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Diffstat (limited to '')
-rw-r--r-- | mm/zpool.c | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/mm/zpool.c b/mm/zpool.c new file mode 100644 index 000000000..3744a2d1a --- /dev/null +++ b/mm/zpool.c @@ -0,0 +1,398 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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; + bool evictable; + + 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 evictable. + * + * 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; + zpool->evictable = driver->shrink && ops && ops->evict; + + 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 + * @zpool: 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 + * @zpool: 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_support_movable() - Check if the zpool supports + * allocating movable memory + * @zpool: The zpool to check + * + * This returns if the zpool supports allocating movable memory. + * + * Implementations must guarantee this to be thread-safe. + * + * Returns: true if the zpool supports allocating movable memory, false if not + */ +bool zpool_malloc_support_movable(struct zpool *zpool) +{ + return zpool->driver->malloc_support_movable; +} + +/** + * zpool_malloc() - Allocate memory + * @zpool: 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 + * @zpool: 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 + * @zpool: 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->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL; +} + +/** + * zpool_map_handle() - Map a previously allocated handle into memory + * @zpool: The zpool that the handle was allocated from + * @handle: The handle to map + * @mapmode: How the memory should be mapped + * + * This maps a previously allocated handle into memory. The @mapmode + * 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 + * @zpool: 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 + * @zpool: 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); +} + +/** + * zpool_evictable() - Test if zpool is potentially evictable + * @zpool: The zpool to test + * + * Zpool is only potentially evictable when it's created with struct + * zpool_ops.evict and its driver implements struct zpool_driver.shrink. + * + * However, it doesn't necessarily mean driver will use zpool_ops.evict + * in its implementation of zpool_driver.shrink. It could do internal + * defragmentation instead. + * + * Returns: true if potentially evictable; false otherwise. + */ +bool zpool_evictable(struct zpool *zpool) +{ + return zpool->evictable; +} + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>"); +MODULE_DESCRIPTION("Common API for compressed memory storage"); |