mm/zpool.c

   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");