drivers/base/memory.c - kernel/common - Git at Google

 /*
  * Memory subsystem support
  *
  * Written by Matt Tolentino <[email protected]>
  *            Dave Hansen <[email protected]>
  *
  * This file provides the necessary infrastructure to represent
  * a SPARSEMEM-memory-model system's physical memory in /sysfs.
  * All arch-independent code that assumes MEMORY_HOTPLUG requires
  * SPARSEMEM should be contained here, or in mm/memory_hotplug.c.
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/topology.h>
 #include <linux/capability.h>
 #include <linux/device.h>
 #include <linux/memory.h>
 #include <linux/kobject.h>
 #include <linux/memory_hotplug.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/stat.h>
 #include <linux/slab.h>

 #include <linux/atomic.h>
 #include <asm/uaccess.h>

 static DEFINE_MUTEX(mem_sysfs_mutex);

 #define MEMORY_CLASS_NAME	"memory"

 static int sections_per_block;

 static inline int base_memory_block_id(int section_nr)
 {
 	return section_nr / sections_per_block;
 }

 static struct bus_type memory_subsys = {
 	.name = MEMORY_CLASS_NAME,
 	.dev_name = MEMORY_CLASS_NAME,
 };

 static BLOCKING_NOTIFIER_HEAD(memory_chain);

 int register_memory_notifier(struct notifier_block *nb)
 {
         return blocking_notifier_chain_register(&memory_chain, nb);
 }
 EXPORT_SYMBOL(register_memory_notifier);

 void unregister_memory_notifier(struct notifier_block *nb)
 {
         blocking_notifier_chain_unregister(&memory_chain, nb);
 }
 EXPORT_SYMBOL(unregister_memory_notifier);

 static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);

 int register_memory_isolate_notifier(struct notifier_block *nb)
 {
 	return atomic_notifier_chain_register(&memory_isolate_chain, nb);
 }
 EXPORT_SYMBOL(register_memory_isolate_notifier);

 void unregister_memory_isolate_notifier(struct notifier_block *nb)
 {
 	atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
 }
 EXPORT_SYMBOL(unregister_memory_isolate_notifier);

 static void memory_block_release(struct device *dev)
 {
 	struct memory_block *mem = container_of(dev, struct memory_block, dev);

 	kfree(mem);
 }

 /*
  * register_memory - Setup a sysfs device for a memory block
  */
 static
 int register_memory(struct memory_block *memory)
 {
 	int error;

 	memory->dev.bus = &memory_subsys;
 	memory->dev.id = memory->start_section_nr / sections_per_block;
 	memory->dev.release = memory_block_release;

 	error = device_register(&memory->dev);
 	return error;
 }

 unsigned long __weak memory_block_size_bytes(void)
 {
 	return MIN_MEMORY_BLOCK_SIZE;
 }

 static unsigned long get_memory_block_size(void)
 {
 	unsigned long block_sz;

 	block_sz = memory_block_size_bytes();

 	/* Validate blk_sz is a power of 2 and not less than section size */
 	if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
 		WARN_ON(1);
 		block_sz = MIN_MEMORY_BLOCK_SIZE;
 	}

 	return block_sz;
 }

 /*
  * use this as the physical section index that this memsection
  * uses.
  */

 static ssize_t show_mem_start_phys_index(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, dev);
 	unsigned long phys_index;

 	phys_index = mem->start_section_nr / sections_per_block;
 	return sprintf(buf, "%08lx\n", phys_index);
 }

 static ssize_t show_mem_end_phys_index(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, dev);
 	unsigned long phys_index;

 	phys_index = mem->end_section_nr / sections_per_block;
 	return sprintf(buf, "%08lx\n", phys_index);
 }

 /*
  * Show whether the section of memory is likely to be hot-removable
  */
 static ssize_t show_mem_removable(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	unsigned long i, pfn;
 	int ret = 1;
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, dev);

 	for (i = 0; i < sections_per_block; i++) {
 		pfn = section_nr_to_pfn(mem->start_section_nr + i);
 		ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
 	}

 	return sprintf(buf, "%d\n", ret);
 }

 /*
  * online, offline, going offline, etc.
  */
 static ssize_t show_mem_state(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, dev);
 	ssize_t len = 0;

 	/*
 	 * We can probably put these states in a nice little array
 	 * so that they're not open-coded
 	 */
 	switch (mem->state) {
 		case MEM_ONLINE:
 			len = sprintf(buf, "online\n");
 			break;
 		case MEM_OFFLINE:
 			len = sprintf(buf, "offline\n");
 			break;
 		case MEM_GOING_OFFLINE:
 			len = sprintf(buf, "going-offline\n");
 			break;
 		default:
 			len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
 					mem->state);
 			WARN_ON(1);
 			break;
 	}

 	return len;
 }

 int memory_notify(unsigned long val, void *v)
 {
 	return blocking_notifier_call_chain(&memory_chain, val, v);
 }

 int memory_isolate_notify(unsigned long val, void *v)
 {
 	return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
 }

 /*
  * The probe routines leave the pages reserved, just as the bootmem code does.
  * Make sure they're still that way.
  */
 static bool pages_correctly_reserved(unsigned long start_pfn)
 {
 	int i, j;
 	struct page *page;
 	unsigned long pfn = start_pfn;

 	/*
 	 * memmap between sections is not contiguous except with
 	 * SPARSEMEM_VMEMMAP. We lookup the page once per section
 	 * and assume memmap is contiguous within each section
 	 */
 	for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
 		if (WARN_ON_ONCE(!pfn_valid(pfn)))
 			return false;
 		page = pfn_to_page(pfn);

 		for (j = 0; j < PAGES_PER_SECTION; j++) {
 			if (PageReserved(page + j))
 				continue;

 			printk(KERN_WARNING "section number %ld page number %d "
 				"not reserved, was it already online?\n",
 				pfn_to_section_nr(pfn), j);

 			return false;
 		}
 	}

 	return true;
 }

 /*
  * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
  * OK to have direct references to sparsemem variables in here.
  */
 static int
 memory_block_action(unsigned long phys_index, unsigned long action, int online_type)
 {
 	unsigned long start_pfn;
 	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 	struct page *first_page;
 	int ret;

 	first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
 	start_pfn = page_to_pfn(first_page);

 	switch (action) {
 		case MEM_ONLINE:
 			if (!pages_correctly_reserved(start_pfn))
 				return -EBUSY;

 			ret = online_pages(start_pfn, nr_pages, online_type);
 			break;
 		case MEM_OFFLINE:
 			ret = offline_pages(start_pfn, nr_pages);
 			break;
 		default:
 			WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
 			     "%ld\n", __func__, phys_index, action, action);
 			ret = -EINVAL;
 	}

 	return ret;
 }

 static int __memory_block_change_state(struct memory_block *mem,
 		unsigned long to_state, unsigned long from_state_req,
 		int online_type)
 {
 	int ret = 0;

 	if (mem->state != from_state_req) {
 		ret = -EINVAL;
 		goto out;
 	}

 	if (to_state == MEM_OFFLINE)
 		mem->state = MEM_GOING_OFFLINE;

 	ret = memory_block_action(mem->start_section_nr, to_state, online_type);

 	if (ret) {
 		mem->state = from_state_req;
 		goto out;
 	}

 	mem->state = to_state;
 	switch (mem->state) {
 	case MEM_OFFLINE:
 		kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
 		break;
 	case MEM_ONLINE:
 		kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
 		break;
 	default:
 		break;
 	}
 out:
 	return ret;
 }

 static int memory_block_change_state(struct memory_block *mem,
 		unsigned long to_state, unsigned long from_state_req,
 		int online_type)
 {
 	int ret;

 	mutex_lock(&mem->state_mutex);
 	ret = __memory_block_change_state(mem, to_state, from_state_req,
 					  online_type);
 	mutex_unlock(&mem->state_mutex);

 	return ret;
 }
 static ssize_t
 store_mem_state(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
 	struct memory_block *mem;
 	int ret = -EINVAL;

 	mem = container_of(dev, struct memory_block, dev);

 	if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_KERNEL);
 	else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_MOVABLE);
 	else if (!strncmp(buf, "online", min_t(int, count, 6)))
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_KEEP);
 	else if(!strncmp(buf, "offline", min_t(int, count, 7)))
 		ret = memory_block_change_state(mem, MEM_OFFLINE,
 						MEM_ONLINE, -1);

 	if (ret)
 		return ret;
 	return count;
 }

 /*
  * phys_device is a bad name for this.  What I really want
  * is a way to differentiate between memory ranges that
  * are part of physical devices that constitute
  * a complete removable unit or fru.
  * i.e. do these ranges belong to the same physical device,
  * s.t. if I offline all of these sections I can then
  * remove the physical device?
  */
 static ssize_t show_phys_device(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, dev);
 	return sprintf(buf, "%d\n", mem->phys_device);
 }

 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 static DEVICE_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);

 #define mem_create_simple_file(mem, attr_name)	\
 	device_create_file(&mem->dev, &dev_attr_##attr_name)
 #define mem_remove_simple_file(mem, attr_name)	\
 	device_remove_file(&mem->dev, &dev_attr_##attr_name)

 /*
  * Block size attribute stuff
  */
 static ssize_t
 print_block_size(struct device *dev, struct device_attribute *attr,
 		 char *buf)
 {
 	return sprintf(buf, "%lx\n", get_memory_block_size());
 }

 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);

 static int block_size_init(void)
 {
 	return device_create_file(memory_subsys.dev_root,
 				  &dev_attr_block_size_bytes);
 }

 /*
  * Some architectures will have custom drivers to do this, and
  * will not need to do it from userspace.  The fake hot-add code
  * as well as ppc64 will do all of their discovery in userspace
  * and will require this interface.
  */
 #ifdef CONFIG_ARCH_MEMORY_PROBE
 static ssize_t
 memory_probe_store(struct device *dev, struct device_attribute *attr,
 		   const char *buf, size_t count)
 {
 	u64 phys_addr;
 	int nid;
 	int i, ret;
 	unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;

 	phys_addr = simple_strtoull(buf, NULL, 0);

 	if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 		return -EINVAL;

 	for (i = 0; i < sections_per_block; i++) {
 		nid = memory_add_physaddr_to_nid(phys_addr);
 		ret = add_memory(nid, phys_addr,
 				 PAGES_PER_SECTION << PAGE_SHIFT);
 		if (ret)
 			goto out;

 		phys_addr += MIN_MEMORY_BLOCK_SIZE;
 	}

 	ret = count;
 out:
 	return ret;
 }
 static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);

 static int memory_probe_init(void)
 {
 	return device_create_file(memory_subsys.dev_root, &dev_attr_probe);
 }
 #else
 static inline int memory_probe_init(void)
 {
 	return 0;
 }
 #endif

 #ifdef CONFIG_MEMORY_FAILURE
 /*
  * Support for offlining pages of memory
  */

 /* Soft offline a page */
 static ssize_t
 store_soft_offline_page(struct device *dev,
 			struct device_attribute *attr,
 			const char *buf, size_t count)
 {
 	int ret;
 	u64 pfn;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (strict_strtoull(buf, 0, &pfn) < 0)
 		return -EINVAL;
 	pfn >>= PAGE_SHIFT;
 	if (!pfn_valid(pfn))
 		return -ENXIO;
 	ret = soft_offline_page(pfn_to_page(pfn), 0);
 	return ret == 0 ? count : ret;
 }

 /* Forcibly offline a page, including killing processes. */
 static ssize_t
 store_hard_offline_page(struct device *dev,
 			struct device_attribute *attr,
 			const char *buf, size_t count)
 {
 	int ret;
 	u64 pfn;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (strict_strtoull(buf, 0, &pfn) < 0)
 		return -EINVAL;
 	pfn >>= PAGE_SHIFT;
 	ret = memory_failure(pfn, 0, 0);
 	return ret ? ret : count;
 }

 static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
 static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);

 static __init int memory_fail_init(void)
 {
 	int err;

 	err = device_create_file(memory_subsys.dev_root,
 				&dev_attr_soft_offline_page);
 	if (!err)
 		err = device_create_file(memory_subsys.dev_root,
 				&dev_attr_hard_offline_page);
 	return err;
 }
 #else
 static inline int memory_fail_init(void)
 {
 	return 0;
 }
 #endif

 /*
  * Note that phys_device is optional.  It is here to allow for
  * differentiation between which *physical* devices each
  * section belongs to...
  */
 int __weak arch_get_memory_phys_device(unsigned long start_pfn)
 {
 	return 0;
 }

 /*
  * A reference for the returned object is held and the reference for the
  * hinted object is released.
  */
 struct memory_block *find_memory_block_hinted(struct mem_section *section,
 					      struct memory_block *hint)
 {
 	int block_id = base_memory_block_id(__section_nr(section));
 	struct device *hintdev = hint ? &hint->dev : NULL;
 	struct device *dev;

 	dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
 	if (hint)
 		put_device(&hint->dev);
 	if (!dev)
 		return NULL;
 	return container_of(dev, struct memory_block, dev);
 }

 /*
  * For now, we have a linear search to go find the appropriate
  * memory_block corresponding to a particular phys_index. If
  * this gets to be a real problem, we can always use a radix
  * tree or something here.
  *
  * This could be made generic for all device subsystems.
  */
 struct memory_block *find_memory_block(struct mem_section *section)
 {
 	return find_memory_block_hinted(section, NULL);
 }

 static int init_memory_block(struct memory_block **memory,
 			     struct mem_section *section, unsigned long state)
 {
 	struct memory_block *mem;
 	unsigned long start_pfn;
 	int scn_nr;
 	int ret = 0;

 	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 	if (!mem)
 		return -ENOMEM;

 	scn_nr = __section_nr(section);
 	mem->start_section_nr =
 			base_memory_block_id(scn_nr) * sections_per_block;
 	mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 	mem->state = state;
 	mem->section_count++;
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->start_section_nr);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);

 	ret = register_memory(mem);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_index);
 	if (!ret)
 		ret = mem_create_simple_file(mem, end_phys_index);
 	if (!ret)
 		ret = mem_create_simple_file(mem, state);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_device);
 	if (!ret)
 		ret = mem_create_simple_file(mem, removable);

 	*memory = mem;
 	return ret;
 }

 static int add_memory_section(int nid, struct mem_section *section,
 			struct memory_block **mem_p,
 			unsigned long state, enum mem_add_context context)
 {
 	struct memory_block *mem = NULL;
 	int scn_nr = __section_nr(section);
 	int ret = 0;

 	mutex_lock(&mem_sysfs_mutex);

 	if (context == BOOT) {
 		/* same memory block ? */
 		if (mem_p && *mem_p)
 			if (scn_nr >= (*mem_p)->start_section_nr &&
 			    scn_nr <= (*mem_p)->end_section_nr) {
 				mem = *mem_p;
 				kobject_get(&mem->dev.kobj);
 			}
 	} else
 		mem = find_memory_block(section);

 	if (mem) {
 		mem->section_count++;
 		kobject_put(&mem->dev.kobj);
 	} else {
 		ret = init_memory_block(&mem, section, state);
 		/* store memory_block pointer for next loop */
 		if (!ret && context == BOOT)
 			if (mem_p)
 				*mem_p = mem;
 	}

 	if (!ret) {
 		if (context == HOTPLUG &&
 		    mem->section_count == sections_per_block)
 			ret = register_mem_sect_under_node(mem, nid);
 	}

 	mutex_unlock(&mem_sysfs_mutex);
 	return ret;
 }

 /*
  * need an interface for the VM to add new memory regions,
  * but without onlining it.
  */
 int register_new_memory(int nid, struct mem_section *section)
 {
 	return add_memory_section(nid, section, NULL, MEM_OFFLINE, HOTPLUG);
 }

 #ifdef CONFIG_MEMORY_HOTREMOVE
 static void
 unregister_memory(struct memory_block *memory)
 {
 	BUG_ON(memory->dev.bus != &memory_subsys);

 	/* drop the ref. we got in remove_memory_block() */
 	kobject_put(&memory->dev.kobj);
 	device_unregister(&memory->dev);
 }

 static int remove_memory_block(unsigned long node_id,
 			       struct mem_section *section, int phys_device)
 {
 	struct memory_block *mem;

 	mutex_lock(&mem_sysfs_mutex);
 	mem = find_memory_block(section);
 	unregister_mem_sect_under_nodes(mem, __section_nr(section));

 	mem->section_count--;
 	if (mem->section_count == 0) {
 		mem_remove_simple_file(mem, phys_index);
 		mem_remove_simple_file(mem, end_phys_index);
 		mem_remove_simple_file(mem, state);
 		mem_remove_simple_file(mem, phys_device);
 		mem_remove_simple_file(mem, removable);
 		unregister_memory(mem);
 	} else
 		kobject_put(&mem->dev.kobj);

 	mutex_unlock(&mem_sysfs_mutex);
 	return 0;
 }

 int unregister_memory_section(struct mem_section *section)
 {
 	if (!present_section(section))
 		return -EINVAL;

 	return remove_memory_block(0, section, 0);
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */

 /*
  * offline one memory block. If the memory block has been offlined, do nothing.
  */
 int offline_memory_block(struct memory_block *mem)
 {
 	int ret = 0;

 	mutex_lock(&mem->state_mutex);
 	if (mem->state != MEM_OFFLINE)
 		ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
 	mutex_unlock(&mem->state_mutex);

 	return ret;
 }

 /* return true if the memory block is offlined, otherwise, return false */
 bool is_memblock_offlined(struct memory_block *mem)
 {
 	return mem->state == MEM_OFFLINE;
 }

 /*
  * Initialize the sysfs support for memory devices...
  */
 int __init memory_dev_init(void)
 {
 	unsigned int i;
 	int ret;
 	int err;
 	unsigned long block_sz;
 	struct memory_block *mem = NULL;

 	ret = subsys_system_register(&memory_subsys, NULL);
 	if (ret)
 		goto out;

 	block_sz = get_memory_block_size();
 	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;

 	/*
 	 * Create entries for memory sections that were found
 	 * during boot and have been initialized
 	 */
 	for (i = 0; i < NR_MEM_SECTIONS; i++) {
 		if (!present_section_nr(i))
 			continue;
 		/* don't need to reuse memory_block if only one per block */
 		err = add_memory_section(0, __nr_to_section(i),
 				 (sections_per_block == 1) ? NULL : &mem,
 					 MEM_ONLINE,
 					 BOOT);
 		if (!ret)
 			ret = err;
 	}

 	err = memory_probe_init();
 	if (!ret)
 		ret = err;
 	err = memory_fail_init();
 	if (!ret)
 		ret = err;
 	err = block_size_init();
 	if (!ret)
 		ret = err;
 out:
 	if (ret)
 		printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
 	return ret;
 }
	/*
	* Memory subsystem support
	*
	* Written by Matt Tolentino <[email protected]>
	* Dave Hansen <[email protected]>
	*
	* This file provides the necessary infrastructure to represent
	* a SPARSEMEM-memory-model system's physical memory in /sysfs.
	* All arch-independent code that assumes MEMORY_HOTPLUG requires
	* SPARSEMEM should be contained here, or in mm/memory_hotplug.c.
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/topology.h>
	#include <linux/capability.h>
	#include <linux/device.h>
	#include <linux/memory.h>
	#include <linux/kobject.h>
	#include <linux/memory_hotplug.h>
	#include <linux/mm.h>
	#include <linux/mutex.h>
	#include <linux/stat.h>
	#include <linux/slab.h>

	#include <linux/atomic.h>
	#include <asm/uaccess.h>

	static DEFINE_MUTEX(mem_sysfs_mutex);

	#define MEMORY_CLASS_NAME "memory"

	static int sections_per_block;

	static inline int base_memory_block_id(int section_nr)
	{
	return section_nr / sections_per_block;
	}

	static struct bus_type memory_subsys = {
	.name = MEMORY_CLASS_NAME,
	.dev_name = MEMORY_CLASS_NAME,
	};

	static BLOCKING_NOTIFIER_HEAD(memory_chain);

	int register_memory_notifier(struct notifier_block *nb)
	{
	return blocking_notifier_chain_register(&memory_chain, nb);
	}
	EXPORT_SYMBOL(register_memory_notifier);

	void unregister_memory_notifier(struct notifier_block *nb)
	{
	blocking_notifier_chain_unregister(&memory_chain, nb);
	}
	EXPORT_SYMBOL(unregister_memory_notifier);

	static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);

	int register_memory_isolate_notifier(struct notifier_block *nb)
	{
	return atomic_notifier_chain_register(&memory_isolate_chain, nb);
	}
	EXPORT_SYMBOL(register_memory_isolate_notifier);

	void unregister_memory_isolate_notifier(struct notifier_block *nb)
	{
	atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
	}
	EXPORT_SYMBOL(unregister_memory_isolate_notifier);

	static void memory_block_release(struct device *dev)
	{
	struct memory_block *mem = container_of(dev, struct memory_block, dev);

	kfree(mem);
	}

	/*
	* register_memory - Setup a sysfs device for a memory block
	*/
	static
	int register_memory(struct memory_block *memory)
	{
	int error;

	memory->dev.bus = &memory_subsys;
	memory->dev.id = memory->start_section_nr / sections_per_block;
	memory->dev.release = memory_block_release;

	error = device_register(&memory->dev);
	return error;
	}

	unsigned long __weak memory_block_size_bytes(void)
	{
	return MIN_MEMORY_BLOCK_SIZE;
	}

	static unsigned long get_memory_block_size(void)
	{
	unsigned long block_sz;

	block_sz = memory_block_size_bytes();

	/* Validate blk_sz is a power of 2 and not less than section size */
	if ((block_sz & (block_sz - 1)) \|\| (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
	WARN_ON(1);
	block_sz = MIN_MEMORY_BLOCK_SIZE;
	}

	return block_sz;
	}

	/*
	* use this as the physical section index that this memsection
	* uses.
	*/

	static ssize_t show_mem_start_phys_index(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct memory_block *mem =
	container_of(dev, struct memory_block, dev);
	unsigned long phys_index;

	phys_index = mem->start_section_nr / sections_per_block;
	return sprintf(buf, "%08lx\n", phys_index);
	}

	static ssize_t show_mem_end_phys_index(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct memory_block *mem =
	container_of(dev, struct memory_block, dev);
	unsigned long phys_index;

	phys_index = mem->end_section_nr / sections_per_block;
	return sprintf(buf, "%08lx\n", phys_index);
	}

	/*
	* Show whether the section of memory is likely to be hot-removable
	*/
	static ssize_t show_mem_removable(struct device *dev,
	struct device_attribute attr, char buf)
	{
	unsigned long i, pfn;
	int ret = 1;
	struct memory_block *mem =
	container_of(dev, struct memory_block, dev);

	for (i = 0; i < sections_per_block; i++) {
	pfn = section_nr_to_pfn(mem->start_section_nr + i);
	ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
	}

	return sprintf(buf, "%d\n", ret);
	}

	/*
	* online, offline, going offline, etc.
	*/
	static ssize_t show_mem_state(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct memory_block *mem =
	container_of(dev, struct memory_block, dev);
	ssize_t len = 0;

	/*
	* We can probably put these states in a nice little array
	* so that they're not open-coded
	*/
	switch (mem->state) {
	case MEM_ONLINE:
	len = sprintf(buf, "online\n");
	break;
	case MEM_OFFLINE:
	len = sprintf(buf, "offline\n");
	break;
	case MEM_GOING_OFFLINE:
	len = sprintf(buf, "going-offline\n");
	break;
	default:
	len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
	mem->state);
	WARN_ON(1);
	break;
	}

	return len;
	}

	int memory_notify(unsigned long val, void *v)
	{
	return blocking_notifier_call_chain(&memory_chain, val, v);
	}

	int memory_isolate_notify(unsigned long val, void *v)
	{
	return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
	}

	/*
	* The probe routines leave the pages reserved, just as the bootmem code does.
	* Make sure they're still that way.
	*/
	static bool pages_correctly_reserved(unsigned long start_pfn)
	{
	int i, j;
	struct page *page;
	unsigned long pfn = start_pfn;

	/*
	* memmap between sections is not contiguous except with
	* SPARSEMEM_VMEMMAP. We lookup the page once per section
	* and assume memmap is contiguous within each section
	*/
	for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
	if (WARN_ON_ONCE(!pfn_valid(pfn)))
	return false;
	page = pfn_to_page(pfn);

	for (j = 0; j < PAGES_PER_SECTION; j++) {
	if (PageReserved(page + j))
	continue;

	printk(KERN_WARNING "section number %ld page number %d "
	"not reserved, was it already online?\n",
	pfn_to_section_nr(pfn), j);

	return false;
	}
	}

	return true;
	}

	/*
	* MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
	* OK to have direct references to sparsemem variables in here.
	*/
	static int
	memory_block_action(unsigned long phys_index, unsigned long action, int online_type)
	{
	unsigned long start_pfn;
	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
	struct page *first_page;
	int ret;

	first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
	start_pfn = page_to_pfn(first_page);

	switch (action) {
	case MEM_ONLINE:
	if (!pages_correctly_reserved(start_pfn))
	return -EBUSY;

	ret = online_pages(start_pfn, nr_pages, online_type);
	break;
	case MEM_OFFLINE:
	ret = offline_pages(start_pfn, nr_pages);
	break;
	default:
	WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
	"%ld\n", __func__, phys_index, action, action);
	ret = -EINVAL;
	}

	return ret;
	}

	static int __memory_block_change_state(struct memory_block *mem,
	unsigned long to_state, unsigned long from_state_req,
	int online_type)
	{
	int ret = 0;

	if (mem->state != from_state_req) {
	ret = -EINVAL;
	goto out;
	}

	if (to_state == MEM_OFFLINE)
	mem->state = MEM_GOING_OFFLINE;

	ret = memory_block_action(mem->start_section_nr, to_state, online_type);

	if (ret) {
	mem->state = from_state_req;
	goto out;
	}

	mem->state = to_state;
	switch (mem->state) {
	case MEM_OFFLINE:
	kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
	break;
	case MEM_ONLINE:
	kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
	break;
	default:
	break;
	}
	out:
	return ret;
	}

	static int memory_block_change_state(struct memory_block *mem,
	unsigned long to_state, unsigned long from_state_req,
	int online_type)
	{
	int ret;

	mutex_lock(&mem->state_mutex);
	ret = __memory_block_change_state(mem, to_state, from_state_req,
	online_type);
	mutex_unlock(&mem->state_mutex);

	return ret;
	}
	static ssize_t
	store_mem_state(struct device *dev,
	struct device_attribute attr, const char buf, size_t count)
	{
	struct memory_block *mem;
	int ret = -EINVAL;

	mem = container_of(dev, struct memory_block, dev);

	if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
	ret = memory_block_change_state(mem, MEM_ONLINE,
	MEM_OFFLINE, ONLINE_KERNEL);
	else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
	ret = memory_block_change_state(mem, MEM_ONLINE,
	MEM_OFFLINE, ONLINE_MOVABLE);
	else if (!strncmp(buf, "online", min_t(int, count, 6)))
	ret = memory_block_change_state(mem, MEM_ONLINE,
	MEM_OFFLINE, ONLINE_KEEP);
	else if(!strncmp(buf, "offline", min_t(int, count, 7)))
	ret = memory_block_change_state(mem, MEM_OFFLINE,
	MEM_ONLINE, -1);

	if (ret)
	return ret;
	return count;
	}

	/*
	* phys_device is a bad name for this. What I really want
	* is a way to differentiate between memory ranges that
	* are part of physical devices that constitute
	* a complete removable unit or fru.
	* i.e. do these ranges belong to the same physical device,
	* s.t. if I offline all of these sections I can then
	* remove the physical device?
	*/
	static ssize_t show_phys_device(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct memory_block *mem =
	container_of(dev, struct memory_block, dev);
	return sprintf(buf, "%d\n", mem->phys_device);
	}

	static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
	static DEVICE_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
	static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
	static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
	static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);

	#define mem_create_simple_file(mem, attr_name) \
	device_create_file(&mem->dev, &dev_attr_##attr_name)
	#define mem_remove_simple_file(mem, attr_name) \
	device_remove_file(&mem->dev, &dev_attr_##attr_name)

	/*
	* Block size attribute stuff
	*/
	static ssize_t
	print_block_size(struct device dev, struct device_attribute attr,
	char *buf)
	{
	return sprintf(buf, "%lx\n", get_memory_block_size());
	}

	static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);

	static int block_size_init(void)
	{
	return device_create_file(memory_subsys.dev_root,
	&dev_attr_block_size_bytes);
	}

	/*
	* Some architectures will have custom drivers to do this, and
	* will not need to do it from userspace. The fake hot-add code
	* as well as ppc64 will do all of their discovery in userspace
	* and will require this interface.
	*/
	#ifdef CONFIG_ARCH_MEMORY_PROBE
	static ssize_t
	memory_probe_store(struct device dev, struct device_attribute attr,
	const char *buf, size_t count)
	{
	u64 phys_addr;
	int nid;
	int i, ret;
	unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;

	phys_addr = simple_strtoull(buf, NULL, 0);

	if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
	return -EINVAL;

	for (i = 0; i < sections_per_block; i++) {
	nid = memory_add_physaddr_to_nid(phys_addr);
	ret = add_memory(nid, phys_addr,
	PAGES_PER_SECTION << PAGE_SHIFT);
	if (ret)
	goto out;

	phys_addr += MIN_MEMORY_BLOCK_SIZE;
	}

	ret = count;
	out:
	return ret;
	}
	static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);

	static int memory_probe_init(void)
	{
	return device_create_file(memory_subsys.dev_root, &dev_attr_probe);
	}
	#else
	static inline int memory_probe_init(void)
	{
	return 0;
	}
	#endif

	#ifdef CONFIG_MEMORY_FAILURE
	/*
	* Support for offlining pages of memory
	*/

	/* Soft offline a page */
	static ssize_t
	store_soft_offline_page(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	int ret;
	u64 pfn;
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;
	if (strict_strtoull(buf, 0, &pfn) < 0)
	return -EINVAL;
	pfn >>= PAGE_SHIFT;
	if (!pfn_valid(pfn))
	return -ENXIO;
	ret = soft_offline_page(pfn_to_page(pfn), 0);
	return ret == 0 ? count : ret;
	}

	/* Forcibly offline a page, including killing processes. */
	static ssize_t
	store_hard_offline_page(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	int ret;
	u64 pfn;
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;
	if (strict_strtoull(buf, 0, &pfn) < 0)
	return -EINVAL;
	pfn >>= PAGE_SHIFT;
	ret = memory_failure(pfn, 0, 0);
	return ret ? ret : count;
	}

	static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
	static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);

	static __init int memory_fail_init(void)
	{
	int err;

	err = device_create_file(memory_subsys.dev_root,
	&dev_attr_soft_offline_page);
	if (!err)
	err = device_create_file(memory_subsys.dev_root,
	&dev_attr_hard_offline_page);
	return err;
	}
	#else
	static inline int memory_fail_init(void)
	{
	return 0;
	}
	#endif

	/*
	* Note that phys_device is optional. It is here to allow for
	* differentiation between which physical devices each
	* section belongs to...
	*/
	int __weak arch_get_memory_phys_device(unsigned long start_pfn)
	{
	return 0;
	}

	/*
	* A reference for the returned object is held and the reference for the
	* hinted object is released.
	*/
	struct memory_block find_memory_block_hinted(struct mem_section section,
	struct memory_block *hint)
	{
	int block_id = base_memory_block_id(__section_nr(section));
	struct device *hintdev = hint ? &hint->dev : NULL;
	struct device *dev;

	dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
	if (hint)
	put_device(&hint->dev);
	if (!dev)
	return NULL;
	return container_of(dev, struct memory_block, dev);
	}

	/*
	* For now, we have a linear search to go find the appropriate
	* memory_block corresponding to a particular phys_index. If
	* this gets to be a real problem, we can always use a radix
	* tree or something here.
	*
	* This could be made generic for all device subsystems.
	*/
	struct memory_block find_memory_block(struct mem_section section)
	{
	return find_memory_block_hinted(section, NULL);
	}

	static int init_memory_block(struct memory_block **memory,
	struct mem_section *section, unsigned long state)
	{
	struct memory_block *mem;
	unsigned long start_pfn;
	int scn_nr;
	int ret = 0;

	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
	if (!mem)
	return -ENOMEM;

	scn_nr = __section_nr(section);
	mem->start_section_nr =
	base_memory_block_id(scn_nr) * sections_per_block;
	mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
	mem->state = state;
	mem->section_count++;
	mutex_init(&mem->state_mutex);
	start_pfn = section_nr_to_pfn(mem->start_section_nr);
	mem->phys_device = arch_get_memory_phys_device(start_pfn);

	ret = register_memory(mem);
	if (!ret)
	ret = mem_create_simple_file(mem, phys_index);
	if (!ret)
	ret = mem_create_simple_file(mem, end_phys_index);
	if (!ret)
	ret = mem_create_simple_file(mem, state);
	if (!ret)
	ret = mem_create_simple_file(mem, phys_device);
	if (!ret)
	ret = mem_create_simple_file(mem, removable);

	*memory = mem;
	return ret;
	}

	static int add_memory_section(int nid, struct mem_section *section,
	struct memory_block **mem_p,
	unsigned long state, enum mem_add_context context)
	{
	struct memory_block *mem = NULL;
	int scn_nr = __section_nr(section);
	int ret = 0;

	mutex_lock(&mem_sysfs_mutex);

	if (context == BOOT) {
	/* same memory block ? */
	if (mem_p && *mem_p)
	if (scn_nr >= (*mem_p)->start_section_nr &&
	scn_nr <= (*mem_p)->end_section_nr) {
	mem = *mem_p;
	kobject_get(&mem->dev.kobj);
	}
	} else
	mem = find_memory_block(section);

	if (mem) {
	mem->section_count++;
	kobject_put(&mem->dev.kobj);
	} else {
	ret = init_memory_block(&mem, section, state);
	/* store memory_block pointer for next loop */
	if (!ret && context == BOOT)
	if (mem_p)
	*mem_p = mem;
	}

	if (!ret) {
	if (context == HOTPLUG &&
	mem->section_count == sections_per_block)
	ret = register_mem_sect_under_node(mem, nid);
	}

	mutex_unlock(&mem_sysfs_mutex);
	return ret;
	}

	/*
	* need an interface for the VM to add new memory regions,
	* but without onlining it.
	*/
	int register_new_memory(int nid, struct mem_section *section)
	{
	return add_memory_section(nid, section, NULL, MEM_OFFLINE, HOTPLUG);
	}

	#ifdef CONFIG_MEMORY_HOTREMOVE
	static void
	unregister_memory(struct memory_block *memory)
	{
	BUG_ON(memory->dev.bus != &memory_subsys);

	/* drop the ref. we got in remove_memory_block() */
	kobject_put(&memory->dev.kobj);
	device_unregister(&memory->dev);
	}

	static int remove_memory_block(unsigned long node_id,
	struct mem_section *section, int phys_device)
	{
	struct memory_block *mem;

	mutex_lock(&mem_sysfs_mutex);
	mem = find_memory_block(section);
	unregister_mem_sect_under_nodes(mem, __section_nr(section));

	mem->section_count--;
	if (mem->section_count == 0) {
	mem_remove_simple_file(mem, phys_index);
	mem_remove_simple_file(mem, end_phys_index);
	mem_remove_simple_file(mem, state);
	mem_remove_simple_file(mem, phys_device);
	mem_remove_simple_file(mem, removable);
	unregister_memory(mem);
	} else
	kobject_put(&mem->dev.kobj);

	mutex_unlock(&mem_sysfs_mutex);
	return 0;
	}

	int unregister_memory_section(struct mem_section *section)
	{
	if (!present_section(section))
	return -EINVAL;

	return remove_memory_block(0, section, 0);
	}
	#endif /* CONFIG_MEMORY_HOTREMOVE */

	/*
	* offline one memory block. If the memory block has been offlined, do nothing.
	*/
	int offline_memory_block(struct memory_block *mem)
	{
	int ret = 0;

	mutex_lock(&mem->state_mutex);
	if (mem->state != MEM_OFFLINE)
	ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
	mutex_unlock(&mem->state_mutex);

	return ret;
	}

	/* return true if the memory block is offlined, otherwise, return false */
	bool is_memblock_offlined(struct memory_block *mem)
	{
	return mem->state == MEM_OFFLINE;
	}

	/*
	* Initialize the sysfs support for memory devices...
	*/
	int __init memory_dev_init(void)
	{
	unsigned int i;
	int ret;
	int err;
	unsigned long block_sz;
	struct memory_block *mem = NULL;

	ret = subsys_system_register(&memory_subsys, NULL);
	if (ret)
	goto out;

	block_sz = get_memory_block_size();
	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;

	/*
	* Create entries for memory sections that were found
	* during boot and have been initialized
	*/
	for (i = 0; i < NR_MEM_SECTIONS; i++) {
	if (!present_section_nr(i))
	continue;
	/* don't need to reuse memory_block if only one per block */
	err = add_memory_section(0, __nr_to_section(i),
	(sections_per_block == 1) ? NULL : &mem,
	MEM_ONLINE,
	BOOT);
	if (!ret)
	ret = err;
	}

	err = memory_probe_init();
	if (!ret)
	ret = err;
	err = memory_fail_init();
	if (!ret)
	ret = err;
	err = block_size_init();
	if (!ret)
	ret = err;
	out:
	if (ret)
	printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
	return ret;
	}