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 <[email protected]>
Tested-by: Seth Jennings <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: Weijie Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/zpool.h

@@ -0,0 +1,106 @@
+/*
+ * zpool memory storage api
+ *
+ * Copyright (C) 2014 Dan Streetman
+ *
+ * This is a common frontend for the zbud and zsmalloc memory
+ * storage pool implementations.  Typically, this is used to
+ * store compressed memory.
+ */
+
+#ifndef _ZPOOL_H_
+#define _ZPOOL_H_
+
+struct zpool;
+
+struct zpool_ops {
+	int (*evict)(struct zpool *pool, unsigned long handle);
+};
+
+/*
+ * Control how a handle is mapped.  It will be ignored if the
+ * implementation does not support it.  Its use is optional.
+ * Note that this does not refer to memory protection, it
+ * refers to how the memory will be copied in/out if copying
+ * is necessary during mapping; read-write is the safest as
+ * it copies the existing memory in on map, and copies the
+ * changed memory back out on unmap.  Write-only does not copy
+ * in the memory and should only be used for initialization.
+ * If in doubt, use ZPOOL_MM_DEFAULT which is read-write.
+ */
+enum zpool_mapmode {
+	ZPOOL_MM_RW, /* normal read-write mapping */
+	ZPOOL_MM_RO, /* read-only (no copy-out at unmap time) */
+	ZPOOL_MM_WO, /* write-only (no copy-in at map time) */
+
+	ZPOOL_MM_DEFAULT = ZPOOL_MM_RW
+};
+
+struct zpool *zpool_create_pool(char *type, gfp_t gfp, struct zpool_ops *ops);
+
+char *zpool_get_type(struct zpool *pool);
+
+void zpool_destroy_pool(struct zpool *pool);
+
+int zpool_malloc(struct zpool *pool, size_t size, gfp_t gfp,
+			unsigned long *handle);
+
+void zpool_free(struct zpool *pool, unsigned long handle);
+
+int zpool_shrink(struct zpool *pool, unsigned int pages,
+			unsigned int *reclaimed);
+
+void *zpool_map_handle(struct zpool *pool, unsigned long handle,
+			enum zpool_mapmode mm);
+
+void zpool_unmap_handle(struct zpool *pool, unsigned long handle);
+
+u64 zpool_get_total_size(struct zpool *pool);
+
+
+/**
+ * struct zpool_driver - driver implementation for zpool
+ * @type:	name of the driver.
+ * @list:	entry in the list of zpool drivers.
+ * @create:	create a new pool.
+ * @destroy:	destroy a pool.
+ * @malloc:	allocate mem from a pool.
+ * @free:	free mem from a pool.
+ * @shrink:	shrink the pool.
+ * @map:	map a handle.
+ * @unmap:	unmap a handle.
+ * @total_size:	get total size of a pool.
+ *
+ * This is created by a zpool implementation and registered
+ * with zpool.
+ */
+struct zpool_driver {
+	char *type;
+	struct module *owner;
+	atomic_t refcount;
+	struct list_head list;
+
+	void *(*create)(gfp_t gfp, struct zpool_ops *ops);
+	void (*destroy)(void *pool);
+
+	int (*malloc)(void *pool, size_t size, gfp_t gfp,
+				unsigned long *handle);
+	void (*free)(void *pool, unsigned long handle);
+
+	int (*shrink)(void *pool, unsigned int pages,
+				unsigned int *reclaimed);
+
+	void *(*map)(void *pool, unsigned long handle,
+				enum zpool_mapmode mm);
+	void (*unmap)(void *pool, unsigned long handle);
+
+	u64 (*total_size)(void *pool);
+};
+
+void zpool_register_driver(struct zpool_driver *driver);
+
+int zpool_unregister_driver(struct zpool_driver *driver);
+
+int zpool_evict(void *pool, unsigned long handle);
+
+#endif

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"

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