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- /*
- * zpool memory storage api
- *
- * Copyright (C) 2014 Dan Streetman
- *
- * This is a common frontend for memory storage pool implementations.
- * Typically, this is used to store compressed memory.
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/list.h>
- #include <linux/types.h>
- #include <linux/mm.h>
- #include <linux/slab.h>
- #include <linux/spinlock.h>
- #include <linux/module.h>
- #include <linux/zpool.h>
- struct zpool {
- struct zpool_driver *driver;
- void *pool;
- const struct zpool_ops *ops;
- struct list_head list;
- };
- static LIST_HEAD(drivers_head);
- static DEFINE_SPINLOCK(drivers_lock);
- static LIST_HEAD(pools_head);
- static DEFINE_SPINLOCK(pools_lock);
- /**
- * zpool_register_driver() - register a zpool implementation.
- * @driver: driver to register
- */
- void zpool_register_driver(struct zpool_driver *driver)
- {
- spin_lock(&drivers_lock);
- atomic_set(&driver->refcount, 0);
- list_add(&driver->list, &drivers_head);
- spin_unlock(&drivers_lock);
- }
- EXPORT_SYMBOL(zpool_register_driver);
- /**
- * zpool_unregister_driver() - unregister a zpool implementation.
- * @driver: driver to unregister.
- *
- * Module usage counting is used to prevent using a driver
- * while/after unloading, so if this is called from module
- * exit function, this should never fail; if called from
- * other than the module exit function, and this returns
- * failure, the driver is in use and must remain available.
- */
- int zpool_unregister_driver(struct zpool_driver *driver)
- {
- int ret = 0, refcount;
- spin_lock(&drivers_lock);
- refcount = atomic_read(&driver->refcount);
- WARN_ON(refcount < 0);
- if (refcount > 0)
- ret = -EBUSY;
- else
- list_del(&driver->list);
- spin_unlock(&drivers_lock);
- return ret;
- }
- EXPORT_SYMBOL(zpool_unregister_driver);
- /* this assumes @type is null-terminated. */
- static struct zpool_driver *zpool_get_driver(const char *type)
- {
- struct zpool_driver *driver;
- spin_lock(&drivers_lock);
- list_for_each_entry(driver, &drivers_head, list) {
- if (!strcmp(driver->type, type)) {
- bool got = try_module_get(driver->owner);
- if (got)
- atomic_inc(&driver->refcount);
- spin_unlock(&drivers_lock);
- return got ? driver : NULL;
- }
- }
- spin_unlock(&drivers_lock);
- return NULL;
- }
- static void zpool_put_driver(struct zpool_driver *driver)
- {
- atomic_dec(&driver->refcount);
- module_put(driver->owner);
- }
- /**
- * zpool_has_pool() - Check if the pool driver is available
- * @type The type of the zpool to check (e.g. zbud, zsmalloc)
- *
- * This checks if the @type pool driver is available. This will try to load
- * the requested module, if needed, but there is no guarantee the module will
- * still be loaded and available immediately after calling. If this returns
- * true, the caller should assume the pool is available, but must be prepared
- * to handle the @zpool_create_pool() returning failure. However if this
- * returns false, the caller should assume the requested pool type is not
- * available; either the requested pool type module does not exist, or could
- * not be loaded, and calling @zpool_create_pool() with the pool type will
- * fail.
- *
- * The @type string must be null-terminated.
- *
- * Returns: true if @type pool is available, false if not
- */
- bool zpool_has_pool(char *type)
- {
- struct zpool_driver *driver = zpool_get_driver(type);
- if (!driver) {
- request_module("zpool-%s", type);
- driver = zpool_get_driver(type);
- }
- if (!driver)
- return false;
- zpool_put_driver(driver);
- return true;
- }
- EXPORT_SYMBOL(zpool_has_pool);
- /**
- * zpool_create_pool() - Create a new zpool
- * @type The type of the zpool to create (e.g. zbud, zsmalloc)
- * @name The name of the zpool (e.g. zram0, zswap)
- * @gfp The GFP flags to use when allocating the pool.
- * @ops The optional ops callback.
- *
- * This creates a new zpool of the specified type. The gfp flags will be
- * used when allocating memory, if the implementation supports it. If the
- * ops param is NULL, then the created zpool will not be shrinkable.
- *
- * Implementations must guarantee this to be thread-safe.
- *
- * The @type and @name strings must be null-terminated.
- *
- * Returns: New zpool on success, NULL on failure.
- */
- struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
- const struct zpool_ops *ops)
- {
- struct zpool_driver *driver;
- struct zpool *zpool;
- pr_debug("creating pool type %s\n", type);
- driver = zpool_get_driver(type);
- if (!driver) {
- request_module("zpool-%s", type);
- driver = zpool_get_driver(type);
- }
- if (!driver) {
- pr_err("no driver for type %s\n", type);
- return NULL;
- }
- zpool = kmalloc(sizeof(*zpool), gfp);
- if (!zpool) {
- pr_err("couldn't create zpool - out of memory\n");
- zpool_put_driver(driver);
- return NULL;
- }
- zpool->driver = driver;
- zpool->pool = driver->create(name, gfp, ops, zpool);
- zpool->ops = ops;
- if (!zpool->pool) {
- pr_err("couldn't create %s pool\n", type);
- zpool_put_driver(driver);
- kfree(zpool);
- return NULL;
- }
- pr_debug("created pool type %s\n", type);
- spin_lock(&pools_lock);
- list_add(&zpool->list, &pools_head);
- spin_unlock(&pools_lock);
- return zpool;
- }
- /**
- * zpool_destroy_pool() - Destroy a zpool
- * @pool The zpool to destroy.
- *
- * Implementations must guarantee this to be thread-safe,
- * however only when destroying different pools. The same
- * pool should only be destroyed once, and should not be used
- * after it is destroyed.
- *
- * This destroys an existing zpool. The zpool should not be in use.
- */
- void zpool_destroy_pool(struct zpool *zpool)
- {
- pr_debug("destroying pool type %s\n", zpool->driver->type);
- spin_lock(&pools_lock);
- list_del(&zpool->list);
- spin_unlock(&pools_lock);
- zpool->driver->destroy(zpool->pool);
- zpool_put_driver(zpool->driver);
- kfree(zpool);
- }
- /**
- * zpool_get_type() - Get the type of the zpool
- * @pool The zpool to check
- *
- * This returns the type of the pool.
- *
- * Implementations must guarantee this to be thread-safe.
- *
- * Returns: The type of zpool.
- */
- const char *zpool_get_type(struct zpool *zpool)
- {
- return zpool->driver->type;
- }
- /**
- * zpool_malloc() - Allocate memory
- * @pool The zpool to allocate from.
- * @size The amount of memory to allocate.
- * @gfp The GFP flags to use when allocating memory.
- * @handle Pointer to the handle to set
- *
- * This allocates the requested amount of memory from the pool.
- * The gfp flags will be used when allocating memory, if the
- * implementation supports it. The provided @handle will be
- * set to the allocated object handle.
- *
- * Implementations must guarantee this to be thread-safe.
- *
- * Returns: 0 on success, negative value on error.
- */
- int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
- unsigned long *handle)
- {
- return zpool->driver->malloc(zpool->pool, size, gfp, handle);
- }
- /**
- * zpool_free() - Free previously allocated memory
- * @pool The zpool that allocated the memory.
- * @handle The handle to the memory to free.
- *
- * This frees previously allocated memory. This does not guarantee
- * that the pool will actually free memory, only that the memory
- * in the pool will become available for use by the pool.
- *
- * Implementations must guarantee this to be thread-safe,
- * however only when freeing different handles. The same
- * handle should only be freed once, and should not be used
- * after freeing.
- */
- void zpool_free(struct zpool *zpool, unsigned long handle)
- {
- zpool->driver->free(zpool->pool, handle);
- }
- /**
- * zpool_shrink() - Shrink the pool size
- * @pool The zpool to shrink.
- * @pages The number of pages to shrink the pool.
- * @reclaimed The number of pages successfully evicted.
- *
- * This attempts to shrink the actual memory size of the pool
- * by evicting currently used handle(s). If the pool was
- * created with no zpool_ops, or the evict call fails for any
- * of the handles, this will fail. If non-NULL, the @reclaimed
- * parameter will be set to the number of pages reclaimed,
- * which may be more than the number of pages requested.
- *
- * Implementations must guarantee this to be thread-safe.
- *
- * Returns: 0 on success, negative value on error/failure.
- */
- int zpool_shrink(struct zpool *zpool, unsigned int pages,
- unsigned int *reclaimed)
- {
- return zpool->driver->shrink(zpool->pool, pages, reclaimed);
- }
- /**
- * zpool_map_handle() - Map a previously allocated handle into memory
- * @pool The zpool that the handle was allocated from
- * @handle The handle to map
- * @mm How the memory should be mapped
- *
- * This maps a previously allocated handle into memory. The @mm
- * param indicates to the implementation how the memory will be
- * used, i.e. read-only, write-only, read-write. If the
- * implementation does not support it, the memory will be treated
- * as read-write.
- *
- * This may hold locks, disable interrupts, and/or preemption,
- * and the zpool_unmap_handle() must be called to undo those
- * actions. The code that uses the mapped handle should complete
- * its operatons on the mapped handle memory quickly and unmap
- * as soon as possible. As the implementation may use per-cpu
- * data, multiple handles should not be mapped concurrently on
- * any cpu.
- *
- * Returns: A pointer to the handle's mapped memory area.
- */
- void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
- enum zpool_mapmode mapmode)
- {
- return zpool->driver->map(zpool->pool, handle, mapmode);
- }
- /**
- * zpool_unmap_handle() - Unmap a previously mapped handle
- * @pool The zpool that the handle was allocated from
- * @handle The handle to unmap
- *
- * This unmaps a previously mapped handle. Any locks or other
- * actions that the implementation took in zpool_map_handle()
- * will be undone here. The memory area returned from
- * zpool_map_handle() should no longer be used after this.
- */
- void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
- {
- zpool->driver->unmap(zpool->pool, handle);
- }
- /**
- * zpool_get_total_size() - The total size of the pool
- * @pool The zpool to check
- *
- * This returns the total size in bytes of the pool.
- *
- * Returns: Total size of the zpool in bytes.
- */
- u64 zpool_get_total_size(struct zpool *zpool)
- {
- return zpool->driver->total_size(zpool->pool);
- }
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
- MODULE_DESCRIPTION("Common API for compressed memory storage");
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