memory.c

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/*
 * 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);

/*
 * 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;

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

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);
}

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,
                    unsigned long nr_pages)
{
    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)
{
    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, nr_pages))
                return -EBUSY;

            ret = online_pages(start_pfn, nr_pages);
            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) {
        ret = -EINVAL;
        goto out;
    }

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

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

    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 ret;

    mutex_lock(&mem->state_mutex);
    ret = __memory_block_change_state(mem, to_state, from_state_req);
    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", min((int)count, 6)))
        ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
    else if(!strncmp(buf, "offline", min((int)count, 7)))
        ret = memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);

    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, 0644, NULL, store_soft_offline_page);
static DEVICE_ATTR(hard_offline_page, 0644, 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;
}

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);
        kfree(mem);
    } else
        kobject_put(&mem->dev.kobj);

    mutex_unlock(&mem_sysfs_mutex);
    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)
{
    return add_memory_section(nid, section, NULL, MEM_OFFLINE, HOTPLUG);
}

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

    return remove_memory_block(0, section, 0);
}

/*
 * 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);
    mutex_unlock(&mem->state_mutex);

    return ret;
}

/*
 * 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;
}