mm/page_cgroup.c - linux - Git at Google

 #include <linux/mm.h>
 #include <linux/mmzone.h>
 #include <linux/bootmem.h>
 #include <linux/bit_spinlock.h>
 #include <linux/page_cgroup.h>
 #include <linux/hash.h>
 #include <linux/slab.h>
 #include <linux/memory.h>
 #include <linux/vmalloc.h>
 #include <linux/cgroup.h>
 #include <linux/swapops.h>

 static void __meminit
 __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
 {
 	pc->flags = 0;
 	pc->mem_cgroup = NULL;
 	pc->page = pfn_to_page(pfn);
 }
 static unsigned long total_usage;

 #if !defined(CONFIG_SPARSEMEM)


 void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
 {
 	pgdat->node_page_cgroup = NULL;
 }

 struct page_cgroup *lookup_page_cgroup(struct page *page)
 {
 	unsigned long pfn = page_to_pfn(page);
 	unsigned long offset;
 	struct page_cgroup *base;

 	base = NODE_DATA(page_to_nid(page))->node_page_cgroup;
 	if (unlikely(!base))
 		return NULL;

 	offset = pfn - NODE_DATA(page_to_nid(page))->node_start_pfn;
 	return base + offset;
 }

 static int __init alloc_node_page_cgroup(int nid)
 {
 	struct page_cgroup *base, *pc;
 	unsigned long table_size;
 	unsigned long start_pfn, nr_pages, index;

 	start_pfn = NODE_DATA(nid)->node_start_pfn;
 	nr_pages = NODE_DATA(nid)->node_spanned_pages;

 	if (!nr_pages)
 		return 0;

 	table_size = sizeof(struct page_cgroup) * nr_pages;

 	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
 			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
 	if (!base)
 		return -ENOMEM;
 	for (index = 0; index < nr_pages; index++) {
 		pc = base + index;
 		__init_page_cgroup(pc, start_pfn + index);
 	}
 	NODE_DATA(nid)->node_page_cgroup = base;
 	total_usage += table_size;
 	return 0;
 }

 void __init page_cgroup_init(void)
 {

 	int nid, fail;

 	if (mem_cgroup_subsys.disabled)
 		return;

 	for_each_online_node(nid)  {
 		fail = alloc_node_page_cgroup(nid);
 		if (fail)
 			goto fail;
 	}
 	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
 	printk(KERN_INFO "please try cgroup_disable=memory option if you"
 	" don't want\n");
 	return;
 fail:
 	printk(KERN_CRIT "allocation of page_cgroup was failed.\n");
 	printk(KERN_CRIT "please try cgroup_disable=memory boot option\n");
 	panic("Out of memory");
 }

 #else /* CONFIG_FLAT_NODE_MEM_MAP */

 struct page_cgroup *lookup_page_cgroup(struct page *page)
 {
 	unsigned long pfn = page_to_pfn(page);
 	struct mem_section *section = __pfn_to_section(pfn);

 	return section->page_cgroup + pfn;
 }

 /* __alloc_bootmem...() is protected by !slab_available() */
 static int __init_refok init_section_page_cgroup(unsigned long pfn)
 {
 	struct mem_section *section = __pfn_to_section(pfn);
 	struct page_cgroup *base, *pc;
 	unsigned long table_size;
 	int nid, index;

 	if (!section->page_cgroup) {
 		nid = page_to_nid(pfn_to_page(pfn));
 		table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
 		if (slab_is_available()) {
 			base = kmalloc_node(table_size, GFP_KERNEL, nid);
 			if (!base)
 				base = vmalloc_node(table_size, nid);
 		} else {
 			base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
 				table_size,
 				PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
 		}
 	} else {
 		/*
  		 * We don't have to allocate page_cgroup again, but
 		 * address of memmap may be changed. So, we have to initialize
 		 * again.
 		 */
 		base = section->page_cgroup + pfn;
 		table_size = 0;
 		/* check address of memmap is changed or not. */
 		if (base->page == pfn_to_page(pfn))
 			return 0;
 	}

 	if (!base) {
 		printk(KERN_ERR "page cgroup allocation failure\n");
 		return -ENOMEM;
 	}

 	for (index = 0; index < PAGES_PER_SECTION; index++) {
 		pc = base + index;
 		__init_page_cgroup(pc, pfn + index);
 	}

 	section->page_cgroup = base - pfn;
 	total_usage += table_size;
 	return 0;
 }
 #ifdef CONFIG_MEMORY_HOTPLUG
 void __free_page_cgroup(unsigned long pfn)
 {
 	struct mem_section *ms;
 	struct page_cgroup *base;

 	ms = __pfn_to_section(pfn);
 	if (!ms || !ms->page_cgroup)
 		return;
 	base = ms->page_cgroup + pfn;
 	if (is_vmalloc_addr(base)) {
 		vfree(base);
 		ms->page_cgroup = NULL;
 	} else {
 		struct page *page = virt_to_page(base);
 		if (!PageReserved(page)) { /* Is bootmem ? */
 			kfree(base);
 			ms->page_cgroup = NULL;
 		}
 	}
 }

 int __meminit online_page_cgroup(unsigned long start_pfn,
 			unsigned long nr_pages,
 			int nid)
 {
 	unsigned long start, end, pfn;
 	int fail = 0;

 	start = start_pfn & ~(PAGES_PER_SECTION - 1);
 	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);

 	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
 		if (!pfn_present(pfn))
 			continue;
 		fail = init_section_page_cgroup(pfn);
 	}
 	if (!fail)
 		return 0;

 	/* rollback */
 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 		__free_page_cgroup(pfn);

 	return -ENOMEM;
 }

 int __meminit offline_page_cgroup(unsigned long start_pfn,
 		unsigned long nr_pages, int nid)
 {
 	unsigned long start, end, pfn;

 	start = start_pfn & ~(PAGES_PER_SECTION - 1);
 	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);

 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 		__free_page_cgroup(pfn);
 	return 0;

 }

 static int __meminit page_cgroup_callback(struct notifier_block *self,
 			       unsigned long action, void *arg)
 {
 	struct memory_notify *mn = arg;
 	int ret = 0;
 	switch (action) {
 	case MEM_GOING_ONLINE:
 		ret = online_page_cgroup(mn->start_pfn,
 				   mn->nr_pages, mn->status_change_nid);
 		break;
 	case MEM_OFFLINE:
 		offline_page_cgroup(mn->start_pfn,
 				mn->nr_pages, mn->status_change_nid);
 		break;
 	case MEM_CANCEL_ONLINE:
 	case MEM_GOING_OFFLINE:
 		break;
 	case MEM_ONLINE:
 	case MEM_CANCEL_OFFLINE:
 		break;
 	}

 	if (ret)
 		ret = notifier_from_errno(ret);
 	else
 		ret = NOTIFY_OK;

 	return ret;
 }

 #endif

 void __init page_cgroup_init(void)
 {
 	unsigned long pfn;
 	int fail = 0;

 	if (mem_cgroup_subsys.disabled)
 		return;

 	for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
 		if (!pfn_present(pfn))
 			continue;
 		fail = init_section_page_cgroup(pfn);
 	}
 	if (fail) {
 		printk(KERN_CRIT "try cgroup_disable=memory boot option\n");
 		panic("Out of memory");
 	} else {
 		hotplug_memory_notifier(page_cgroup_callback, 0);
 	}
 	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
 	printk(KERN_INFO "please try cgroup_disable=memory option if you don't"
 	" want\n");
 }

 void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
 {
 	return;
 }

 #endif


 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP

 static DEFINE_MUTEX(swap_cgroup_mutex);
 struct swap_cgroup_ctrl {
 	struct page **map;
 	unsigned long length;
 };

 struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];

 /*
  * This 8bytes seems big..maybe we can reduce this when we can use "id" for
  * cgroup rather than pointer.
  */
 struct swap_cgroup {
 	struct mem_cgroup	*val;
 };
 #define SC_PER_PAGE	(PAGE_SIZE/sizeof(struct swap_cgroup))
 #define SC_POS_MASK	(SC_PER_PAGE - 1)

 /*
  * SwapCgroup implements "lookup" and "exchange" operations.
  * In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
  * against SwapCache. At swap_free(), this is accessed directly from swap.
  *
  * This means,
  *  - we have no race in "exchange" when we're accessed via SwapCache because
  *    SwapCache(and its swp_entry) is under lock.
  *  - When called via swap_free(), there is no user of this entry and no race.
  * Then, we don't need lock around "exchange".
  *
  * TODO: we can push these buffers out to HIGHMEM.
  */

 /*
  * allocate buffer for swap_cgroup.
  */
 static int swap_cgroup_prepare(int type)
 {
 	struct page *page;
 	struct swap_cgroup_ctrl *ctrl;
 	unsigned long idx, max;

 	if (!do_swap_account)
 		return 0;
 	ctrl = &swap_cgroup_ctrl[type];

 	for (idx = 0; idx < ctrl->length; idx++) {
 		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (!page)
 			goto not_enough_page;
 		ctrl->map[idx] = page;
 	}
 	return 0;
 not_enough_page:
 	max = idx;
 	for (idx = 0; idx < max; idx++)
 		__free_page(ctrl->map[idx]);

 	return -ENOMEM;
 }

 /**
  * swap_cgroup_record - record mem_cgroup for this swp_entry.
  * @ent: swap entry to be recorded into
  * @mem: mem_cgroup to be recorded
  *
  * Returns old value at success, NULL at failure.
  * (Of course, old value can be NULL.)
  */
 struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem)
 {
 	int type = swp_type(ent);
 	unsigned long offset = swp_offset(ent);
 	unsigned long idx = offset / SC_PER_PAGE;
 	unsigned long pos = offset & SC_POS_MASK;
 	struct swap_cgroup_ctrl *ctrl;
 	struct page *mappage;
 	struct swap_cgroup *sc;
 	struct mem_cgroup *old;

 	if (!do_swap_account)
 		return NULL;

 	ctrl = &swap_cgroup_ctrl[type];

 	mappage = ctrl->map[idx];
 	sc = page_address(mappage);
 	sc += pos;
 	old = sc->val;
 	sc->val = mem;

 	return old;
 }

 /**
  * lookup_swap_cgroup - lookup mem_cgroup tied to swap entry
  * @ent: swap entry to be looked up.
  *
  * Returns pointer to mem_cgroup at success. NULL at failure.
  */
 struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
 {
 	int type = swp_type(ent);
 	unsigned long offset = swp_offset(ent);
 	unsigned long idx = offset / SC_PER_PAGE;
 	unsigned long pos = offset & SC_POS_MASK;
 	struct swap_cgroup_ctrl *ctrl;
 	struct page *mappage;
 	struct swap_cgroup *sc;
 	struct mem_cgroup *ret;

 	if (!do_swap_account)
 		return NULL;

 	ctrl = &swap_cgroup_ctrl[type];
 	mappage = ctrl->map[idx];
 	sc = page_address(mappage);
 	sc += pos;
 	ret = sc->val;
 	return ret;
 }

 int swap_cgroup_swapon(int type, unsigned long max_pages)
 {
 	void *array;
 	unsigned long array_size;
 	unsigned long length;
 	struct swap_cgroup_ctrl *ctrl;

 	if (!do_swap_account)
 		return 0;

 	length = ((max_pages/SC_PER_PAGE) + 1);
 	array_size = length * sizeof(void *);

 	array = vmalloc(array_size);
 	if (!array)
 		goto nomem;

 	memset(array, 0, array_size);
 	ctrl = &swap_cgroup_ctrl[type];
 	mutex_lock(&swap_cgroup_mutex);
 	ctrl->length = length;
 	ctrl->map = array;
 	if (swap_cgroup_prepare(type)) {
 		/* memory shortage */
 		ctrl->map = NULL;
 		ctrl->length = 0;
 		vfree(array);
 		mutex_unlock(&swap_cgroup_mutex);
 		goto nomem;
 	}
 	mutex_unlock(&swap_cgroup_mutex);

 	printk(KERN_INFO
 		"swap_cgroup: uses %ld bytes of vmalloc for pointer array space"
 		" and %ld bytes to hold mem_cgroup pointers on swap\n",
 		array_size, length * PAGE_SIZE);
 	printk(KERN_INFO
 	"swap_cgroup can be disabled by noswapaccount boot option.\n");

 	return 0;
 nomem:
 	printk(KERN_INFO "couldn't allocate enough memory for swap_cgroup.\n");
 	printk(KERN_INFO
 		"swap_cgroup can be disabled by noswapaccount boot option\n");
 	return -ENOMEM;
 }

 void swap_cgroup_swapoff(int type)
 {
 	int i;
 	struct swap_cgroup_ctrl *ctrl;

 	if (!do_swap_account)
 		return;

 	mutex_lock(&swap_cgroup_mutex);
 	ctrl = &swap_cgroup_ctrl[type];
 	if (ctrl->map) {
 		for (i = 0; i < ctrl->length; i++) {
 			struct page *page = ctrl->map[i];
 			if (page)
 				__free_page(page);
 		}
 		vfree(ctrl->map);
 		ctrl->map = NULL;
 		ctrl->length = 0;
 	}
 	mutex_unlock(&swap_cgroup_mutex);
 }

 #endif
	#include <linux/mm.h>
	#include <linux/mmzone.h>
	#include <linux/bootmem.h>
	#include <linux/bit_spinlock.h>
	#include <linux/page_cgroup.h>
	#include <linux/hash.h>
	#include <linux/slab.h>
	#include <linux/memory.h>
	#include <linux/vmalloc.h>
	#include <linux/cgroup.h>
	#include <linux/swapops.h>

	static void __meminit
	__init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
	{
	pc->flags = 0;
	pc->mem_cgroup = NULL;
	pc->page = pfn_to_page(pfn);
	}
	static unsigned long total_usage;

	#if !defined(CONFIG_SPARSEMEM)


	void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
	{
	pgdat->node_page_cgroup = NULL;
	}

	struct page_cgroup lookup_page_cgroup(struct page page)
	{
	unsigned long pfn = page_to_pfn(page);
	unsigned long offset;
	struct page_cgroup *base;

	base = NODE_DATA(page_to_nid(page))->node_page_cgroup;
	if (unlikely(!base))
	return NULL;

	offset = pfn - NODE_DATA(page_to_nid(page))->node_start_pfn;
	return base + offset;
	}

	static int __init alloc_node_page_cgroup(int nid)
	{
	struct page_cgroup base, pc;
	unsigned long table_size;
	unsigned long start_pfn, nr_pages, index;

	start_pfn = NODE_DATA(nid)->node_start_pfn;
	nr_pages = NODE_DATA(nid)->node_spanned_pages;

	if (!nr_pages)
	return 0;

	table_size = sizeof(struct page_cgroup) * nr_pages;

	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
	table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
	if (!base)
	return -ENOMEM;
	for (index = 0; index < nr_pages; index++) {
	pc = base + index;
	__init_page_cgroup(pc, start_pfn + index);
	}
	NODE_DATA(nid)->node_page_cgroup = base;
	total_usage += table_size;
	return 0;
	}

	void __init page_cgroup_init(void)
	{

	int nid, fail;

	if (mem_cgroup_subsys.disabled)
	return;

	for_each_online_node(nid) {
	fail = alloc_node_page_cgroup(nid);
	if (fail)
	goto fail;
	}
	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
	printk(KERN_INFO "please try cgroup_disable=memory option if you"
	" don't want\n");
	return;
	fail:
	printk(KERN_CRIT "allocation of page_cgroup was failed.\n");
	printk(KERN_CRIT "please try cgroup_disable=memory boot option\n");
	panic("Out of memory");
	}

	#else /* CONFIG_FLAT_NODE_MEM_MAP */

	struct page_cgroup lookup_page_cgroup(struct page page)
	{
	unsigned long pfn = page_to_pfn(page);
	struct mem_section *section = __pfn_to_section(pfn);

	return section->page_cgroup + pfn;
	}

	/* __alloc_bootmem...() is protected by !slab_available() */
	static int __init_refok init_section_page_cgroup(unsigned long pfn)
	{
	struct mem_section *section = __pfn_to_section(pfn);
	struct page_cgroup base, pc;
	unsigned long table_size;
	int nid, index;

	if (!section->page_cgroup) {
	nid = page_to_nid(pfn_to_page(pfn));
	table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
	if (slab_is_available()) {
	base = kmalloc_node(table_size, GFP_KERNEL, nid);
	if (!base)
	base = vmalloc_node(table_size, nid);
	} else {
	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
	table_size,
	PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
	}
	} else {
	/*
	* We don't have to allocate page_cgroup again, but
	* address of memmap may be changed. So, we have to initialize
	* again.
	*/
	base = section->page_cgroup + pfn;
	table_size = 0;
	/* check address of memmap is changed or not. */
	if (base->page == pfn_to_page(pfn))
	return 0;
	}

	if (!base) {
	printk(KERN_ERR "page cgroup allocation failure\n");
	return -ENOMEM;
	}

	for (index = 0; index < PAGES_PER_SECTION; index++) {
	pc = base + index;
	__init_page_cgroup(pc, pfn + index);
	}

	section->page_cgroup = base - pfn;
	total_usage += table_size;
	return 0;
	}
	#ifdef CONFIG_MEMORY_HOTPLUG
	void __free_page_cgroup(unsigned long pfn)
	{
	struct mem_section *ms;
	struct page_cgroup *base;

	ms = __pfn_to_section(pfn);
	if (!ms \|\| !ms->page_cgroup)
	return;
	base = ms->page_cgroup + pfn;
	if (is_vmalloc_addr(base)) {
	vfree(base);
	ms->page_cgroup = NULL;
	} else {
	struct page *page = virt_to_page(base);
	if (!PageReserved(page)) { /* Is bootmem ? */
	kfree(base);
	ms->page_cgroup = NULL;
	}
	}
	}

	int __meminit online_page_cgroup(unsigned long start_pfn,
	unsigned long nr_pages,
	int nid)
	{
	unsigned long start, end, pfn;
	int fail = 0;

	start = start_pfn & ~(PAGES_PER_SECTION - 1);
	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);

	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
	if (!pfn_present(pfn))
	continue;
	fail = init_section_page_cgroup(pfn);
	}
	if (!fail)
	return 0;

	/* rollback */
	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
	__free_page_cgroup(pfn);

	return -ENOMEM;
	}

	int __meminit offline_page_cgroup(unsigned long start_pfn,
	unsigned long nr_pages, int nid)
	{
	unsigned long start, end, pfn;

	start = start_pfn & ~(PAGES_PER_SECTION - 1);
	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);

	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
	__free_page_cgroup(pfn);
	return 0;

	}

	static int __meminit page_cgroup_callback(struct notifier_block *self,
	unsigned long action, void *arg)
	{
	struct memory_notify *mn = arg;
	int ret = 0;
	switch (action) {
	case MEM_GOING_ONLINE:
	ret = online_page_cgroup(mn->start_pfn,
	mn->nr_pages, mn->status_change_nid);
	break;
	case MEM_OFFLINE:
	offline_page_cgroup(mn->start_pfn,
	mn->nr_pages, mn->status_change_nid);
	break;
	case MEM_CANCEL_ONLINE:
	case MEM_GOING_OFFLINE:
	break;
	case MEM_ONLINE:
	case MEM_CANCEL_OFFLINE:
	break;
	}

	if (ret)
	ret = notifier_from_errno(ret);
	else
	ret = NOTIFY_OK;

	return ret;
	}

	#endif

	void __init page_cgroup_init(void)
	{
	unsigned long pfn;
	int fail = 0;

	if (mem_cgroup_subsys.disabled)
	return;

	for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
	if (!pfn_present(pfn))
	continue;
	fail = init_section_page_cgroup(pfn);
	}
	if (fail) {
	printk(KERN_CRIT "try cgroup_disable=memory boot option\n");
	panic("Out of memory");
	} else {
	hotplug_memory_notifier(page_cgroup_callback, 0);
	}
	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
	printk(KERN_INFO "please try cgroup_disable=memory option if you don't"
	" want\n");
	}

	void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
	{
	return;
	}

	#endif


	#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP

	static DEFINE_MUTEX(swap_cgroup_mutex);
	struct swap_cgroup_ctrl {
	struct page **map;
	unsigned long length;
	};

	struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];

	/*
	* This 8bytes seems big..maybe we can reduce this when we can use "id" for
	* cgroup rather than pointer.
	*/
	struct swap_cgroup {
	struct mem_cgroup *val;
	};
	#define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup))
	#define SC_POS_MASK (SC_PER_PAGE - 1)

	/*
	* SwapCgroup implements "lookup" and "exchange" operations.
	* In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
	* against SwapCache. At swap_free(), this is accessed directly from swap.
	*
	* This means,
	* - we have no race in "exchange" when we're accessed via SwapCache because
	* SwapCache(and its swp_entry) is under lock.
	* - When called via swap_free(), there is no user of this entry and no race.
	* Then, we don't need lock around "exchange".
	*
	* TODO: we can push these buffers out to HIGHMEM.
	*/

	/*
	* allocate buffer for swap_cgroup.
	*/
	static int swap_cgroup_prepare(int type)
	{
	struct page *page;
	struct swap_cgroup_ctrl *ctrl;
	unsigned long idx, max;

	if (!do_swap_account)
	return 0;
	ctrl = &swap_cgroup_ctrl[type];

	for (idx = 0; idx < ctrl->length; idx++) {
	page = alloc_page(GFP_KERNEL \| __GFP_ZERO);
	if (!page)
	goto not_enough_page;
	ctrl->map[idx] = page;
	}
	return 0;
	not_enough_page:
	max = idx;
	for (idx = 0; idx < max; idx++)
	__free_page(ctrl->map[idx]);

	return -ENOMEM;
	}

	/**
	* swap_cgroup_record - record mem_cgroup for this swp_entry.
	* @ent: swap entry to be recorded into
	* @mem: mem_cgroup to be recorded
	*
	* Returns old value at success, NULL at failure.
	* (Of course, old value can be NULL.)
	*/
	struct mem_cgroup swap_cgroup_record(swp_entry_t ent, struct mem_cgroup mem)
	{
	int type = swp_type(ent);
	unsigned long offset = swp_offset(ent);
	unsigned long idx = offset / SC_PER_PAGE;
	unsigned long pos = offset & SC_POS_MASK;
	struct swap_cgroup_ctrl *ctrl;
	struct page *mappage;
	struct swap_cgroup *sc;
	struct mem_cgroup *old;

	if (!do_swap_account)
	return NULL;

	ctrl = &swap_cgroup_ctrl[type];

	mappage = ctrl->map[idx];
	sc = page_address(mappage);
	sc += pos;
	old = sc->val;
	sc->val = mem;

	return old;
	}

	/**
	* lookup_swap_cgroup - lookup mem_cgroup tied to swap entry
	* @ent: swap entry to be looked up.
	*
	* Returns pointer to mem_cgroup at success. NULL at failure.
	*/
	struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
	{
	int type = swp_type(ent);
	unsigned long offset = swp_offset(ent);
	unsigned long idx = offset / SC_PER_PAGE;
	unsigned long pos = offset & SC_POS_MASK;
	struct swap_cgroup_ctrl *ctrl;
	struct page *mappage;
	struct swap_cgroup *sc;
	struct mem_cgroup *ret;

	if (!do_swap_account)
	return NULL;

	ctrl = &swap_cgroup_ctrl[type];
	mappage = ctrl->map[idx];
	sc = page_address(mappage);
	sc += pos;
	ret = sc->val;
	return ret;
	}

	int swap_cgroup_swapon(int type, unsigned long max_pages)
	{
	void *array;
	unsigned long array_size;
	unsigned long length;
	struct swap_cgroup_ctrl *ctrl;

	if (!do_swap_account)
	return 0;

	length = ((max_pages/SC_PER_PAGE) + 1);
	array_size = length * sizeof(void *);

	array = vmalloc(array_size);
	if (!array)
	goto nomem;

	memset(array, 0, array_size);
	ctrl = &swap_cgroup_ctrl[type];
	mutex_lock(&swap_cgroup_mutex);
	ctrl->length = length;
	ctrl->map = array;
	if (swap_cgroup_prepare(type)) {
	/* memory shortage */
	ctrl->map = NULL;
	ctrl->length = 0;
	vfree(array);
	mutex_unlock(&swap_cgroup_mutex);
	goto nomem;
	}
	mutex_unlock(&swap_cgroup_mutex);

	printk(KERN_INFO
	"swap_cgroup: uses %ld bytes of vmalloc for pointer array space"
	" and %ld bytes to hold mem_cgroup pointers on swap\n",
	array_size, length * PAGE_SIZE);
	printk(KERN_INFO
	"swap_cgroup can be disabled by noswapaccount boot option.\n");

	return 0;
	nomem:
	printk(KERN_INFO "couldn't allocate enough memory for swap_cgroup.\n");
	printk(KERN_INFO
	"swap_cgroup can be disabled by noswapaccount boot option\n");
	return -ENOMEM;
	}

	void swap_cgroup_swapoff(int type)
	{
	int i;
	struct swap_cgroup_ctrl *ctrl;

	if (!do_swap_account)
	return;

	mutex_lock(&swap_cgroup_mutex);
	ctrl = &swap_cgroup_ctrl[type];
	if (ctrl->map) {
	for (i = 0; i < ctrl->length; i++) {
	struct page *page = ctrl->map[i];
	if (page)
	__free_page(page);
	}
	vfree(ctrl->map);
	ctrl->map = NULL;
	ctrl->length = 0;
	}
	mutex_unlock(&swap_cgroup_mutex);
	}

	#endif