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

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

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

 /* temporary ifdef until include/linux/frontswap.h is upstream */
 #ifdef CONFIG_FRONTSWAP
 #include <linux/frontswap.h>
 #endif

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

 #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, unsigned long pfn)
 {
 	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;

 	return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
 		gmfn, 0, 0, 0);
 }

 static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
 			     u32 index, unsigned long pfn)
 {
 	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;

 	return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
 		gmfn, 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);
 }

 bool __read_mostly tmem_enabled = false;

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

 #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;
 	unsigned long pfn = page_to_pfn(page);

 	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, pfn);
 }

 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;
 	unsigned long pfn = page_to_pfn(page);
 	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, pfn);
 	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 bool __initdata use_cleancache = true;

 static int __init no_cleancache(char *s)
 {
 	use_cleancache = false;
 	return 1;
 }
 __setup("nocleancache", no_cleancache);

 static struct cleancache_ops __initdata 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;
 	unsigned long pfn = page_to_pfn(page);
 	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), pfn);
 	/* 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;
 	unsigned long pfn = page_to_pfn(page);
 	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), pfn);
 	/* 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 bool __initdata use_frontswap = true;

 static int __init no_frontswap(char *s)
 {
 	use_frontswap = false;
 	return 1;
 }
 __setup("nofrontswap", no_frontswap);

 static struct frontswap_ops __initdata 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 && use_frontswap) {
 		char *s = "";
 		struct frontswap_ops old_ops =
 			frontswap_register_ops(&tmem_frontswap_ops);

 		tmem_frontswap_poolid = -1;
 		if (old_ops.init != NULL)
 			s = " (WARNING: frontswap_ops overridden)";
 		printk(KERN_INFO "frontswap enabled, RAM provided by "
 				 "Xen Transcendent Memory\n");
 	}
 #endif
 #ifdef CONFIG_CLEANCACHE
 	BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
 	if (tmem_enabled && use_cleancache) {
 		char *s = "";
 		struct cleancache_ops old_ops =
 			cleancache_register_ops(&tmem_cleancache_ops);
 		if (old_ops.init_fs != NULL)
 			s = " (WARNING: cleancache_ops overridden)";
 		printk(KERN_INFO "cleancache enabled, RAM provided by "
 				 "Xen Transcendent Memory%s\n", s);
 	}
 #endif
 	return 0;
 }

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

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

	/* temporary ifdef until include/linux/frontswap.h is upstream */
	#ifdef CONFIG_FRONTSWAP
	#include <linux/frontswap.h>
	#endif

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

	#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, unsigned long pfn)
	{
	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;

	return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
	gmfn, 0, 0, 0);
	}

	static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
	u32 index, unsigned long pfn)
	{
	unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;

	return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
	gmfn, 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);
	}

	bool __read_mostly tmem_enabled = false;

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

	#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;
	unsigned long pfn = page_to_pfn(page);

	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, pfn);
	}

	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;
	unsigned long pfn = page_to_pfn(page);
	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, pfn);
	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 bool __initdata use_cleancache = true;

	static int __init no_cleancache(char *s)
	{
	use_cleancache = false;
	return 1;
	}
	__setup("nocleancache", no_cleancache);

	static struct cleancache_ops __initdata 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;
	unsigned long pfn = page_to_pfn(page);
	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), pfn);
	/* 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;
	unsigned long pfn = page_to_pfn(page);
	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), pfn);
	/* 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 bool __initdata use_frontswap = true;

	static int __init no_frontswap(char *s)
	{
	use_frontswap = false;
	return 1;
	}
	__setup("nofrontswap", no_frontswap);

	static struct frontswap_ops __initdata 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 && use_frontswap) {
	char *s = "";
	struct frontswap_ops old_ops =
	frontswap_register_ops(&tmem_frontswap_ops);

	tmem_frontswap_poolid = -1;
	if (old_ops.init != NULL)
	s = " (WARNING: frontswap_ops overridden)";
	printk(KERN_INFO "frontswap enabled, RAM provided by "
	"Xen Transcendent Memory\n");
	}
	#endif
	#ifdef CONFIG_CLEANCACHE
	BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
	if (tmem_enabled && use_cleancache) {
	char *s = "";
	struct cleancache_ops old_ops =
	cleancache_register_ops(&tmem_cleancache_ops);
	if (old_ops.init_fs != NULL)
	s = " (WARNING: cleancache_ops overridden)";
	printk(KERN_INFO "cleancache enabled, RAM provided by "
	"Xen Transcendent Memory%s\n", s);
	}
	#endif
	return 0;
	}

	module_init(xen_tmem_init)