mm/zpool: implement common zpool api to zbud/zsmalloc

Add zpool api.

zpool provides an interface for memory storage, typically of compressed
memory.  Users can select what backend to use; currently the only
implementations are zbud, a low density implementation with up to two
compressed pages per storage page, and zsmalloc, a higher density
implementation with multiple compressed pages per storage page.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Tested-by: Seth Jennings <sjennings@variantweb.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Weijie Yang <weijie.yang@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 389 insertions, 18 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index f4899ec39cf4..12179b8c3b89 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -519,15 +519,17 @@ config CMA_AREAS
 
           If unsure, leave the default value "7".
 
-config ZBUD
-        tristate
-        default n
+config MEM_SOFT_DIRTY
+        bool "Track memory changes"
+        depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
+        select PROC_PAGE_MONITOR
         help
-          A special purpose allocator for storing compressed pages.
-          It is designed to store up to two compressed pages per physical
-          page.  While this design limits storage density, it has simple and
-          deterministic reclaim properties that make it preferable to a higher
-          density approach when reclaim will be used.
+          This option enables memory changes tracking by introducing a
+          soft-dirty bit on pte-s. This bit it set when someone writes
+          into a page just as regular dirty bit, but unlike the latter
+          it can be cleared by hands.
+
+          See Documentation/vm/soft-dirty.txt for more details.
 
 config ZSWAP
         bool "Compressed cache for swap pages (EXPERIMENTAL)"
@@ -549,17 +551,22 @@ config ZSWAP
           they have not be fully explored on the large set of potential
           configurations and workloads that exist.
 
-config MEM_SOFT_DIRTY
-        bool "Track memory changes"
-        depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
-        select PROC_PAGE_MONITOR
+config ZPOOL
+        tristate "Common API for compressed memory storage"
+        default n
         help
-          This option enables memory changes tracking by introducing a
-          soft-dirty bit on pte-s. This bit it set when someone writes
-          into a page just as regular dirty bit, but unlike the latter
-          it can be cleared by hands.
+          Compressed memory storage API.  This allows using either zbud or
+          zsmalloc.
 
-          See Documentation/vm/soft-dirty.txt for more details.
+config ZBUD
+        tristate "Low density storage for compressed pages"
+        default n
+        help
+          A special purpose allocator for storing compressed pages.
+          It is designed to store up to two compressed pages per physical
+          page.  While this design limits storage density, it has simple and
+          deterministic reclaim properties that make it preferable to a higher
+          density approach when reclaim will be used.
 
 config ZSMALLOC
         tristate "Memory allocator for compressed pages"
diff --git a/mm/Makefile b/mm/Makefile
index 8338473c329a..632ae77e6070 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
 obj-$(CONFIG_CLEANCACHE) += cleancache.o
 obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
+obj-$(CONFIG_ZPOOL)     += zpool.o
 obj-$(CONFIG_ZBUD)      += zbud.o
 obj-$(CONFIG_ZSMALLOC)  += zsmalloc.o
 obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
diff --git a/mm/zpool.c b/mm/zpool.c
new file mode 100644
index 000000000000..e40612a1df00
--- /dev/null
+++ b/mm/zpool.c
@@ -0,0 +1,364 @@
+/*
+ * 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 {
+        char *type;
+
+        struct zpool_driver *driver;
+        void *pool;
+        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);
+
+/**
+ * zpool_evict() - evict callback from a zpool implementation.
+ * @pool:       pool to evict from.
+ * @handle:     handle to evict.
+ *
+ * This can be used by zpool implementations to call the
+ * user's evict zpool_ops struct evict callback.
+ */
+int zpool_evict(void *pool, unsigned long handle)
+{
+        struct zpool *zpool;
+
+        spin_lock(&pools_lock);
+        list_for_each_entry(zpool, &pools_head, list) {
+                if (zpool->pool == pool) {
+                        spin_unlock(&pools_lock);
+                        if (!zpool->ops || !zpool->ops->evict)
+                                return -EINVAL;
+                        return zpool->ops->evict(zpool, handle);
+                }
+        }
+        spin_unlock(&pools_lock);
+
+        return -ENOENT;
+}
+EXPORT_SYMBOL(zpool_evict);
+
+static struct zpool_driver *zpool_get_driver(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_create_pool() - Create a new zpool
+ * @type        The type of the zpool to create (e.g. zbud, zsmalloc)
+ * @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.
+ *
+ * Returns: New zpool on success, NULL on failure.
+ */
+struct zpool *zpool_create_pool(char *type, gfp_t gfp, struct zpool_ops *ops)
+{
+        struct zpool_driver *driver;
+        struct zpool *zpool;
+
+        pr_info("creating pool type %s\n", type);
+
+        driver = zpool_get_driver(type);
+
+        if (!driver) {
+                request_module(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->type = driver->type;
+        zpool->driver = driver;
+        zpool->pool = driver->create(gfp, ops);
+        zpool->ops = ops;
+
+        if (!zpool->pool) {
+                pr_err("couldn't create %s pool\n", type);
+                zpool_put_driver(driver);
+                kfree(zpool);
+                return NULL;
+        }
+
+        pr_info("created %s pool\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_info("destroying pool type %s\n", zpool->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.
+ */
+char *zpool_get_type(struct zpool *zpool)
+{
+        return zpool->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);
+}
+
+static int __init init_zpool(void)
+{
+        pr_info("loaded\n");
+        return 0;
+}
+
+static void __exit exit_zpool(void)
+{
+        pr_info("unloaded\n");
+}
+
+module_init(init_zpool);
+module_exit(exit_zpool);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
+MODULE_DESCRIPTION("Common API for compressed memory storage");
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index bb62a4adc328..6a1827d3d231 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -240,7 +240,6 @@ struct mapping_area {
         enum zs_mapmode vm_mm; /* mapping mode */
 };
 
-
 /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
 static DEFINE_PER_CPU(struct mapping_area, zs_map_area);