/* * 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() - 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");