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 bool evictable; 25 26 struct list_head list; 27 }; 28 29 static LIST_HEAD(drivers_head); 30 static DEFINE_SPINLOCK(drivers_lock); 31 32 static LIST_HEAD(pools_head); 33 static DEFINE_SPINLOCK(pools_lock); 34 35 /** 36 * zpool_register_driver() - register a zpool implementation. 37 * @driver: driver to register 38 */ 39 void zpool_register_driver(struct zpool_driver *driver) 40 { 41 spin_lock(&drivers_lock); 42 atomic_set(&driver->refcount, 0); 43 list_add(&driver->list, &drivers_head); 44 spin_unlock(&drivers_lock); 45 } 46 EXPORT_SYMBOL(zpool_register_driver); 47 48 /** 49 * zpool_unregister_driver() - unregister a zpool implementation. 50 * @driver: driver to unregister. 51 * 52 * Module usage counting is used to prevent using a driver 53 * while/after unloading, so if this is called from module 54 * exit function, this should never fail; if called from 55 * other than the module exit function, and this returns 56 * failure, the driver is in use and must remain available. 57 */ 58 int zpool_unregister_driver(struct zpool_driver *driver) 59 { 60 int ret = 0, refcount; 61 62 spin_lock(&drivers_lock); 63 refcount = atomic_read(&driver->refcount); 64 WARN_ON(refcount < 0); 65 if (refcount > 0) 66 ret = -EBUSY; 67 else 68 list_del(&driver->list); 69 spin_unlock(&drivers_lock); 70 71 return ret; 72 } 73 EXPORT_SYMBOL(zpool_unregister_driver); 74 75 /* this assumes @type is null-terminated. */ 76 static struct zpool_driver *zpool_get_driver(const char *type) 77 { 78 struct zpool_driver *driver; 79 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); 84 85 if (got) 86 atomic_inc(&driver->refcount); 87 spin_unlock(&drivers_lock); 88 return got ? driver : NULL; 89 } 90 } 91 92 spin_unlock(&drivers_lock); 93 return NULL; 94 } 95 96 static void zpool_put_driver(struct zpool_driver *driver) 97 { 98 atomic_dec(&driver->refcount); 99 module_put(driver->owner); 100 } 101 102 /** 103 * zpool_has_pool() - Check if the pool driver is available 104 * @type: The type of the zpool to check (e.g. zbud, zsmalloc) 105 * 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 114 * fail. 115 * 116 * The @type string must be null-terminated. 117 * 118 * Returns: true if @type pool is available, false if not 119 */ 120 bool zpool_has_pool(char *type) 121 { 122 struct zpool_driver *driver = zpool_get_driver(type); 123 124 if (!driver) { 125 request_module("zpool-%s", type); 126 driver = zpool_get_driver(type); 127 } 128 129 if (!driver) 130 return false; 131 132 zpool_put_driver(driver); 133 return true; 134 } 135 EXPORT_SYMBOL(zpool_has_pool); 136 137 /** 138 * zpool_create_pool() - Create a new zpool 139 * @type: The type of the zpool to create (e.g. zbud, zsmalloc) 140 * @name: The name of the zpool (e.g. zram0, zswap) 141 * @gfp: The GFP flags to use when allocating the pool. 142 * @ops: The optional ops callback. 143 * 144 * This creates a new zpool of the specified type. The gfp flags will be 145 * used when allocating memory, if the implementation supports it. If the 146 * ops param is NULL, then the created zpool will not be evictable. 147 * 148 * Implementations must guarantee this to be thread-safe. 149 * 150 * The @type and @name strings must be null-terminated. 151 * 152 * Returns: New zpool on success, NULL on failure. 153 */ 154 struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp, 155 const struct zpool_ops *ops) 156 { 157 struct zpool_driver *driver; 158 struct zpool *zpool; 159 160 pr_debug("creating pool type %s\n", type); 161 162 driver = zpool_get_driver(type); 163 164 if (!driver) { 165 request_module("zpool-%s", type); 166 driver = zpool_get_driver(type); 167 } 168 169 if (!driver) { 170 pr_err("no driver for type %s\n", type); 171 return NULL; 172 } 173 174 zpool = kmalloc(sizeof(*zpool), gfp); 175 if (!zpool) { 176 pr_err("couldn't create zpool - out of memory\n"); 177 zpool_put_driver(driver); 178 return NULL; 179 } 180 181 zpool->driver = driver; 182 zpool->pool = driver->create(name, gfp, ops, zpool); 183 zpool->ops = ops; 184 zpool->evictable = driver->shrink && ops && ops->evict; 185 186 if (!zpool->pool) { 187 pr_err("couldn't create %s pool\n", type); 188 zpool_put_driver(driver); 189 kfree(zpool); 190 return NULL; 191 } 192 193 pr_debug("created pool type %s\n", type); 194 195 spin_lock(&pools_lock); 196 list_add(&zpool->list, &pools_head); 197 spin_unlock(&pools_lock); 198 199 return zpool; 200 } 201 202 /** 203 * zpool_destroy_pool() - Destroy a zpool 204 * @zpool: The zpool to destroy. 205 * 206 * Implementations must guarantee this to be thread-safe, 207 * however only when destroying different pools. The same 208 * pool should only be destroyed once, and should not be used 209 * after it is destroyed. 210 * 211 * This destroys an existing zpool. The zpool should not be in use. 212 */ 213 void zpool_destroy_pool(struct zpool *zpool) 214 { 215 pr_debug("destroying pool type %s\n", zpool->driver->type); 216 217 spin_lock(&pools_lock); 218 list_del(&zpool->list); 219 spin_unlock(&pools_lock); 220 zpool->driver->destroy(zpool->pool); 221 zpool_put_driver(zpool->driver); 222 kfree(zpool); 223 } 224 225 /** 226 * zpool_get_type() - Get the type of the zpool 227 * @zpool: The zpool to check 228 * 229 * This returns the type of the pool. 230 * 231 * Implementations must guarantee this to be thread-safe. 232 * 233 * Returns: The type of zpool. 234 */ 235 const char *zpool_get_type(struct zpool *zpool) 236 { 237 return zpool->driver->type; 238 } 239 240 /** 241 * zpool_malloc() - Allocate memory 242 * @zpool: The zpool to allocate from. 243 * @size: The amount of memory to allocate. 244 * @gfp: The GFP flags to use when allocating memory. 245 * @handle: Pointer to the handle to set 246 * 247 * This allocates the requested amount of memory from the pool. 248 * The gfp flags will be used when allocating memory, if the 249 * implementation supports it. The provided @handle will be 250 * set to the allocated object handle. 251 * 252 * Implementations must guarantee this to be thread-safe. 253 * 254 * Returns: 0 on success, negative value on error. 255 */ 256 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp, 257 unsigned long *handle) 258 { 259 return zpool->driver->malloc(zpool->pool, size, gfp, handle); 260 } 261 262 /** 263 * zpool_free() - Free previously allocated memory 264 * @zpool: The zpool that allocated the memory. 265 * @handle: The handle to the memory to free. 266 * 267 * This frees previously allocated memory. This does not guarantee 268 * that the pool will actually free memory, only that the memory 269 * in the pool will become available for use by the pool. 270 * 271 * Implementations must guarantee this to be thread-safe, 272 * however only when freeing different handles. The same 273 * handle should only be freed once, and should not be used 274 * after freeing. 275 */ 276 void zpool_free(struct zpool *zpool, unsigned long handle) 277 { 278 zpool->driver->free(zpool->pool, handle); 279 } 280 281 /** 282 * zpool_shrink() - Shrink the pool size 283 * @zpool: The zpool to shrink. 284 * @pages: The number of pages to shrink the pool. 285 * @reclaimed: The number of pages successfully evicted. 286 * 287 * This attempts to shrink the actual memory size of the pool 288 * by evicting currently used handle(s). If the pool was 289 * created with no zpool_ops, or the evict call fails for any 290 * of the handles, this will fail. If non-NULL, the @reclaimed 291 * parameter will be set to the number of pages reclaimed, 292 * which may be more than the number of pages requested. 293 * 294 * Implementations must guarantee this to be thread-safe. 295 * 296 * Returns: 0 on success, negative value on error/failure. 297 */ 298 int zpool_shrink(struct zpool *zpool, unsigned int pages, 299 unsigned int *reclaimed) 300 { 301 return zpool->driver->shrink ? 302 zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL; 303 } 304 305 /** 306 * zpool_map_handle() - Map a previously allocated handle into memory 307 * @zpool: The zpool that the handle was allocated from 308 * @handle: The handle to map 309 * @mapmode: How the memory should be mapped 310 * 311 * This maps a previously allocated handle into memory. The @mapmode 312 * param indicates to the implementation how the memory will be 313 * used, i.e. read-only, write-only, read-write. If the 314 * implementation does not support it, the memory will be treated 315 * as read-write. 316 * 317 * This may hold locks, disable interrupts, and/or preemption, 318 * and the zpool_unmap_handle() must be called to undo those 319 * actions. The code that uses the mapped handle should complete 320 * its operatons on the mapped handle memory quickly and unmap 321 * as soon as possible. As the implementation may use per-cpu 322 * data, multiple handles should not be mapped concurrently on 323 * any cpu. 324 * 325 * Returns: A pointer to the handle's mapped memory area. 326 */ 327 void *zpool_map_handle(struct zpool *zpool, unsigned long handle, 328 enum zpool_mapmode mapmode) 329 { 330 return zpool->driver->map(zpool->pool, handle, mapmode); 331 } 332 333 /** 334 * zpool_unmap_handle() - Unmap a previously mapped handle 335 * @zpool: The zpool that the handle was allocated from 336 * @handle: The handle to unmap 337 * 338 * This unmaps a previously mapped handle. Any locks or other 339 * actions that the implementation took in zpool_map_handle() 340 * will be undone here. The memory area returned from 341 * zpool_map_handle() should no longer be used after this. 342 */ 343 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle) 344 { 345 zpool->driver->unmap(zpool->pool, handle); 346 } 347 348 /** 349 * zpool_get_total_size() - The total size of the pool 350 * @zpool: The zpool to check 351 * 352 * This returns the total size in bytes of the pool. 353 * 354 * Returns: Total size of the zpool in bytes. 355 */ 356 u64 zpool_get_total_size(struct zpool *zpool) 357 { 358 return zpool->driver->total_size(zpool->pool); 359 } 360 361 /** 362 * zpool_evictable() - Test if zpool is potentially evictable 363 * @zpool: The zpool to test 364 * 365 * Zpool is only potentially evictable when it's created with struct 366 * zpool_ops.evict and its driver implements struct zpool_driver.shrink. 367 * 368 * However, it doesn't necessarily mean driver will use zpool_ops.evict 369 * in its implementation of zpool_driver.shrink. It could do internal 370 * defragmentation instead. 371 * 372 * Returns: true if potentially evictable; false otherwise. 373 */ 374 bool zpool_evictable(struct zpool *zpool) 375 { 376 return zpool->evictable; 377 } 378 379 MODULE_LICENSE("GPL"); 380 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>"); 381 MODULE_DESCRIPTION("Common API for compressed memory storage"); 382