/*
 * Memory subsystem support
 *
 * Written by Matt Tolentino <matthew.e.tolentino@intel.com>
 *            Dave Hansen <haveblue@us.ibm.com>
 *
 * 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/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"

#define to_memory_block(dev) container_of(dev, struct memory_block, dev)

static int sections_per_block;

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

static int memory_subsys_online(struct device *dev);
static int memory_subsys_offline(struct device *dev);

static struct bus_type memory_subsys = {
        .name = MEMORY_CLASS_NAME,
        .dev_name = MEMORY_CLASS_NAME,
        .online = memory_subsys_online,
        .offline = memory_subsys_offline,
};

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 = to_memory_block(dev);

        kfree(mem);
}

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 = to_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 = to_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 = to_memory_block(dev);

        for (i = 0; i < sections_per_block; i++) {
                if (!present_section_nr(mem->start_section_nr + i))
                        continue;
                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 = to_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 ret = 0;

        if (mem->state != from_state_req)
                return -EINVAL;

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

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

        mem->state = ret ? from_state_req : to_state;

        return ret;
}

/* The device lock serializes operations on memory_subsys_[online|offline] */
static int memory_subsys_online(struct device *dev)
{
        struct memory_block *mem = to_memory_block(dev);
        int ret;

        if (mem->state == MEM_ONLINE)
                return 0;

        /*
         * If we are called from store_mem_state(), online_type will be
         * set >= 0 Otherwise we were called from the device online
         * attribute and need to set the online_type.
         */
        if (mem->online_type < 0)
                mem->online_type = ONLINE_KEEP;

        ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);

        /* clear online_type */
        mem->online_type = -1;

        return ret;
}

static int memory_subsys_offline(struct device *dev)
{
        struct memory_block *mem = to_memory_block(dev);

        if (mem->state == MEM_OFFLINE)
                return 0;

        return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
}

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

        ret = lock_device_hotplug_sysfs();
        if (ret)
                return ret;

        if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
                online_type = ONLINE_KERNEL;
        else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
                online_type = ONLINE_MOVABLE;
        else if (!strncmp(buf, "online", min_t(int, count, 6)))
                online_type = ONLINE_KEEP;
        else if (!strncmp(buf, "offline", min_t(int, count, 7)))
                online_type = -1;
        else {
                ret = -EINVAL;
                goto err;
        }

        switch (online_type) {
        case ONLINE_KERNEL:
        case ONLINE_MOVABLE:
        case ONLINE_KEEP:
                /*
                 * mem->online_type is not protected so there can be a
                 * race here.  However, when racing online, the first
                 * will succeed and the second will just return as the
                 * block will already be online.  The online type
                 * could be either one, but that is expected.
                 */
                mem->online_type = online_type;
                ret = device_online(&mem->dev);
                break;
        case -1:
                ret = device_offline(&mem->dev);
                break;
        default:
                ret = -EINVAL; /* should never happen */
        }

err:
        unlock_device_hotplug();

        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 = to_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);

/*
 * 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);

/*
 * 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);
#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 (kstrtoull(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 (kstrtoull(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);
#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 to_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 struct attribute *memory_memblk_attrs[] = {
        &dev_attr_phys_index.attr,
        &dev_attr_end_phys_index.attr,
        &dev_attr_state.attr,
        &dev_attr_phys_device.attr,
        &dev_attr_removable.attr,
        NULL
};

static struct attribute_group memory_memblk_attr_group = {
        .attrs = memory_memblk_attrs,
};

static const struct attribute_group *memory_memblk_attr_groups[] = {
        &memory_memblk_attr_group,
        NULL,
};

/*
 * register_memory - Setup a sysfs device for a memory block
 */
static
int register_memory(struct memory_block *memory)
{
        memory->dev.bus = &memory_subsys;
        memory->dev.id = memory->start_section_nr / sections_per_block;
        memory->dev.release = memory_block_release;
        memory->dev.groups = memory_memblk_attr_groups;
        memory->dev.offline = memory->state == MEM_OFFLINE;

        return device_register(&memory->dev);
}

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++;
        start_pfn = section_nr_to_pfn(mem->start_section_nr);
        mem->phys_device = arch_get_memory_phys_device(start_pfn);

        ret = register_memory(mem);

        *memory = mem;
        return ret;
}

static int add_memory_block(int base_section_nr)
{
        struct memory_block *mem;
        int i, ret, section_count = 0, section_nr;

        for (i = base_section_nr;
             (i < base_section_nr + sections_per_block) && i < NR_MEM_SECTIONS;
             i++) {
                if (!present_section_nr(i))
                        continue;
                if (section_count == 0)
                        section_nr = i;
                section_count++;
        }

        if (section_count == 0)
                return 0;
        ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE);
        if (ret)
                return ret;
        mem->section_count = section_count;
        return 0;
}


/*
 * 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)
{
        int ret = 0;
        struct memory_block *mem;

        mutex_lock(&mem_sysfs_mutex);

        mem = find_memory_block(section);
        if (mem) {
                mem->section_count++;
                put_device(&mem->dev);
        } else {
                ret = init_memory_block(&mem, section, MEM_OFFLINE);
                if (ret)
                        goto out;
        }

        if (mem->section_count == sections_per_block)
                ret = register_mem_sect_under_node(mem, nid);
out:
        mutex_unlock(&mem_sysfs_mutex);
        return ret;
}

#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() */
        put_device(&memory->dev);
        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)
                unregister_memory(mem);
        else
                put_device(&mem->dev);

        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 */

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

static struct attribute *memory_root_attrs[] = {
#ifdef CONFIG_ARCH_MEMORY_PROBE
        &dev_attr_probe.attr,
#endif

#ifdef CONFIG_MEMORY_FAILURE
        &dev_attr_soft_offline_page.attr,
        &dev_attr_hard_offline_page.attr,
#endif

        &dev_attr_block_size_bytes.attr,
        NULL
};

static struct attribute_group memory_root_attr_group = {
        .attrs = memory_root_attrs,
};

static const struct attribute_group *memory_root_attr_groups[] = {
        &memory_root_attr_group,
        NULL,
};

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

        ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
        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
         */
        mutex_lock(&mem_sysfs_mutex);
        for (i = 0; i < NR_MEM_SECTIONS; i += sections_per_block) {
                err = add_memory_block(i);
                if (!ret)
                        ret = err;
        }
        mutex_unlock(&mem_sysfs_mutex);

out:
        if (ret)
                printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
        return ret;
}