1 files changed, 381 insertions, 0 deletions
diff --git a/mm/zpool.c b/mm/zpool.c
new file mode 100644
index 000000000..01a771e30
--- /dev/null
+++ b/mm/zpool.c
@@ -0,0 +1,381 @@
+/*
+ * 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");