpool_free(struct zpool *zpool, unsigned long handle)
274 zpool->driver->free(zpool->pool, handle);
278 * zpool_shrink() - Shrink the pool size
279 * @pool The zpool to shrink.
280 * @pages The number of pages to shrink the pool.
281 * @reclaimed The number of pages successfully evicted.
283 * This attempts to shrink the actual memory size of the pool
284 * by evicting currently used handle(s). If the pool was
285 * created with no zpool_ops, or the evict call fails for any
286 * of the handles, this will fail. If non-NULL, the @reclaimed
287 * parameter will be set to the number of pages reclaimed,
288 * which may be more than the number of pages requested.
290 * Implementations must guarantee this to be thread-safe.
292 * Returns: 0 on success, negative value on error/failure.
294 int zpool_shrink(struct zpool *zpool, unsigned int pages,
295 unsigned int *reclaimed)
297 return zpool->driver->shrink(zpool->pool, pages, reclaimed);
301 * zpool_map_handle() - Map a previously allocated handle into memory
302 * @pool The zpool that the handle was allocated from
303 * @handle The handle to map
304 * @mm How the memory should be mapped
306 * This maps a previously allocated handle into memory. The @mm
307 * param indicates to the implementation how the memory will be
308 * used, i.e. read-only, write-only, read-write. If the
309 * implementation does not support it, the memory will be treated
312 * This may hold locks, disable interrupts, and/or preemption,
313 * and the zpool_unmap_handle() must be called to undo those
314 * actions. The code that uses the mapped handle should complete
315 * its operatons on the mapped handle memory quickly and unmap
316 * as soon as possible. As the implementation may use per-cpu
317 * data, multiple handles should not be mapped concurrently on
320 * Returns: A pointer to the handle's mapped memory area.
322 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
323 enum zpool_mapmode mapmode)
325 return zpool->driver->map(zpool->pool, handle, mapmode);
329 * zpool_unmap_handle() - Unmap a previously mapped handle
330 * @pool The zpool that the handle was allocated from
331 * @handle The handle to unmap
333 * This unmaps a previously mapped handle. Any locks or other
334 * actions that the implementation took in zpool_map_handle()
335 * will be undone here. The memory area returned from
336 * zpool_map_handle() should no longer be used after this.
338 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
340 zpool->driver->unmap(zpool->pool, handle);
344 * zpool_get_total_size() - The total size of the pool
345 * @pool The zpool to check
347 * This returns the total size in bytes of the pool.
349 * Returns: Total size of the zpool in bytes.
351 u64 zpool_get_total_size(struct zpool *zpool)
353 return zpool->driver->total_size(zpool->pool);
356 MODULE_LICENSE("GPL");
357 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
358 MODULE_DESCRIPTION("Common API for compressed memory storage");