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 static struct zpool_driver *zpool_get_driver(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_create_pool() - Create a new zpool
 104  * @type        The type of the zpool to create (e.g. zbud, zsmalloc)
 105  * @name        The name of the zpool (e.g. zram0, zswap)
 106  * @gfp         The GFP flags to use when allocating the pool.
 107  * @ops         The optional ops callback.
 108  *
 109  * This creates a new zpool of the specified type.  The gfp flags will be
 110  * used when allocating memory, if the implementation supports it.  If the
 111  * ops param is NULL, then the created zpool will not be shrinkable.
 112  *
 113  * Implementations must guarantee this to be thread-safe.
 114  *
 115  * Returns: New zpool on success, NULL on failure.
 116  */
 117 struct zpool *zpool_create_pool(char *type, char *name, gfp_t gfp,
 118                 struct zpool_ops *ops)
 119 {
 120         struct zpool_driver *driver;
 121         struct zpool *zpool;
 122
 123         pr_debug("creating pool type %s\n", type);
 124
 125         driver = zpool_get_driver(type);
 126
 127         if (!driver) {
 128                 request_module("zpool-%s", type);
 129                 driver = zpool_get_driver(type);
 130         }
 131
 132         if (!driver) {
 133                 pr_err("no driver for type %s\n", type);
 134                 return NULL;
 135         }
 136
 137         zpool = kmalloc(sizeof(*zpool), gfp);
 138         if (!zpool) {
 139                 pr_err("couldn't create zpool - out of memory\n");
 140                 zpool_put_driver(driver);
 141                 return NULL;
 142         }
 143
 144         zpool->type = driver->type;
 145         zpool->driver = driver;
 146         zpool->pool = driver->create(name, gfp, ops, zpool);
 147         zpool->ops = ops;
 148
 149         if (!zpool->pool) {
 150                 pr_err("couldn't create %s pool\n", type);
 151                 zpool_put_driver(driver);
 152                 kfree(zpool);
 153                 return NULL;
 154         }
 155
 156         pr_debug("created pool type %s\n", type);
 157
 158         spin_lock(&pools_lock);
 159         list_add(&zpool->list, &pools_head);
 160         spin_unlock(&pools_lock);
 161
 162         return zpool;
 163 }
 164
 165 /**
 166  * zpool_destroy_pool() - Destroy a zpool
 167  * @pool        The zpool to destroy.
 168  *
 169  * Implementations must guarantee this to be thread-safe,
 170  * however only when destroying different pools.  The same
 171  * pool should only be destroyed once, and should not be used
 172  * after it is destroyed.
 173  *
 174  * This destroys an existing zpool.  The zpool should not be in use.
 175  */
 176 void zpool_destroy_pool(struct zpool *zpool)
 177 {
 178         pr_debug("destroying pool type %s\n", zpool->type);
 179
 180         spin_lock(&pools_lock);
 181         list_del(&zpool->list);
 182         spin_unlock(&pools_lock);
 183         zpool->driver->destroy(zpool->pool);
 184         zpool_put_driver(zpool->driver);
 185         kfree(zpool);
 186 }
 187
 188 /**
 189  * zpool_get_type() - Get the type of the zpool
 190  * @pool        The zpool to check
 191  *
 192  * This returns the type of the pool.
 193  *
 194  * Implementations must guarantee this to be thread-safe.
 195  *
 196  * Returns: The type of zpool.
 197  */
 198 char *zpool_get_type(struct zpool *zpool)
 199 {
 200         return zpool->type;
 201 }
 202
 203 /**
 204  * zpool_malloc() - Allocate memory
 205  * @pool        The zpool to allocate from.
 206  * @size        The amount of memory to allocate.
 207  * @gfp         The GFP flags to use when allocating memory.
 208  * @handle      Pointer to the handle to set
 209  *
 210  * This allocates the requested amount of memory from the pool.
 211  * The gfp flags will be used when allocating memory, if the
 212  * implementation supports it.  The provided @handle will be
 213  * set to the allocated object handle.
 214  *
 215  * Implementations must guarantee this to be thread-safe.
 216  *
 217  * Returns: 0 on success, negative value on error.
 218  */
 219 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
 220                         unsigned long *handle)
 221 {
 222         return zpool->driver->malloc(zpool->pool, size, gfp, handle);
 223 }
 224
 225 /**
 226  * zpool_free() - Free previously allocated memory
 227  * @pool        The zpool that allocated the memory.
 228  * @handle      The handle to the memory to free.
 229  *
 230  * This frees previously allocated memory.  This does not guarantee
 231  * that the pool will actually free memory, only that the memory
 232  * in the pool will become available for use by the pool.
 233  *
 234  * Implementations must guarantee this to be thread-safe,
 235  * however only when freeing different handles.  The same
 236  * handle should only be freed once, and should not be used
 237  * after freeing.
 238  */
 239 void zpool_free(struct zpool *zpool, unsigned long handle)
 240 {
 241         zpool->driver->free(zpool->pool, handle);
 242 }
 243
 244 /**
 245  * zpool_shrink() - Shrink the pool size
 246  * @pool        The zpool to shrink.
 247  * @pages       The number of pages to shrink the pool.
 248  * @reclaimed   The number of pages successfully evicted.
 249  *
 250  * This attempts to shrink the actual memory size of the pool
 251  * by evicting currently used handle(s).  If the pool was
 252  * created with no zpool_ops, or the evict call fails for any
 253  * of the handles, this will fail.  If non-NULL, the @reclaimed
 254  * parameter will be set to the number of pages reclaimed,
 255  * which may be more than the number of pages requested.
 256  *
 257  * Implementations must guarantee this to be thread-safe.
 258  *
 259  * Returns: 0 on success, negative value on error/failure.
 260  */
 261 int zpool_shrink(struct zpool *zpool, unsigned int pages,
 262                         unsigned int *reclaimed)
 263 {
 264         return zpool->driver->shrink(zpool->pool, pages, reclaimed);
 265 }
 266
 267 /**
 268  * zpool_map_handle() - Map a previously allocated handle into memory
 269  * @pool        The zpool that the handle was allocated from
 270  * @handle      The handle to map
 271  * @mm          How the memory should be mapped
 272  *
 273  * This maps a previously allocated handle into memory.  The @mm
 274  * param indicates to the implementation how the memory will be
 275  * used, i.e. read-only, write-only, read-write.  If the
 276  * implementation does not support it, the memory will be treated
 277  * as read-write.
 278  *
 279  * This may hold locks, disable interrupts, and/or preemption,
 280  * and the zpool_unmap_handle() must be called to undo those
 281  * actions.  The code that uses the mapped handle should complete
 282  * its operatons on the mapped handle memory quickly and unmap
 283  * as soon as possible.  As the implementation may use per-cpu
 284  * data, multiple handles should not be mapped concurrently on
 285  * any cpu.
 286  *
 287  * Returns: A pointer to the handle's mapped memory area.
 288  */
 289 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
 290                         enum zpool_mapmode mapmode)
 291 {
 292         return zpool->driver->map(zpool->pool, handle, mapmode);
 293 }
 294
 295 /**
 296  * zpool_unmap_handle() - Unmap a previously mapped handle
 297  * @pool        The zpool that the handle was allocated from
 298  * @handle      The handle to unmap
 299  *
 300  * This unmaps a previously mapped handle.  Any locks or other
 301  * actions that the implementation took in zpool_map_handle()
 302  * will be undone here.  The memory area returned from
 303  * zpool_map_handle() should no longer be used after this.
 304  */
 305 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
 306 {
 307         zpool->driver->unmap(zpool->pool, handle);
 308 }
 309
 310 /**
 311  * zpool_get_total_size() - The total size of the pool
 312  * @pool        The zpool to check
 313  *
 314  * This returns the total size in bytes of the pool.
 315  *
 316  * Returns: Total size of the zpool in bytes.
 317  */
 318 u64 zpool_get_total_size(struct zpool *zpool)
 319 {
 320         return zpool->driver->total_size(zpool->pool);
 321 }
 322
 323 static int __init init_zpool(void)
 324 {
 325         pr_info("loaded\n");
 326         return 0;
 327 }
 328
 329 static void __exit exit_zpool(void)
 330 {
 331         pr_info("unloaded\n");
 332 }
 333
 334 module_init(init_zpool);
 335 module_exit(exit_zpool);
 336
 337 MODULE_LICENSE("GPL");
 338 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
 339 MODULE_DESCRIPTION("Common API for compressed memory storage");