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         const 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_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  * Returns: true if @type pool is available, false if not
 117  */
 118 bool zpool_has_pool(char *type)
 119 {
 120         struct zpool_driver *driver = zpool_get_driver(type);
 121
 122         if (!driver) {
 123                 request_module("zpool-%s", type);
 124                 driver = zpool_get_driver(type);
 125         }
 126
 127         if (!driver)
 128                 return false;
 129
 130         zpool_put_driver(driver);
 131         return true;
 132 }
 133 EXPORT_SYMBOL(zpool_has_pool);
 134
 135 /**
 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.
 141  *
 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.
 145  *
 146  * Implementations must guarantee this to be thread-safe.
 147  *
 148  * Returns: New zpool on success, NULL on failure.
 149  */
 150 struct zpool *zpool_create_pool(char *type, char *name, gfp_t gfp,
 151                 const struct zpool_ops *ops)
 152 {
 153         struct zpool_driver *driver;
 154         struct zpool *zpool;
 155
 156         pr_debug("creating pool type %s\n", type);
 157
 158         driver = zpool_get_driver(type);
 159
 160         if (!driver) {
 161                 request_module("zpool-%s", type);
 162                 driver = zpool_get_driver(type);
 163         }
 164
 165         if (!driver) {
 166                 pr_err("no driver for type %s\n", type);
 167                 return NULL;
 168         }
 169
 170         zpool = kmalloc(sizeof(*zpool), gfp);
 171         if (!zpool) {
 172                 pr_err("couldn't create zpool - out of memory\n");
 173                 zpool_put_driver(driver);
 174                 return NULL;
 175         }
 176
 177         zpool->type = driver->type;
 178         zpool->driver = driver;
 179         zpool->pool = driver->create(name, gfp, ops, zpool);
 180         zpool->ops = ops;
 181
 182         if (!zpool->pool) {
 183                 pr_err("couldn't create %s pool\n", type);
 184                 zpool_put_driver(driver);
 185                 kfree(zpool);
 186                 return NULL;
 187         }
 188
 189         pr_debug("created pool type %s\n", type);
 190
 191         spin_lock(&pools_lock);
 192         list_add(&zpool->list, &pools_head);
 193         spin_unlock(&pools_lock);
 194
 195         return zpool;
 196 }
 197
 198 /**
 199  * zpool_destroy_pool() - Destroy a zpool
 200  * @pool        The zpool to destroy.
 201  *
 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.
 206  *
 207  * This destroys an existing zpool.  The zpool should not be in use.
 208  */
 209 void zpool_destroy_pool(struct zpool *zpool)
 210 {
 211         pr_debug("destroying pool type %s\n", zpool->type);
 212
 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);
 218         kfree(zpool);
 219 }
 220
 221 /**
 222  * zpool_get_type() - Get the type of the zpool
 223  * @pool        The zpool to check
 224  *
 225  * This returns the type of the pool.
 226  *
 227  * Implementations must guarantee this to be thread-safe.
 228  *
 229  * Returns: The type of zpool.
 230  */
 231 char *zpool_get_type(struct zpool *zpool)
 232 {
 233         return zpool->type;
 234 }
 235
 236 /**
 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
 242  *
 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.
 247  *
 248  * Implementations must guarantee this to be thread-safe.
 249  *
 250  * Returns: 0 on success, negative value on error.
 251  */
 252 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
 253                         unsigned long *handle)
 254 {
 255         return zpool->driver->malloc(zpool->pool, size, gfp, handle);
 256 }
 257
 258 /**
 259  * zpool_free() - Free previously allocated memory
 260  * @pool        The zpool that allocated the memory.
 261  * @handle      The handle to the memory to free.
 262  *
 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.
 266  *
 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
 270  * after freeing.
 271  */
 272 void zpool_free(struct zpool *zpool, unsigned long handle)
 273 {
 274         zpool->driver->free(zpool->pool, handle);
 275 }
 276
 277 /**
 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.
 282  *
 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.
 289  *
 290  * Implementations must guarantee this to be thread-safe.
 291  *
 292  * Returns: 0 on success, negative value on error/failure.
 293  */
 294 int zpool_shrink(struct zpool *zpool, unsigned int pages,
 295                         unsigned int *reclaimed)
 296 {
 297         return zpool->driver->shrink(zpool->pool, pages, reclaimed);
 298 }
 299
 300 /**
 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
 305  *
 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
 310  * as read-write.
 311  *
 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
 318  * any cpu.
 319  *
 320  * Returns: A pointer to the handle's mapped memory area.
 321  */
 322 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
 323                         enum zpool_mapmode mapmode)
 324 {
 325         return zpool->driver->map(zpool->pool, handle, mapmode);
 326 }
 327
 328 /**
 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
 332  *
 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.
 337  */
 338 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
 339 {
 340         zpool->driver->unmap(zpool->pool, handle);
 341 }
 342
 343 /**
 344  * zpool_get_total_size() - The total size of the pool
 345  * @pool        The zpool to check
 346  *
 347  * This returns the total size in bytes of the pool.
 348  *
 349  * Returns: Total size of the zpool in bytes.
 350  */
 351 u64 zpool_get_total_size(struct zpool *zpool)
 352 {
 353         return zpool->driver->total_size(zpool->pool);
 354 }
 355
 356 MODULE_LICENSE("GPL");
 357 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
 358 MODULE_DESCRIPTION("Common API for compressed memory storage");