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 };
  25
  26 static LIST_HEAD(drivers_head);
  27 static DEFINE_SPINLOCK(drivers_lock);
  28
  29 /**
  30  * zpool_register_driver() - register a zpool implementation.
  31  * @driver:     driver to register
  32  */
  33 void zpool_register_driver(struct zpool_driver *driver)
  34 {
  35         spin_lock(&drivers_lock);
  36         atomic_set(&driver->refcount, 0);
  37         list_add(&driver->list, &drivers_head);
  38         spin_unlock(&drivers_lock);
  39 }
  40 EXPORT_SYMBOL(zpool_register_driver);
  41
  42 /**
  43  * zpool_unregister_driver() - unregister a zpool implementation.
  44  * @driver:     driver to unregister.
  45  *
  46  * Module usage counting is used to prevent using a driver
  47  * while/after unloading, so if this is called from module
  48  * exit function, this should never fail; if called from
  49  * other than the module exit function, and this returns
  50  * failure, the driver is in use and must remain available.
  51  */
  52 int zpool_unregister_driver(struct zpool_driver *driver)
  53 {
  54         int ret = 0, refcount;
  55
  56         spin_lock(&drivers_lock);
  57         refcount = atomic_read(&driver->refcount);
  58         WARN_ON(refcount < 0);
  59         if (refcount > 0)
  60                 ret = -EBUSY;
  61         else
  62                 list_del(&driver->list);
  63         spin_unlock(&drivers_lock);
  64
  65         return ret;
  66 }
  67 EXPORT_SYMBOL(zpool_unregister_driver);
  68
  69 /* this assumes @type is null-terminated. */
  70 static struct zpool_driver *zpool_get_driver(const char *type)
  71 {
  72         struct zpool_driver *driver;
  73
  74         spin_lock(&drivers_lock);
  75         list_for_each_entry(driver, &drivers_head, list) {
  76                 if (!strcmp(driver->type, type)) {
  77                         bool got = try_module_get(driver->owner);
  78
  79                         if (got)
  80                                 atomic_inc(&driver->refcount);
  81                         spin_unlock(&drivers_lock);
  82                         return got ? driver : NULL;
  83                 }
  84         }
  85
  86         spin_unlock(&drivers_lock);
  87         return NULL;
  88 }
  89
  90 static void zpool_put_driver(struct zpool_driver *driver)
  91 {
  92         atomic_dec(&driver->refcount);
  93         module_put(driver->owner);
  94 }
  95
  96 /**
  97  * zpool_has_pool() - Check if the pool driver is available
  98  * @type:       The type of the zpool to check (e.g. zbud, zsmalloc)
  99  *
 100  * This checks if the @type pool driver is available.  This will try to load
 101  * the requested module, if needed, but there is no guarantee the module will
 102  * still be loaded and available immediately after calling.  If this returns
 103  * true, the caller should assume the pool is available, but must be prepared
 104  * to handle the @zpool_create_pool() returning failure.  However if this
 105  * returns false, the caller should assume the requested pool type is not
 106  * available; either the requested pool type module does not exist, or could
 107  * not be loaded, and calling @zpool_create_pool() with the pool type will
 108  * fail.
 109  *
 110  * The @type string must be null-terminated.
 111  *
 112  * Returns: true if @type pool is available, false if not
 113  */
 114 bool zpool_has_pool(char *type)
 115 {
 116         struct zpool_driver *driver = zpool_get_driver(type);
 117
 118         if (!driver) {
 119                 request_module("zpool-%s", type);
 120                 driver = zpool_get_driver(type);
 121         }
 122
 123         if (!driver)
 124                 return false;
 125
 126         zpool_put_driver(driver);
 127         return true;
 128 }
 129 EXPORT_SYMBOL(zpool_has_pool);
 130
 131 /**
 132  * zpool_create_pool() - Create a new zpool
 133  * @type:       The type of the zpool to create (e.g. zbud, zsmalloc)
 134  * @name:       The name of the zpool (e.g. zram0, zswap)
 135  * @gfp:        The GFP flags to use when allocating the pool.
 136  *
 137  * This creates a new zpool of the specified type.  The gfp flags will be
 138  * used when allocating memory, if the implementation supports it.  If the
 139  * ops param is NULL, then the created zpool will not be evictable.
 140  *
 141  * Implementations must guarantee this to be thread-safe.
 142  *
 143  * The @type and @name strings must be null-terminated.
 144  *
 145  * Returns: New zpool on success, NULL on failure.
 146  */
 147 struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp)
 148 {
 149         struct zpool_driver *driver;
 150         struct zpool *zpool;
 151
 152         pr_debug("creating pool type %s\n", type);
 153
 154         driver = zpool_get_driver(type);
 155
 156         if (!driver) {
 157                 request_module("zpool-%s", type);
 158                 driver = zpool_get_driver(type);
 159         }
 160
 161         if (!driver) {
 162                 pr_err("no driver for type %s\n", type);
 163                 return NULL;
 164         }
 165
 166         zpool = kmalloc(sizeof(*zpool), gfp);
 167         if (!zpool) {
 168                 pr_err("couldn't create zpool - out of memory\n");
 169                 zpool_put_driver(driver);
 170                 return NULL;
 171         }
 172
 173         zpool->driver = driver;
 174         zpool->pool = driver->create(name, gfp);
 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_debug("created pool type %s\n", type);
 184
 185         return zpool;
 186 }
 187
 188 /**
 189  * zpool_destroy_pool() - Destroy a zpool
 190  * @zpool:      The zpool to destroy.
 191  *
 192  * Implementations must guarantee this to be thread-safe,
 193  * however only when destroying different pools.  The same
 194  * pool should only be destroyed once, and should not be used
 195  * after it is destroyed.
 196  *
 197  * This destroys an existing zpool.  The zpool should not be in use.
 198  */
 199 void zpool_destroy_pool(struct zpool *zpool)
 200 {
 201         pr_debug("destroying pool type %s\n", zpool->driver->type);
 202
 203         zpool->driver->destroy(zpool->pool);
 204         zpool_put_driver(zpool->driver);
 205         kfree(zpool);
 206 }
 207
 208 /**
 209  * zpool_get_type() - Get the type of the zpool
 210  * @zpool:      The zpool to check
 211  *
 212  * This returns the type of the pool.
 213  *
 214  * Implementations must guarantee this to be thread-safe.
 215  *
 216  * Returns: The type of zpool.
 217  */
 218 const char *zpool_get_type(struct zpool *zpool)
 219 {
 220         return zpool->driver->type;
 221 }
 222
 223 /**
 224  * zpool_malloc_support_movable() - Check if the zpool supports
 225  *      allocating movable memory
 226  * @zpool:      The zpool to check
 227  *
 228  * This returns if the zpool supports allocating movable memory.
 229  *
 230  * Implementations must guarantee this to be thread-safe.
 231  *
 232  * Returns: true if the zpool supports allocating movable memory, false if not
 233  */
 234 bool zpool_malloc_support_movable(struct zpool *zpool)
 235 {
 236         return zpool->driver->malloc_support_movable;
 237 }
 238
 239 /**
 240  * zpool_malloc() - Allocate memory
 241  * @zpool:      The zpool to allocate from.
 242  * @size:       The amount of memory to allocate.
 243  * @gfp:        The GFP flags to use when allocating memory.
 244  * @handle:     Pointer to the handle to set
 245  *
 246  * This allocates the requested amount of memory from the pool.
 247  * The gfp flags will be used when allocating memory, if the
 248  * implementation supports it.  The provided @handle will be
 249  * set to the allocated object handle.
 250  *
 251  * Implementations must guarantee this to be thread-safe.
 252  *
 253  * Returns: 0 on success, negative value on error.
 254  */
 255 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
 256                         unsigned long *handle)
 257 {
 258         return zpool->driver->malloc(zpool->pool, size, gfp, handle);
 259 }
 260
 261 /**
 262  * zpool_free() - Free previously allocated memory
 263  * @zpool:      The zpool that allocated the memory.
 264  * @handle:     The handle to the memory to free.
 265  *
 266  * This frees previously allocated memory.  This does not guarantee
 267  * that the pool will actually free memory, only that the memory
 268  * in the pool will become available for use by the pool.
 269  *
 270  * Implementations must guarantee this to be thread-safe,
 271  * however only when freeing different handles.  The same
 272  * handle should only be freed once, and should not be used
 273  * after freeing.
 274  */
 275 void zpool_free(struct zpool *zpool, unsigned long handle)
 276 {
 277         zpool->driver->free(zpool->pool, handle);
 278 }
 279
 280 /**
 281  * zpool_map_handle() - Map a previously allocated handle into memory
 282  * @zpool:      The zpool that the handle was allocated from
 283  * @handle:     The handle to map
 284  * @mapmode:    How the memory should be mapped
 285  *
 286  * This maps a previously allocated handle into memory.  The @mapmode
 287  * param indicates to the implementation how the memory will be
 288  * used, i.e. read-only, write-only, read-write.  If the
 289  * implementation does not support it, the memory will be treated
 290  * as read-write.
 291  *
 292  * This may hold locks, disable interrupts, and/or preemption,
 293  * and the zpool_unmap_handle() must be called to undo those
 294  * actions.  The code that uses the mapped handle should complete
 295  * its operations on the mapped handle memory quickly and unmap
 296  * as soon as possible.  As the implementation may use per-cpu
 297  * data, multiple handles should not be mapped concurrently on
 298  * any cpu.
 299  *
 300  * Returns: A pointer to the handle's mapped memory area.
 301  */
 302 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
 303                         enum zpool_mapmode mapmode)
 304 {
 305         return zpool->driver->map(zpool->pool, handle, mapmode);
 306 }
 307
 308 /**
 309  * zpool_unmap_handle() - Unmap a previously mapped handle
 310  * @zpool:      The zpool that the handle was allocated from
 311  * @handle:     The handle to unmap
 312  *
 313  * This unmaps a previously mapped handle.  Any locks or other
 314  * actions that the implementation took in zpool_map_handle()
 315  * will be undone here.  The memory area returned from
 316  * zpool_map_handle() should no longer be used after this.
 317  */
 318 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
 319 {
 320         zpool->driver->unmap(zpool->pool, handle);
 321 }
 322
 323 /**
 324  * zpool_get_total_pages() - The total size of the pool
 325  * @zpool:      The zpool to check
 326  *
 327  * This returns the total size in pages of the pool.
 328  *
 329  * Returns: Total size of the zpool in pages.
 330  */
 331 u64 zpool_get_total_pages(struct zpool *zpool)
 332 {
 333         return zpool->driver->total_pages(zpool->pool);
 334 }
 335
 336 /**
 337  * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
 338  * @zpool:      The zpool to test
 339  *
 340  * Some allocators enter non-preemptible context in ->map() callback (e.g.
 341  * disable pagefaults) and exit that context in ->unmap(), which limits what
 342  * we can do with the mapped object. For instance, we cannot wait for
 343  * asynchronous crypto API to decompress such an object or take mutexes
 344  * since those will call into the scheduler. This function tells us whether
 345  * we use such an allocator.
 346  *
 347  * Returns: true if zpool can sleep; false otherwise.
 348  */
 349 bool zpool_can_sleep_mapped(struct zpool *zpool)
 350 {
 351         return zpool->driver->sleep_mapped;
 352 }
 353
 354 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
 355 MODULE_DESCRIPTION("Common API for compressed memory storage");