drivers/xen/tmem.c - third_party/linux - Git at Google

 /*
  * Xen implementation for transcendent memory (tmem)
  *
  * Copyright (C) 2009-2011 Oracle Corp.  All rights reserved.
  * Author: Dan Magenheimer
  */

 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
 #include <linux/cleancache.h>
 #include <linux/frontswap.h>

 #include <xen/xen.h>
 #include <xen/interface/xen.h>
 #include <xen/page.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
 #include <xen/tmem.h>

 #ifndef CONFIG_XEN_TMEM_MODULE
 bool __read_mostly tmem_enabled = false;

 static int __init enable_tmem(char *s)
 {
 	tmem_enabled = true;
 	return 1;
 }
 __setup("tmem", enable_tmem);
 #endif

 #ifdef CONFIG_CLEANCACHE
 static bool cleancache __read_mostly = true;
 module_param(cleancache, bool, S_IRUGO);
 static bool selfballooning __read_mostly = true;
 module_param(selfballooning, bool, S_IRUGO);
 #endif /* CONFIG_CLEANCACHE */

 #ifdef CONFIG_FRONTSWAP
 static bool frontswap __read_mostly = true;
 module_param(frontswap, bool, S_IRUGO);
 #else /* CONFIG_FRONTSWAP */
 #define frontswap (0)
 #endif /* CONFIG_FRONTSWAP */

 #ifdef CONFIG_XEN_SELFBALLOONING
 static bool selfshrinking __read_mostly = true;
 module_param(selfshrinking, bool, S_IRUGO);
 #endif /* CONFIG_XEN_SELFBALLOONING */

 #define TMEM_CONTROL               0
 #define TMEM_NEW_POOL              1
 #define TMEM_DESTROY_POOL          2
 #define TMEM_NEW_PAGE              3
 #define TMEM_PUT_PAGE              4
 #define TMEM_GET_PAGE              5
 #define TMEM_FLUSH_PAGE            6
 #define TMEM_FLUSH_OBJECT          7
 #define TMEM_READ                  8
 #define TMEM_WRITE                 9
 #define TMEM_XCHG                 10

 /* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
 #define TMEM_POOL_PERSIST          1
 #define TMEM_POOL_SHARED           2
 #define TMEM_POOL_PAGESIZE_SHIFT   4
 #define TMEM_VERSION_SHIFT        24


 struct tmem_pool_uuid {
 	u64 uuid_lo;
 	u64 uuid_hi;
 };

 struct tmem_oid {
 	u64 oid[3];
 };

 #define TMEM_POOL_PRIVATE_UUID	{ 0, 0 }

 /* flags for tmem_ops.new_pool */
 #define TMEM_POOL_PERSIST          1
 #define TMEM_POOL_SHARED           2

 /* xen tmem foundation ops/hypercalls */

 static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
 	u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
 {
 	struct tmem_op op;
 	int rc = 0;

 	op.cmd = tmem_cmd;
 	op.pool_id = tmem_pool;
 	op.u.gen.oid[0] = oid.oid[0];
 	op.u.gen.oid[1] = oid.oid[1];
 	op.u.gen.oid[2] = oid.oid[2];
 	op.u.gen.index = index;
 	op.u.gen.tmem_offset = tmem_offset;
 	op.u.gen.pfn_offset = pfn_offset;
 	op.u.gen.len = len;
 	set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
 	rc = HYPERVISOR_tmem_op(&op);
 	return rc;
 }

 static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
 				u32 flags, unsigned long pagesize)
 {
 	struct tmem_op op;
 	int rc = 0, pageshift;

 	for (pageshift = 0; pagesize != 1; pageshift++)
 		pagesize >>= 1;
 	flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
 	flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
 	op.cmd = TMEM_NEW_POOL;
 	op.u.new.uuid[0] = uuid.uuid_lo;
 	op.u.new.uuid[1] = uuid.uuid_hi;
 	op.u.new.flags = flags;
 	rc = HYPERVISOR_tmem_op(&op);
 	return rc;
 }

 /* xen generic tmem ops */

 static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
 			     u32 index, struct page *page)
 {
 	return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
 			   xen_page_to_gfn(page), 0, 0, 0);
 }

 static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
 			     u32 index, struct page *page)
 {
 	return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
 			   xen_page_to_gfn(page), 0, 0, 0);
 }

 static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
 {
 	return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
 		0, 0, 0, 0);
 }

 static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
 {
 	return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
 }


 #ifdef CONFIG_CLEANCACHE
 static int xen_tmem_destroy_pool(u32 pool_id)
 {
 	struct tmem_oid oid = { { 0 } };

 	return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
 }

 /* cleancache ops */

 static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
 				     pgoff_t index, struct page *page)
 {
 	u32 ind = (u32) index;
 	struct tmem_oid oid = *(struct tmem_oid *)&key;

 	if (pool < 0)
 		return;
 	if (ind != index)
 		return;
 	mb(); /* ensure page is quiescent; tmem may address it with an alias */
 	(void)xen_tmem_put_page((u32)pool, oid, ind, page);
 }

 static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
 				    pgoff_t index, struct page *page)
 {
 	u32 ind = (u32) index;
 	struct tmem_oid oid = *(struct tmem_oid *)&key;
 	int ret;

 	/* translate return values to linux semantics */
 	if (pool < 0)
 		return -1;
 	if (ind != index)
 		return -1;
 	ret = xen_tmem_get_page((u32)pool, oid, ind, page);
 	if (ret == 1)
 		return 0;
 	else
 		return -1;
 }

 static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
 				       pgoff_t index)
 {
 	u32 ind = (u32) index;
 	struct tmem_oid oid = *(struct tmem_oid *)&key;

 	if (pool < 0)
 		return;
 	if (ind != index)
 		return;
 	(void)xen_tmem_flush_page((u32)pool, oid, ind);
 }

 static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
 {
 	struct tmem_oid oid = *(struct tmem_oid *)&key;

 	if (pool < 0)
 		return;
 	(void)xen_tmem_flush_object((u32)pool, oid);
 }

 static void tmem_cleancache_flush_fs(int pool)
 {
 	if (pool < 0)
 		return;
 	(void)xen_tmem_destroy_pool((u32)pool);
 }

 static int tmem_cleancache_init_fs(size_t pagesize)
 {
 	struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;

 	return xen_tmem_new_pool(uuid_private, 0, pagesize);
 }

 static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
 {
 	struct tmem_pool_uuid shared_uuid;

 	shared_uuid.uuid_lo = *(u64 *)uuid;
 	shared_uuid.uuid_hi = *(u64 *)(&uuid[8]);
 	return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
 }

 static const struct cleancache_ops tmem_cleancache_ops = {
 	.put_page = tmem_cleancache_put_page,
 	.get_page = tmem_cleancache_get_page,
 	.invalidate_page = tmem_cleancache_flush_page,
 	.invalidate_inode = tmem_cleancache_flush_inode,
 	.invalidate_fs = tmem_cleancache_flush_fs,
 	.init_shared_fs = tmem_cleancache_init_shared_fs,
 	.init_fs = tmem_cleancache_init_fs
 };
 #endif

 #ifdef CONFIG_FRONTSWAP
 /* frontswap tmem operations */

 /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
 static int tmem_frontswap_poolid;

 /*
  * Swizzling increases objects per swaptype, increasing tmem concurrency
  * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
  */
 #define SWIZ_BITS		4
 #define SWIZ_MASK		((1 << SWIZ_BITS) - 1)
 #define _oswiz(_type, _ind)	((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
 #define iswiz(_ind)		(_ind >> SWIZ_BITS)

 static inline struct tmem_oid oswiz(unsigned type, u32 ind)
 {
 	struct tmem_oid oid = { .oid = { 0 } };
 	oid.oid[0] = _oswiz(type, ind);
 	return oid;
 }

 /* returns 0 if the page was successfully put into frontswap, -1 if not */
 static int tmem_frontswap_store(unsigned type, pgoff_t offset,
 				   struct page *page)
 {
 	u64 ind64 = (u64)offset;
 	u32 ind = (u32)offset;
 	int pool = tmem_frontswap_poolid;
 	int ret;

 	if (pool < 0)
 		return -1;
 	if (ind64 != ind)
 		return -1;
 	mb(); /* ensure page is quiescent; tmem may address it with an alias */
 	ret = xen_tmem_put_page(pool, oswiz(type, ind), iswiz(ind), page);
 	/* translate Xen tmem return values to linux semantics */
 	if (ret == 1)
 		return 0;
 	else
 		return -1;
 }

 /*
  * returns 0 if the page was successfully gotten from frontswap, -1 if
  * was not present (should never happen!)
  */
 static int tmem_frontswap_load(unsigned type, pgoff_t offset,
 				   struct page *page)
 {
 	u64 ind64 = (u64)offset;
 	u32 ind = (u32)offset;
 	int pool = tmem_frontswap_poolid;
 	int ret;

 	if (pool < 0)
 		return -1;
 	if (ind64 != ind)
 		return -1;
 	ret = xen_tmem_get_page(pool, oswiz(type, ind), iswiz(ind), page);
 	/* translate Xen tmem return values to linux semantics */
 	if (ret == 1)
 		return 0;
 	else
 		return -1;
 }

 /* flush a single page from frontswap */
 static void tmem_frontswap_flush_page(unsigned type, pgoff_t offset)
 {
 	u64 ind64 = (u64)offset;
 	u32 ind = (u32)offset;
 	int pool = tmem_frontswap_poolid;

 	if (pool < 0)
 		return;
 	if (ind64 != ind)
 		return;
 	(void) xen_tmem_flush_page(pool, oswiz(type, ind), iswiz(ind));
 }

 /* flush all pages from the passed swaptype */
 static void tmem_frontswap_flush_area(unsigned type)
 {
 	int pool = tmem_frontswap_poolid;
 	int ind;

 	if (pool < 0)
 		return;
 	for (ind = SWIZ_MASK; ind >= 0; ind--)
 		(void)xen_tmem_flush_object(pool, oswiz(type, ind));
 }

 static void tmem_frontswap_init(unsigned ignored)
 {
 	struct tmem_pool_uuid private = TMEM_POOL_PRIVATE_UUID;

 	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
 	if (tmem_frontswap_poolid < 0)
 		tmem_frontswap_poolid =
 		    xen_tmem_new_pool(private, TMEM_POOL_PERSIST, PAGE_SIZE);
 }

 static struct frontswap_ops tmem_frontswap_ops = {
 	.store = tmem_frontswap_store,
 	.load = tmem_frontswap_load,
 	.invalidate_page = tmem_frontswap_flush_page,
 	.invalidate_area = tmem_frontswap_flush_area,
 	.init = tmem_frontswap_init
 };
 #endif

 static int __init xen_tmem_init(void)
 {
 	if (!xen_domain())
 		return 0;
 #ifdef CONFIG_FRONTSWAP
 	if (tmem_enabled && frontswap) {
 		char *s = "";

 		tmem_frontswap_poolid = -1;
 		frontswap_register_ops(&tmem_frontswap_ops);
 		pr_info("frontswap enabled, RAM provided by Xen Transcendent Memory%s\n",
 			s);
 	}
 #endif
 #ifdef CONFIG_CLEANCACHE
 	BUILD_BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
 	if (tmem_enabled && cleancache) {
 		int err;

 		err = cleancache_register_ops(&tmem_cleancache_ops);
 		if (err)
 			pr_warn("xen-tmem: failed to enable cleancache: %d\n",
 				err);
 		else
 			pr_info("cleancache enabled, RAM provided by "
 				"Xen Transcendent Memory\n");
 	}
 #endif
 #ifdef CONFIG_XEN_SELFBALLOONING
 	/*
 	 * There is no point of driving pages to the swap system if they
 	 * aren't going anywhere in tmem universe.
 	 */
 	if (!frontswap) {
 		selfshrinking = false;
 		selfballooning = false;
 	}
 	xen_selfballoon_init(selfballooning, selfshrinking);
 #endif
 	return 0;
 }

 module_init(xen_tmem_init)
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
 MODULE_DESCRIPTION("Shim to Xen transcendent memory");
	/*
	* Xen implementation for transcendent memory (tmem)
	*
	* Copyright (C) 2009-2011 Oracle Corp. All rights reserved.
	* Author: Dan Magenheimer
	*/

	#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/types.h>
	#include <linux/init.h>
	#include <linux/pagemap.h>
	#include <linux/cleancache.h>
	#include <linux/frontswap.h>

	#include <xen/xen.h>
	#include <xen/interface/xen.h>
	#include <xen/page.h>
	#include <asm/xen/hypercall.h>
	#include <asm/xen/hypervisor.h>
	#include <xen/tmem.h>

	#ifndef CONFIG_XEN_TMEM_MODULE
	bool __read_mostly tmem_enabled = false;

	static int __init enable_tmem(char *s)
	{
	tmem_enabled = true;
	return 1;
	}
	__setup("tmem", enable_tmem);
	#endif

	#ifdef CONFIG_CLEANCACHE
	static bool cleancache __read_mostly = true;
	module_param(cleancache, bool, S_IRUGO);
	static bool selfballooning __read_mostly = true;
	module_param(selfballooning, bool, S_IRUGO);
	#endif /* CONFIG_CLEANCACHE */

	#ifdef CONFIG_FRONTSWAP
	static bool frontswap __read_mostly = true;
	module_param(frontswap, bool, S_IRUGO);
	#else /* CONFIG_FRONTSWAP */
	#define frontswap (0)
	#endif /* CONFIG_FRONTSWAP */

	#ifdef CONFIG_XEN_SELFBALLOONING
	static bool selfshrinking __read_mostly = true;
	module_param(selfshrinking, bool, S_IRUGO);
	#endif /* CONFIG_XEN_SELFBALLOONING */

	#define TMEM_CONTROL 0
	#define TMEM_NEW_POOL 1
	#define TMEM_DESTROY_POOL 2
	#define TMEM_NEW_PAGE 3
	#define TMEM_PUT_PAGE 4
	#define TMEM_GET_PAGE 5
	#define TMEM_FLUSH_PAGE 6
	#define TMEM_FLUSH_OBJECT 7
	#define TMEM_READ 8
	#define TMEM_WRITE 9
	#define TMEM_XCHG 10

	/* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
	#define TMEM_POOL_PERSIST 1
	#define TMEM_POOL_SHARED 2
	#define TMEM_POOL_PAGESIZE_SHIFT 4
	#define TMEM_VERSION_SHIFT 24


	struct tmem_pool_uuid {
	u64 uuid_lo;
	u64 uuid_hi;
	};

	struct tmem_oid {
	u64 oid[3];
	};

	#define TMEM_POOL_PRIVATE_UUID { 0, 0 }

	/* flags for tmem_ops.new_pool */
	#define TMEM_POOL_PERSIST 1
	#define TMEM_POOL_SHARED 2

	/* xen tmem foundation ops/hypercalls */

	static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
	u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
	{
	struct tmem_op op;
	int rc = 0;

	op.cmd = tmem_cmd;
	op.pool_id = tmem_pool;
	op.u.gen.oid[0] = oid.oid[0];
	op.u.gen.oid[1] = oid.oid[1];
	op.u.gen.oid[2] = oid.oid[2];
	op.u.gen.index = index;
	op.u.gen.tmem_offset = tmem_offset;
	op.u.gen.pfn_offset = pfn_offset;
	op.u.gen.len = len;
	set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
	rc = HYPERVISOR_tmem_op(&op);
	return rc;
	}

	static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
	u32 flags, unsigned long pagesize)
	{
	struct tmem_op op;
	int rc = 0, pageshift;

	for (pageshift = 0; pagesize != 1; pageshift++)
	pagesize >>= 1;
	flags \|= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
	flags \|= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
	op.cmd = TMEM_NEW_POOL;
	op.u.new.uuid[0] = uuid.uuid_lo;
	op.u.new.uuid[1] = uuid.uuid_hi;
	op.u.new.flags = flags;
	rc = HYPERVISOR_tmem_op(&op);
	return rc;
	}

	/* xen generic tmem ops */

	static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
	u32 index, struct page *page)
	{
	return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
	xen_page_to_gfn(page), 0, 0, 0);
	}

	static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
	u32 index, struct page *page)
	{
	return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
	xen_page_to_gfn(page), 0, 0, 0);
	}

	static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
	{
	return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
	0, 0, 0, 0);
	}

	static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
	{
	return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
	}


	#ifdef CONFIG_CLEANCACHE
	static int xen_tmem_destroy_pool(u32 pool_id)
	{
	struct tmem_oid oid = { { 0 } };

	return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
	}

	/* cleancache ops */

	static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
	pgoff_t index, struct page *page)
	{
	u32 ind = (u32) index;
	struct tmem_oid oid = (struct tmem_oid )&key;

	if (pool < 0)
	return;
	if (ind != index)
	return;
	mb(); /* ensure page is quiescent; tmem may address it with an alias */
	(void)xen_tmem_put_page((u32)pool, oid, ind, page);
	}

	static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
	pgoff_t index, struct page *page)
	{
	u32 ind = (u32) index;
	struct tmem_oid oid = (struct tmem_oid )&key;
	int ret;

	/* translate return values to linux semantics */
	if (pool < 0)
	return -1;
	if (ind != index)
	return -1;
	ret = xen_tmem_get_page((u32)pool, oid, ind, page);
	if (ret == 1)
	return 0;
	else
	return -1;
	}

	static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
	pgoff_t index)
	{
	u32 ind = (u32) index;
	struct tmem_oid oid = (struct tmem_oid )&key;

	if (pool < 0)
	return;
	if (ind != index)
	return;
	(void)xen_tmem_flush_page((u32)pool, oid, ind);
	}

	static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
	{
	struct tmem_oid oid = (struct tmem_oid )&key;

	if (pool < 0)
	return;
	(void)xen_tmem_flush_object((u32)pool, oid);
	}

	static void tmem_cleancache_flush_fs(int pool)
	{
	if (pool < 0)
	return;
	(void)xen_tmem_destroy_pool((u32)pool);
	}

	static int tmem_cleancache_init_fs(size_t pagesize)
	{
	struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;

	return xen_tmem_new_pool(uuid_private, 0, pagesize);
	}

	static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
	{
	struct tmem_pool_uuid shared_uuid;

	shared_uuid.uuid_lo = (u64 )uuid;
	shared_uuid.uuid_hi = (u64 )(&uuid[8]);
	return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
	}

	static const struct cleancache_ops tmem_cleancache_ops = {
	.put_page = tmem_cleancache_put_page,
	.get_page = tmem_cleancache_get_page,
	.invalidate_page = tmem_cleancache_flush_page,
	.invalidate_inode = tmem_cleancache_flush_inode,
	.invalidate_fs = tmem_cleancache_flush_fs,
	.init_shared_fs = tmem_cleancache_init_shared_fs,
	.init_fs = tmem_cleancache_init_fs
	};
	#endif

	#ifdef CONFIG_FRONTSWAP
	/* frontswap tmem operations */

	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
	static int tmem_frontswap_poolid;

	/*
	* Swizzling increases objects per swaptype, increasing tmem concurrency
	* for heavy swaploads. Later, larger nr_cpus -> larger SWIZ_BITS
	*/
	#define SWIZ_BITS 4
	#define SWIZ_MASK ((1 << SWIZ_BITS) - 1)
	#define _oswiz(_type, _ind) ((_type << SWIZ_BITS) \| (_ind & SWIZ_MASK))
	#define iswiz(_ind) (_ind >> SWIZ_BITS)

	static inline struct tmem_oid oswiz(unsigned type, u32 ind)
	{
	struct tmem_oid oid = { .oid = { 0 } };
	oid.oid[0] = _oswiz(type, ind);
	return oid;
	}

	/* returns 0 if the page was successfully put into frontswap, -1 if not */
	static int tmem_frontswap_store(unsigned type, pgoff_t offset,
	struct page *page)
	{
	u64 ind64 = (u64)offset;
	u32 ind = (u32)offset;
	int pool = tmem_frontswap_poolid;
	int ret;

	if (pool < 0)
	return -1;
	if (ind64 != ind)
	return -1;
	mb(); /* ensure page is quiescent; tmem may address it with an alias */
	ret = xen_tmem_put_page(pool, oswiz(type, ind), iswiz(ind), page);
	/* translate Xen tmem return values to linux semantics */
	if (ret == 1)
	return 0;
	else
	return -1;
	}

	/*
	* returns 0 if the page was successfully gotten from frontswap, -1 if
	* was not present (should never happen!)
	*/
	static int tmem_frontswap_load(unsigned type, pgoff_t offset,
	struct page *page)
	{
	u64 ind64 = (u64)offset;
	u32 ind = (u32)offset;
	int pool = tmem_frontswap_poolid;
	int ret;

	if (pool < 0)
	return -1;
	if (ind64 != ind)
	return -1;
	ret = xen_tmem_get_page(pool, oswiz(type, ind), iswiz(ind), page);
	/* translate Xen tmem return values to linux semantics */
	if (ret == 1)
	return 0;
	else
	return -1;
	}

	/* flush a single page from frontswap */
	static void tmem_frontswap_flush_page(unsigned type, pgoff_t offset)
	{
	u64 ind64 = (u64)offset;
	u32 ind = (u32)offset;
	int pool = tmem_frontswap_poolid;

	if (pool < 0)
	return;
	if (ind64 != ind)
	return;
	(void) xen_tmem_flush_page(pool, oswiz(type, ind), iswiz(ind));
	}

	/* flush all pages from the passed swaptype */
	static void tmem_frontswap_flush_area(unsigned type)
	{
	int pool = tmem_frontswap_poolid;
	int ind;

	if (pool < 0)
	return;
	for (ind = SWIZ_MASK; ind >= 0; ind--)
	(void)xen_tmem_flush_object(pool, oswiz(type, ind));
	}

	static void tmem_frontswap_init(unsigned ignored)
	{
	struct tmem_pool_uuid private = TMEM_POOL_PRIVATE_UUID;

	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
	if (tmem_frontswap_poolid < 0)
	tmem_frontswap_poolid =
	xen_tmem_new_pool(private, TMEM_POOL_PERSIST, PAGE_SIZE);
	}

	static struct frontswap_ops tmem_frontswap_ops = {
	.store = tmem_frontswap_store,
	.load = tmem_frontswap_load,
	.invalidate_page = tmem_frontswap_flush_page,
	.invalidate_area = tmem_frontswap_flush_area,
	.init = tmem_frontswap_init
	};
	#endif

	static int __init xen_tmem_init(void)
	{
	if (!xen_domain())
	return 0;
	#ifdef CONFIG_FRONTSWAP
	if (tmem_enabled && frontswap) {
	char *s = "";

	tmem_frontswap_poolid = -1;
	frontswap_register_ops(&tmem_frontswap_ops);
	pr_info("frontswap enabled, RAM provided by Xen Transcendent Memory%s\n",
	s);
	}
	#endif
	#ifdef CONFIG_CLEANCACHE
	BUILD_BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
	if (tmem_enabled && cleancache) {
	int err;

	err = cleancache_register_ops(&tmem_cleancache_ops);
	if (err)
	pr_warn("xen-tmem: failed to enable cleancache: %d\n",
	err);
	else
	pr_info("cleancache enabled, RAM provided by "
	"Xen Transcendent Memory\n");
	}
	#endif
	#ifdef CONFIG_XEN_SELFBALLOONING
	/*
	* There is no point of driving pages to the swap system if they
	* aren't going anywhere in tmem universe.
	*/
	if (!frontswap) {
	selfshrinking = false;
	selfballooning = false;
	}
	xen_selfballoon_init(selfballooning, selfshrinking);
	#endif
	return 0;
	}

	module_init(xen_tmem_init)
	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
	MODULE_DESCRIPTION("Shim to Xen transcendent memory");