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![Dan Streetman](/assets/img/avatar_default.png)
This series makes creation of the zpool and compressor dynamic, so that they can be changed at runtime. This makes using/configuring zswap easier, as before this zswap had to be configured at boot time, using boot params. This uses a single list to track both the zpool and compressor together, although Seth had mentioned an alternative which is to track the zpools and compressors using separate lists. In the most common case, only a single zpool and single compressor, using one list is slightly simpler than using two lists, and for the uncommon case of multiple zpools and/or compressors, using one list is slightly less simple (and uses slightly more memory, probably) than using two lists. This patch (of 4): Add zpool_has_pool() function, indicating if the specified type of zpool is available (i.e. zsmalloc or zbud). This allows checking if a pool is available, without actually trying to allocate it, similar to crypto_has_alg(). This is used by a following patch to zswap that enables the dynamic runtime creation of zswap zpools. Signed-off-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Seth Jennings <sjennings@variantweb.net> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
358 lines
9.9 KiB
C
358 lines
9.9 KiB
C
/*
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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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char *type;
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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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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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static struct zpool_driver *zpool_get_driver(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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* 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 shrinkable.
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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: New zpool on success, NULL on failure.
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*/
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struct zpool *zpool_create_pool(char *type, 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->type = driver->type;
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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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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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* @pool 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->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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* @pool 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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char *zpool_get_type(struct zpool *zpool)
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{
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return zpool->type;
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}
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/**
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* zpool_malloc() - Allocate memory
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* @pool 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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* @pool 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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* @pool 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(zpool->pool, pages, reclaimed);
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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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* @pool The zpool that the handle was allocated from
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* @handle The handle to map
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* @mm How the memory should be mapped
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*
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* This maps a previously allocated handle into memory. The @mm
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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 operatons 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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* @pool 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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* @pool 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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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
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MODULE_DESCRIPTION("Common API for compressed memory storage");
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