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411 lines
12 KiB
411 lines
12 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* zpool memory storage api |
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* |
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* Copyright (C) 2014 Dan Streetman |
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* |
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* This is a common frontend for memory storage pool implementations. |
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* Typically, this is used to store compressed memory. |
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*/ |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/list.h> |
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#include <linux/types.h> |
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#include <linux/mm.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/module.h> |
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#include <linux/zpool.h> |
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struct zpool { |
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struct zpool_driver *driver; |
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void *pool; |
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const struct zpool_ops *ops; |
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bool evictable; |
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bool can_sleep_mapped; |
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struct list_head list; |
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}; |
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static LIST_HEAD(drivers_head); |
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static DEFINE_SPINLOCK(drivers_lock); |
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static LIST_HEAD(pools_head); |
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static DEFINE_SPINLOCK(pools_lock); |
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/** |
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* zpool_register_driver() - register a zpool implementation. |
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* @driver: driver to register |
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*/ |
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void zpool_register_driver(struct zpool_driver *driver) |
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{ |
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spin_lock(&drivers_lock); |
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atomic_set(&driver->refcount, 0); |
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list_add(&driver->list, &drivers_head); |
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spin_unlock(&drivers_lock); |
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} |
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EXPORT_SYMBOL(zpool_register_driver); |
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/** |
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* zpool_unregister_driver() - unregister a zpool implementation. |
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* @driver: driver to unregister. |
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* |
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* Module usage counting is used to prevent using a driver |
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* while/after unloading, so if this is called from module |
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* exit function, this should never fail; if called from |
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* other than the module exit function, and this returns |
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* failure, the driver is in use and must remain available. |
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*/ |
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int zpool_unregister_driver(struct zpool_driver *driver) |
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{ |
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int ret = 0, refcount; |
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spin_lock(&drivers_lock); |
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refcount = atomic_read(&driver->refcount); |
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WARN_ON(refcount < 0); |
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if (refcount > 0) |
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ret = -EBUSY; |
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else |
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list_del(&driver->list); |
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spin_unlock(&drivers_lock); |
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return ret; |
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} |
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EXPORT_SYMBOL(zpool_unregister_driver); |
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/* this assumes @type is null-terminated. */ |
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static struct zpool_driver *zpool_get_driver(const char *type) |
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{ |
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struct zpool_driver *driver; |
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spin_lock(&drivers_lock); |
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list_for_each_entry(driver, &drivers_head, list) { |
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if (!strcmp(driver->type, type)) { |
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bool got = try_module_get(driver->owner); |
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if (got) |
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atomic_inc(&driver->refcount); |
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spin_unlock(&drivers_lock); |
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return got ? driver : NULL; |
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} |
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} |
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spin_unlock(&drivers_lock); |
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return NULL; |
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} |
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static void zpool_put_driver(struct zpool_driver *driver) |
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{ |
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atomic_dec(&driver->refcount); |
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module_put(driver->owner); |
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} |
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/** |
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* zpool_has_pool() - Check if the pool driver is available |
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* @type: The type of the zpool to check (e.g. zbud, zsmalloc) |
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* |
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* This checks if the @type pool driver is available. This will try to load |
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* the requested module, if needed, but there is no guarantee the module will |
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* still be loaded and available immediately after calling. If this returns |
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* true, the caller should assume the pool is available, but must be prepared |
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* to handle the @zpool_create_pool() returning failure. However if this |
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* returns false, the caller should assume the requested pool type is not |
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* available; either the requested pool type module does not exist, or could |
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* not be loaded, and calling @zpool_create_pool() with the pool type will |
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* fail. |
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* |
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* The @type string must be null-terminated. |
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* |
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* Returns: true if @type pool is available, false if not |
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*/ |
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bool zpool_has_pool(char *type) |
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{ |
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struct zpool_driver *driver = zpool_get_driver(type); |
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if (!driver) { |
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request_module("zpool-%s", type); |
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driver = zpool_get_driver(type); |
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} |
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if (!driver) |
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return false; |
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zpool_put_driver(driver); |
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return true; |
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} |
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EXPORT_SYMBOL(zpool_has_pool); |
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/** |
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* zpool_create_pool() - Create a new zpool |
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* @type: The type of the zpool to create (e.g. zbud, zsmalloc) |
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* @name: The name of the zpool (e.g. zram0, zswap) |
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* @gfp: The GFP flags to use when allocating the pool. |
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* @ops: The optional ops callback. |
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* |
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* This creates a new zpool of the specified type. The gfp flags will be |
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* used when allocating memory, if the implementation supports it. If the |
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* ops param is NULL, then the created zpool will not be evictable. |
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* |
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* Implementations must guarantee this to be thread-safe. |
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* |
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* The @type and @name strings must be null-terminated. |
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* |
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* Returns: New zpool on success, NULL on failure. |
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*/ |
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struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp, |
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const struct zpool_ops *ops) |
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{ |
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struct zpool_driver *driver; |
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struct zpool *zpool; |
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pr_debug("creating pool type %s\n", type); |
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driver = zpool_get_driver(type); |
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if (!driver) { |
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request_module("zpool-%s", type); |
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driver = zpool_get_driver(type); |
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} |
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if (!driver) { |
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pr_err("no driver for type %s\n", type); |
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return NULL; |
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} |
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zpool = kmalloc(sizeof(*zpool), gfp); |
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if (!zpool) { |
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pr_err("couldn't create zpool - out of memory\n"); |
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zpool_put_driver(driver); |
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return NULL; |
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} |
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zpool->driver = driver; |
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zpool->pool = driver->create(name, gfp, ops, zpool); |
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zpool->ops = ops; |
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zpool->evictable = driver->shrink && ops && ops->evict; |
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zpool->can_sleep_mapped = driver->sleep_mapped; |
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if (!zpool->pool) { |
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pr_err("couldn't create %s pool\n", type); |
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zpool_put_driver(driver); |
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kfree(zpool); |
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return NULL; |
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} |
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pr_debug("created pool type %s\n", type); |
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spin_lock(&pools_lock); |
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list_add(&zpool->list, &pools_head); |
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spin_unlock(&pools_lock); |
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return zpool; |
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} |
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/** |
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* zpool_destroy_pool() - Destroy a zpool |
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* @zpool: The zpool to destroy. |
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* |
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* Implementations must guarantee this to be thread-safe, |
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* however only when destroying different pools. The same |
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* pool should only be destroyed once, and should not be used |
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* after it is destroyed. |
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* |
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* This destroys an existing zpool. The zpool should not be in use. |
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*/ |
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void zpool_destroy_pool(struct zpool *zpool) |
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{ |
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pr_debug("destroying pool type %s\n", zpool->driver->type); |
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spin_lock(&pools_lock); |
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list_del(&zpool->list); |
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spin_unlock(&pools_lock); |
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zpool->driver->destroy(zpool->pool); |
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zpool_put_driver(zpool->driver); |
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kfree(zpool); |
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} |
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/** |
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* zpool_get_type() - Get the type of the zpool |
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* @zpool: The zpool to check |
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* |
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* This returns the type of the pool. |
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* |
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* Implementations must guarantee this to be thread-safe. |
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* |
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* Returns: The type of zpool. |
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*/ |
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const char *zpool_get_type(struct zpool *zpool) |
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{ |
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return zpool->driver->type; |
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} |
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/** |
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* zpool_malloc_support_movable() - Check if the zpool supports |
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* allocating movable memory |
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* @zpool: The zpool to check |
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* |
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* This returns if the zpool supports allocating movable memory. |
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* |
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* Implementations must guarantee this to be thread-safe. |
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* |
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* Returns: true if the zpool supports allocating movable memory, false if not |
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*/ |
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bool zpool_malloc_support_movable(struct zpool *zpool) |
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{ |
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return zpool->driver->malloc_support_movable; |
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} |
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/** |
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* zpool_malloc() - Allocate memory |
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* @zpool: The zpool to allocate from. |
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* @size: The amount of memory to allocate. |
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* @gfp: The GFP flags to use when allocating memory. |
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* @handle: Pointer to the handle to set |
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* |
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* This allocates the requested amount of memory from the pool. |
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* The gfp flags will be used when allocating memory, if the |
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* implementation supports it. The provided @handle will be |
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* set to the allocated object handle. |
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* |
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* Implementations must guarantee this to be thread-safe. |
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* |
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* Returns: 0 on success, negative value on error. |
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*/ |
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int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp, |
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unsigned long *handle) |
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{ |
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return zpool->driver->malloc(zpool->pool, size, gfp, handle); |
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} |
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/** |
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* zpool_free() - Free previously allocated memory |
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* @zpool: The zpool that allocated the memory. |
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* @handle: The handle to the memory to free. |
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* |
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* This frees previously allocated memory. This does not guarantee |
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* that the pool will actually free memory, only that the memory |
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* in the pool will become available for use by the pool. |
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* |
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* Implementations must guarantee this to be thread-safe, |
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* however only when freeing different handles. The same |
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* handle should only be freed once, and should not be used |
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* after freeing. |
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*/ |
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void zpool_free(struct zpool *zpool, unsigned long handle) |
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{ |
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zpool->driver->free(zpool->pool, handle); |
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} |
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/** |
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* zpool_shrink() - Shrink the pool size |
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* @zpool: The zpool to shrink. |
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* @pages: The number of pages to shrink the pool. |
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* @reclaimed: The number of pages successfully evicted. |
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* |
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* This attempts to shrink the actual memory size of the pool |
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* by evicting currently used handle(s). If the pool was |
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* created with no zpool_ops, or the evict call fails for any |
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* of the handles, this will fail. If non-NULL, the @reclaimed |
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* parameter will be set to the number of pages reclaimed, |
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* which may be more than the number of pages requested. |
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* |
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* Implementations must guarantee this to be thread-safe. |
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* |
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* Returns: 0 on success, negative value on error/failure. |
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*/ |
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int zpool_shrink(struct zpool *zpool, unsigned int pages, |
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unsigned int *reclaimed) |
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{ |
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return zpool->driver->shrink ? |
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zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL; |
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} |
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/** |
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* zpool_map_handle() - Map a previously allocated handle into memory |
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* @zpool: The zpool that the handle was allocated from |
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* @handle: The handle to map |
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* @mapmode: How the memory should be mapped |
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* |
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* This maps a previously allocated handle into memory. The @mapmode |
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* param indicates to the implementation how the memory will be |
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* used, i.e. read-only, write-only, read-write. If the |
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* implementation does not support it, the memory will be treated |
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* as read-write. |
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* |
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* This may hold locks, disable interrupts, and/or preemption, |
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* and the zpool_unmap_handle() must be called to undo those |
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* actions. The code that uses the mapped handle should complete |
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* its operations on the mapped handle memory quickly and unmap |
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* as soon as possible. As the implementation may use per-cpu |
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* data, multiple handles should not be mapped concurrently on |
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* any cpu. |
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* |
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* Returns: A pointer to the handle's mapped memory area. |
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*/ |
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void *zpool_map_handle(struct zpool *zpool, unsigned long handle, |
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enum zpool_mapmode mapmode) |
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{ |
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return zpool->driver->map(zpool->pool, handle, mapmode); |
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} |
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/** |
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* zpool_unmap_handle() - Unmap a previously mapped handle |
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* @zpool: The zpool that the handle was allocated from |
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* @handle: The handle to unmap |
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* |
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* This unmaps a previously mapped handle. Any locks or other |
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* actions that the implementation took in zpool_map_handle() |
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* will be undone here. The memory area returned from |
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* zpool_map_handle() should no longer be used after this. |
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*/ |
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void zpool_unmap_handle(struct zpool *zpool, unsigned long handle) |
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{ |
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zpool->driver->unmap(zpool->pool, handle); |
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} |
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/** |
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* zpool_get_total_size() - The total size of the pool |
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* @zpool: The zpool to check |
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* |
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* This returns the total size in bytes of the pool. |
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* |
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* Returns: Total size of the zpool in bytes. |
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*/ |
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u64 zpool_get_total_size(struct zpool *zpool) |
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{ |
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return zpool->driver->total_size(zpool->pool); |
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} |
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/** |
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* zpool_evictable() - Test if zpool is potentially evictable |
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* @zpool: The zpool to test |
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* |
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* Zpool is only potentially evictable when it's created with struct |
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* zpool_ops.evict and its driver implements struct zpool_driver.shrink. |
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* |
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* However, it doesn't necessarily mean driver will use zpool_ops.evict |
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* in its implementation of zpool_driver.shrink. It could do internal |
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* defragmentation instead. |
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* |
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* Returns: true if potentially evictable; false otherwise. |
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*/ |
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bool zpool_evictable(struct zpool *zpool) |
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{ |
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return zpool->evictable; |
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} |
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/** |
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* zpool_can_sleep_mapped - Test if zpool can sleep when do mapped. |
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* @zpool: The zpool to test |
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* |
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* Returns: true if zpool can sleep; false otherwise. |
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*/ |
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bool zpool_can_sleep_mapped(struct zpool *zpool) |
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{ |
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return zpool->can_sleep_mapped; |
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} |
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MODULE_LICENSE("GPL"); |
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MODULE_AUTHOR("Dan Streetman <[email protected]>"); |
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MODULE_DESCRIPTION("Common API for compressed memory storage");
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