/*
* 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");
