mm/zpool.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * zpool memory storage api
   4  *
   5  * Copyright (C) 2014 Dan Streetman
   6  *
   7  * This is a common frontend for memory storage pool implementations.
   8  * Typically, this is used to store compressed memory.
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/list.h>
  14 #include <linux/types.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/spinlock.h>
  18 #include <linux/module.h>
  19 #include <linux/zpool.h>
  20
  21 struct zpool {
  22         struct zpool_driver *driver;
  23         void *pool;
  24         const struct zpool_ops *ops;
  25         bool evictable;
  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 /* this assumes @type is null-terminated. */
  77 static struct zpool_driver *zpool_get_driver(const char *type)
  78 {
  79         struct zpool_driver *driver;
  80
  81         spin_lock(&drivers_lock);
  82         list_for_each_entry(driver, &drivers_head, list) {
  83                 if (!strcmp(driver->type, type)) {
  84                         bool got = try_module_get(driver->owner);
  85
  86                         if (got)
  87                                 atomic_inc(&driver->refcount);
  88                         spin_unlock(&drivers_lock);
  89                         return got ? driver : NULL;
  90                 }
  91         }
  92
  93         spin_unlock(&drivers_lock);
  94         return NULL;
  95 }
  96
  97 static void zpool_put_driver(struct zpool_driver *driver)
  98 {
  99         atomic_dec(&driver->refcount);
 100         module_put(driver->owner);
 101 }
 102
 103 /**
 104  * zpool_has_pool() - Check if the pool driver is available
 105  * @type:       The type of the zpool to check (e.g. zbud, zsmalloc)
 106  *
 107  * This checks if the @type pool driver is available.  This will try to load
 108  * the requested module, if needed, but there is no guarantee the module will
 109  * still be loaded and available immediately after calling.  If this returns
 110  * true, the caller should assume the pool is available, but must be prepared
 111  * to handle the @zpool_create_pool() returning failure.  However if this
 112  * returns false, the caller should assume the requested pool type is not
 113  * available; either the requested pool type module does not exist, or could
 114  * not be loaded, and calling @zpool_create_pool() with the pool type will
 115  * fail.
 116  *
 117  * The @type string must be null-terminated.
 118  *
 119  * Returns: true if @type pool is available, false if not
 120  */
 121 bool zpool_has_pool(char *type)
 122 {
 123         struct zpool_driver *driver = zpool_get_driver(type);
 124
 125         if (!driver) {
 126                 request_module("zpool-%s", type);
 127                 driver = zpool_get_driver(type);
 128         }
 129
 130         if (!driver)
 131                 return false;
 132
 133         zpool_put_driver(driver);
 134         return true;
 135 }
 136 EXPORT_SYMBOL(zpool_has_pool);
 137
 138 /**
 139  * zpool_create_pool() - Create a new zpool
 140  * @type:       The type of the zpool to create (e.g. zbud, zsmalloc)
 141  * @name:       The name of the zpool (e.g. zram0, zswap)
 142  * @gfp:        The GFP flags to use when allocating the pool.
 143  * @ops:        The optional ops callback.
 144  *
 145  * This creates a new zpool of the specified type.  The gfp flags will be
 146  * used when allocating memory, if the implementation supports it.  If the
 147  * ops param is NULL, then the created zpool will not be evictable.
 148  *
 149  * Implementations must guarantee this to be thread-safe.
 150  *
 151  * The @type and @name strings must be null-terminated.
 152  *
 153  * Returns: New zpool on success, NULL on failure.
 154  */
 155 struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
 156                 const struct zpool_ops *ops)
 157 {
 158         struct zpool_driver *driver;
 159         struct zpool *zpool;
 160
 161         pr_debug("creating pool type %s\n", type);
 162
 163         driver = zpool_get_driver(type);
 164
 165         if (!driver) {
 166                 request_module("zpool-%s", type);
 167                 driver = zpool_get_driver(type);
 168         }
 169
 170         if (!driver) {
 171                 pr_err("no driver for type %s\n", type);
 172                 return NULL;
 173         }
 174
 175         zpool = kmalloc(sizeof(*zpool), gfp);
 176         if (!zpool) {
 177                 pr_err("couldn't create zpool - out of memory\n");
 178                 zpool_put_driver(driver);
 179                 return NULL;
 180         }
 181
 182         zpool->driver = driver;
 183         zpool->pool = driver->create(name, gfp, ops, zpool);
 184         zpool->ops = ops;
 185         zpool->evictable = driver->shrink && ops && ops->evict;
 186
 187         if (!zpool->pool) {
 188                 pr_err("couldn't create %s pool\n", type);
 189                 zpool_put_driver(driver);
 190                 kfree(zpool);
 191                 return NULL;
 192         }
 193
 194         pr_debug("created pool type %s\n", type);
 195
 196         spin_lock(&pools_lock);
 197         list_add(&zpool->list, &pools_head);
 198         spin_unlock(&pools_lock);
 199
 200         return zpool;
 201 }
 202
 203 /**
 204  * zpool_destroy_pool() - Destroy a zpool
 205  * @zpool:      The zpool to destroy.
 206  *
 207  * Implementations must guarantee this to be thread-safe,
 208  * however only when destroying different pools.  The same
 209  * pool should only be destroyed once, and should not be used
 210  * after it is destroyed.
 211  *
 212  * This destroys an existing zpool.  The zpool should not be in use.
 213  */
 214 void zpool_destroy_pool(struct zpool *zpool)
 215 {
 216         pr_debug("destroying pool type %s\n", zpool->driver->type);
 217
 218         spin_lock(&pools_lock);
 219         list_del(&zpool->list);
 220         spin_unlock(&pools_lock);
 221         zpool->driver->destroy(zpool->pool);
 222         zpool_put_driver(zpool->driver);
 223         kfree(zpool);
 224 }
 225
 226 /**
 227  * zpool_get_type() - Get the type of the zpool
 228  * @zpool:      The zpool to check
 229  *
 230  * This returns the type of the pool.
 231  *
 232  * Implementations must guarantee this to be thread-safe.
 233  *
 234  * Returns: The type of zpool.
 235  */
 236 const char *zpool_get_type(struct zpool *zpool)
 237 {
 238         return zpool->driver->type;
 239 }
 240
 241 /**
 242  * zpool_malloc() - Allocate memory
 243  * @zpool:      The zpool to allocate from.
 244  * @size:       The amount of memory to allocate.
 245  * @gfp:        The GFP flags to use when allocating memory.
 246  * @handle:     Pointer to the handle to set
 247  *
 248  * This allocates the requested amount of memory from the pool.
 249  * The gfp flags will be used when allocating memory, if the
 250  * implementation supports it.  The provided @handle will be
 251  * set to the allocated object handle.
 252  *
 253  * Implementations must guarantee this to be thread-safe.
 254  *
 255  * Returns: 0 on success, negative value on error.
 256  */
 257 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
 258                         unsigned long *handle)
 259 {
 260         return zpool->driver->malloc(zpool->pool, size, gfp, handle);
 261 }
 262
 263 /**
 264  * zpool_free() - Free previously allocated memory
 265  * @zpool:      The zpool that allocated the memory.
 266  * @handle:     The handle to the memory to free.
 267  *
 268  * This frees previously allocated memory.  This does not guarantee
 269  * that the pool will actually free memory, only that the memory
 270  * in the pool will become available for use by the pool.
 271  *
 272  * Implementations must guarantee this to be thread-safe,
 273  * however only when freeing different handles.  The same
 274  * handle should only be freed once, and should not be used
 275  * after freeing.
 276  */
 277 void zpool_free(struct zpool *zpool, unsigned long handle)
 278 {
 279         zpool->driver->free(zpool->pool, handle);
 280 }
 281
 282 /**
 283  * zpool_shrink() - Shrink the pool size
 284  * @zpool:      The zpool to shrink.
 285  * @pages:      The number of pages to shrink the pool.
 286  * @reclaimed:  The number of pages successfully evicted.
 287  *
 288  * This attempts to shrink the actual memory size of the pool
 289  * by evicting currently used handle(s).  If the pool was
 290  * created with no zpool_ops, or the evict call fails for any
 291  * of the handles, this will fail.  If non-NULL, the @reclaimed
 292  * parameter will be set to the number of pages reclaimed,
 293  * which may be more than the number of pages requested.
 294  *
 295  * Implementations must guarantee this to be thread-safe.
 296  *
 297  * Returns: 0 on success, negative value on error/failure.
 298  */
 299 int zpool_shrink(struct zpool *zpool, unsigned int pages,
 300                         unsigned int *reclaimed)
 301 {
 302         return zpool->driver->shrink ?
 303                zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
 304 }
 305
 306 /**
 307  * zpool_map_handle() - Map a previously allocated handle into memory
 308  * @zpool:      The zpool that the handle was allocated from
 309  * @handle:     The handle to map
 310  * @mapmode:    How the memory should be mapped
 311  *
 312  * This maps a previously allocated handle into memory.  The @mapmode
 313  * param indicates to the implementation how the memory will be
 314  * used, i.e. read-only, write-only, read-write.  If the
 315  * implementation does not support it, the memory will be treated
 316  * as read-write.
 317  *
 318  * This may hold locks, disable interrupts, and/or preemption,
 319  * and the zpool_unmap_handle() must be called to undo those
 320  * actions.  The code that uses the mapped handle should complete
 321  * its operatons on the mapped handle memory quickly and unmap
 322  * as soon as possible.  As the implementation may use per-cpu
 323  * data, multiple handles should not be mapped concurrently on
 324  * any cpu.
 325  *
 326  * Returns: A pointer to the handle's mapped memory area.
 327  */
 328 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
 329                         enum zpool_mapmode mapmode)
 330 {
 331         return zpool->driver->map(zpool->pool, handle, mapmode);
 332 }
 333
 334 /**
 335  * zpool_unmap_handle() - Unmap a previously mapped handle
 336  * @zpool:      The zpool that the handle was allocated from
 337  * @handle:     The handle to unmap
 338  *
 339  * This unmaps a previously mapped handle.  Any locks or other
 340  * actions that the implementation took in zpool_map_handle()
 341  * will be undone here.  The memory area returned from
 342  * zpool_map_handle() should no longer be used after this.
 343  */
 344 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
 345 {
 346         zpool->driver->unmap(zpool->pool, handle);
 347 }
 348
 349 /**
 350  * zpool_get_total_size() - The total size of the pool
 351  * @zpool:      The zpool to check
 352  *
 353  * This returns the total size in bytes of the pool.
 354  *
 355  * Returns: Total size of the zpool in bytes.
 356  */
 357 u64 zpool_get_total_size(struct zpool *zpool)
 358 {
 359         return zpool->driver->total_size(zpool->pool);
 360 }
 361
 362 /**
 363  * zpool_evictable() - Test if zpool is potentially evictable
 364  * @zpool:      The zpool to test
 365  *
 366  * Zpool is only potentially evictable when it's created with struct
 367  * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
 368  *
 369  * However, it doesn't necessarily mean driver will use zpool_ops.evict
 370  * in its implementation of zpool_driver.shrink. It could do internal
 371  * defragmentation instead.
 372  *
 373  * Returns: true if potentially evictable; false otherwise.
 374  */
 375 bool zpool_evictable(struct zpool *zpool)
 376 {
 377         return zpool->evictable;
 378 }
 379
 380 MODULE_LICENSE("GPL");
 381 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
 382 MODULE_DESCRIPTION("Common API for compressed memory storage");