// SPDX-License-Identifier: GPL-2.0
/*
 * 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/stat.h>
#include <linux/slab.h>
#include <linux/xarray.h>
#include <linux/export.h>

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

#define MEMORY_CLASS_NAME       "memory"

static const char *const online_type_to_str[] = {
        [MMOP_OFFLINE] = "offline",
        [MMOP_ONLINE] = "online",
        [MMOP_ONLINE_KERNEL] = "online_kernel",
        [MMOP_ONLINE_MOVABLE] = "online_movable",
};

int mhp_online_type_from_str(const char *str)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(online_type_to_str); i++) {
                if (sysfs_streq(str, online_type_to_str[i]))
                        return i;
        }
        return -EINVAL;
}

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

int sections_per_block;
EXPORT_SYMBOL(sections_per_block);

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

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

/*
 * Memory blocks are cached in a local radix tree to avoid
 * a costly linear search for the corresponding device on
 * the subsystem bus.
 */
static DEFINE_XARRAY(memory_blocks);

/*
 * Memory groups, indexed by memory group id (mgid).
 */
static DEFINE_XARRAY_FLAGS(memory_groups, XA_FLAGS_ALLOC);
#define MEMORY_GROUP_MARK_DYNAMIC       XA_MARK_1

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 void memory_block_release(struct device *dev)
{
        struct memory_block *mem = to_memory_block(dev);
        /* Verify that the altmap is freed */
        WARN_ON(mem->altmap);
        kfree(mem);
}


/* Max block size to be set by memory_block_advise_max_size */
static unsigned long memory_block_advised_size;
static bool memory_block_advised_size_queried;

/**
 * memory_block_advise_max_size() - advise memory hotplug on the max suggested
 *                                  block size, usually for alignment.
 * @size: suggestion for maximum block size. must be aligned on power of 2.
 *
 * Early boot software (pre-allocator init) may advise archs on the max block
 * size. This value can only decrease after initialization, as the intent is
 * to identify the largest supported alignment for all sources.
 *
 * Use of this value is arch-defined, as is min/max block size.
 *
 * Return: 0 on success
 *         -EINVAL if size is 0 or not pow2 aligned
 *         -EBUSY if value has already been probed
 */
int __init memory_block_advise_max_size(unsigned long size)
{
        if (!size || !is_power_of_2(size))
                return -EINVAL;

        if (memory_block_advised_size_queried)
                return -EBUSY;

        if (memory_block_advised_size)
                memory_block_advised_size = min(memory_block_advised_size, size);
        else
                memory_block_advised_size = size;

        return 0;
}

/**
 * memory_block_advised_max_size() - query advised max hotplug block size.
 *
 * After the first call, the value can never change. Callers looking for the
 * actual block size should use memory_block_size_bytes. This interface is
 * intended for use by arch-init when initializing the hotplug block size.
 *
 * Return: advised size in bytes, or 0 if never set.
 */
unsigned long memory_block_advised_max_size(void)
{
        memory_block_advised_size_queried = true;
        return memory_block_advised_size;
}

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

/* Show the memory block ID, relative to the memory block size */
static ssize_t phys_index_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct memory_block *mem = to_memory_block(dev);

        return sysfs_emit(buf, "%08lx\n", memory_block_id(mem->start_section_nr));
}

/*
 * Legacy interface that we cannot remove. Always indicate "removable"
 * with CONFIG_MEMORY_HOTREMOVE - bad heuristic.
 */
static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        return sysfs_emit(buf, "%d\n", (int)IS_ENABLED(CONFIG_MEMORY_HOTREMOVE));
}

/*
 * online, offline, going offline, etc.
 */
static ssize_t state_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        struct memory_block *mem = to_memory_block(dev);
        const char *output;

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

        return sysfs_emit(buf, "%s\n", output);
}

int memory_notify(enum memory_block_state state, void *v)
{
        return blocking_notifier_call_chain(&memory_chain, state, v);
}

#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_MEMORY_HOTPLUG)
static unsigned long memblk_nr_poison(struct memory_block *mem);
#else
static inline unsigned long memblk_nr_poison(struct memory_block *mem)
{
        return 0;
}
#endif

/*
 * Must acquire mem_hotplug_lock in write mode.
 */
static int memory_block_online(struct memory_block *mem)
{
        unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
        unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
        unsigned long nr_vmemmap_pages = 0;
        struct zone *zone;
        int ret;

        if (memblk_nr_poison(mem))
                return -EHWPOISON;

        zone = zone_for_pfn_range(mem->online_type, mem->nid, mem->group,
                                  start_pfn, nr_pages);

        /*
         * Although vmemmap pages have a different lifecycle than the pages
         * they describe (they remain until the memory is unplugged), doing
         * their initialization and accounting at memory onlining/offlining
         * stage helps to keep accounting easier to follow - e.g vmemmaps
         * belong to the same zone as the memory they backed.
         */
        if (mem->altmap)
                nr_vmemmap_pages = mem->altmap->free;

        mem_hotplug_begin();
        if (nr_vmemmap_pages) {
                ret = mhp_init_memmap_on_memory(start_pfn, nr_vmemmap_pages, zone);
                if (ret)
                        goto out;
        }

        ret = online_pages(start_pfn + nr_vmemmap_pages,
                           nr_pages - nr_vmemmap_pages, zone, mem->group);
        if (ret) {
                if (nr_vmemmap_pages)
                        mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);
                goto out;
        }

        /*
         * Account once onlining succeeded. If the zone was unpopulated, it is
         * now already properly populated.
         */
        if (nr_vmemmap_pages)
                adjust_present_page_count(pfn_to_page(start_pfn), mem->group,
                                          nr_vmemmap_pages);

        mem->zone = zone;
out:
        mem_hotplug_done();
        return ret;
}

/*
 * Must acquire mem_hotplug_lock in write mode.
 */
static int memory_block_offline(struct memory_block *mem)
{
        unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
        unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
        unsigned long nr_vmemmap_pages = 0;
        int ret;

        if (!mem->zone)
                return -EINVAL;

        /*
         * Unaccount before offlining, such that unpopulated zone and kthreads
         * can properly be torn down in offline_pages().
         */
        if (mem->altmap)
                nr_vmemmap_pages = mem->altmap->free;

        mem_hotplug_begin();
        if (nr_vmemmap_pages)
                adjust_present_page_count(pfn_to_page(start_pfn), mem->group,
                                          -nr_vmemmap_pages);

        ret = offline_pages(start_pfn + nr_vmemmap_pages,
                            nr_pages - nr_vmemmap_pages, mem->zone, mem->group);
        if (ret) {
                /* offline_pages() failed. Account back. */
                if (nr_vmemmap_pages)
                        adjust_present_page_count(pfn_to_page(start_pfn),
                                                  mem->group, nr_vmemmap_pages);
                goto out;
        }

        if (nr_vmemmap_pages)
                mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);

        mem->zone = NULL;
out:
        mem_hotplug_done();
        return ret;
}

/*
 * 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(struct memory_block *mem, unsigned long action)
{
        int ret;

        switch (action) {
        case MEM_ONLINE:
                ret = memory_block_online(mem);
                break;
        case MEM_OFFLINE:
                ret = memory_block_offline(mem);
                break;
        default:
                WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
                     "%ld\n", __func__, mem->start_section_nr, 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, to_state);
        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;

        /*
         * When called via device_online() without configuring the online_type,
         * we want to default to MMOP_ONLINE.
         */
        if (mem->online_type == MMOP_OFFLINE)
                mem->online_type = MMOP_ONLINE;

        ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
        mem->online_type = MMOP_OFFLINE;

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

        if (online_type < 0)
                return -EINVAL;

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

        switch (online_type) {
        case MMOP_ONLINE_KERNEL:
        case MMOP_ONLINE_MOVABLE:
        case MMOP_ONLINE:
                /* mem->online_type is protected by device_hotplug_lock */
                mem->online_type = online_type;
                ret = device_online(&mem->dev);
                break;
        case MMOP_OFFLINE:
                ret = device_offline(&mem->dev);
                break;
        default:
                ret = -EINVAL; /* should never happen */
        }

        unlock_device_hotplug();

        if (ret < 0)
                return ret;
        if (ret)
                return -EINVAL;

        return count;
}

/*
 * Legacy interface that we cannot remove: s390x exposes the storage increment
 * covered by a memory block, allowing for identifying which memory blocks
 * comprise a storage increment. Since a memory block spans complete
 * storage increments nowadays, this interface is basically unused. Other
 * archs never exposed != 0.
 */
static ssize_t phys_device_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct memory_block *mem = to_memory_block(dev);
        unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);

        return sysfs_emit(buf, "%d\n",
                          arch_get_memory_phys_device(start_pfn));
}

#ifdef CONFIG_MEMORY_HOTREMOVE
static int print_allowed_zone(char *buf, int len, int nid,
                              struct memory_group *group,
                              unsigned long start_pfn, unsigned long nr_pages,
                              enum mmop online_type, struct zone *default_zone)
{
        struct zone *zone;

        zone = zone_for_pfn_range(online_type, nid, group, start_pfn, nr_pages);
        if (zone == default_zone)
                return 0;

        return sysfs_emit_at(buf, len, " %s", zone->name);
}

static ssize_t valid_zones_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct memory_block *mem = to_memory_block(dev);
        unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
        unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
        struct memory_group *group = mem->group;
        struct zone *default_zone;
        int nid = mem->nid;
        int len;

        /*
         * Check the existing zone. Make sure that we do that only on the
         * online nodes otherwise the page_zone is not reliable
         */
        if (mem->state == MEM_ONLINE) {
                /*
                 * If !mem->zone, the memory block spans multiple zones and
                 * cannot get offlined.
                 */
                return sysfs_emit(buf, "%s\n",
                                  mem->zone ? mem->zone->name : "none");
        }

        default_zone = zone_for_pfn_range(MMOP_ONLINE, nid, group,
                                          start_pfn, nr_pages);

        len = sysfs_emit(buf, "%s", default_zone->name);
        len += print_allowed_zone(buf, len, nid, group, start_pfn, nr_pages,
                                  MMOP_ONLINE_KERNEL, default_zone);
        len += print_allowed_zone(buf, len, nid, group, start_pfn, nr_pages,
                                  MMOP_ONLINE_MOVABLE, default_zone);
        len += sysfs_emit_at(buf, len, "\n");
        return len;
}
static DEVICE_ATTR_RO(valid_zones);
#endif

static DEVICE_ATTR_RO(phys_index);
static DEVICE_ATTR_RW(state);
static DEVICE_ATTR_RO(phys_device);
static DEVICE_ATTR_RO(removable);

/*
 * Show the memory block size (shared by all memory blocks).
 */
static ssize_t block_size_bytes_show(struct device *dev,
                                     struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", memory_block_size_bytes());
}

static DEVICE_ATTR_RO(block_size_bytes);

/*
 * Memory auto online policy.
 */

static ssize_t auto_online_blocks_show(struct device *dev,
                                       struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%s\n",
                          online_type_to_str[mhp_get_default_online_type()]);
}

static ssize_t auto_online_blocks_store(struct device *dev,
                                        struct device_attribute *attr,
                                        const char *buf, size_t count)
{
        const int online_type = mhp_online_type_from_str(buf);

        if (online_type < 0)
                return -EINVAL;

        mhp_set_default_online_type(online_type);
        return count;
}

static DEVICE_ATTR_RW(auto_online_blocks);

#ifdef CONFIG_CRASH_HOTPLUG
#include <linux/kexec.h>
static ssize_t crash_hotplug_show(struct device *dev,
                                       struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n", crash_check_hotplug_support());
}
static DEVICE_ATTR_RO(crash_hotplug);
#endif

/*
 * 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 probe_store(struct device *dev, struct device_attribute *attr,
                           const char *buf, size_t count)
{
        u64 phys_addr;
        int nid, ret;
        unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;

        ret = kstrtoull(buf, 0, &phys_addr);
        if (ret)
                return ret;

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

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

        nid = memory_add_physaddr_to_nid(phys_addr);
        ret = __add_memory(nid, phys_addr,
                           MIN_MEMORY_BLOCK_SIZE * sections_per_block,
                           MHP_NONE);

        if (ret)
                goto out;

        ret = count;
out:
        unlock_device_hotplug();
        return ret;
}

static DEVICE_ATTR_WO(probe);
#endif

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

/* Soft offline a page */
static ssize_t soft_offline_page_store(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 = soft_offline_page(pfn, 0);
        return ret == 0 ? count : ret;
}

/* Forcibly offline a page, including killing processes. */
static ssize_t hard_offline_page_store(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, MF_SW_SIMULATED);
        if (ret == -EOPNOTSUPP)
                ret = 0;
        return ret ? ret : count;
}

static DEVICE_ATTR_WO(soft_offline_page);
static DEVICE_ATTR_WO(hard_offline_page);
#endif

/* See phys_device_show(). */
int __weak arch_get_memory_phys_device(unsigned long start_pfn)
{
        return 0;
}

/*
 * A reference for the returned memory block device is acquired.
 *
 * Called under device_hotplug_lock.
 */
struct memory_block *memory_block_get(unsigned long block_id)
{
        struct memory_block *mem;

        mem = xa_load(&memory_blocks, block_id);
        if (mem)
                get_device(&mem->dev);
        return mem;
}

static struct attribute *memory_memblk_attrs[] = {
        &dev_attr_phys_index.attr,
        &dev_attr_state.attr,
        &dev_attr_phys_device.attr,
        &dev_attr_removable.attr,
#ifdef CONFIG_MEMORY_HOTREMOVE
        &dev_attr_valid_zones.attr,
#endif
        NULL
};

static const 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,
};

static int __add_memory_block(struct memory_block *memory)
{
        int ret;

        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;
        dev_assign_offline(&memory->dev, memory->state == MEM_OFFLINE);

        ret = device_register(&memory->dev);
        if (ret) {
                memory_block_put(memory);
                return ret;
        }
        ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
                              GFP_KERNEL));
        if (ret)
                device_unregister(&memory->dev);

        return ret;
}

static struct zone *early_node_zone_for_memory_block(struct memory_block *mem,
                                                     int nid)
{
        const unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
        const unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
        struct zone *zone, *matching_zone = NULL;
        pg_data_t *pgdat = NODE_DATA(nid);
        int i;

        /*
         * This logic only works for early memory, when the applicable zones
         * already span the memory block. We don't expect overlapping zones on
         * a single node for early memory. So if we're told that some PFNs
         * of a node fall into this memory block, we can assume that all node
         * zones that intersect with the memory block are actually applicable.
         * No need to look at the memmap.
         */
        for (i = 0; i < MAX_NR_ZONES; i++) {
                zone = pgdat->node_zones + i;
                if (!populated_zone(zone))
                        continue;
                if (!zone_intersects(zone, start_pfn, nr_pages))
                        continue;
                if (!matching_zone) {
                        matching_zone = zone;
                        continue;
                }
                /* Spans multiple zones ... */
                matching_zone = NULL;
                break;
        }
        return matching_zone;
}

#ifdef CONFIG_NUMA
/**
 * memory_block_add_nid_early() - Indicate that early system RAM falling into
 *                                this memory block device (partially) belongs
 *                                to the given node.
 * @mem: The memory block device.
 * @nid: The node id.
 *
 * Indicate that early system RAM falling into this memory block (partially)
 * belongs to the given node. This will also properly set/adjust mem->zone based
 * on the zone ranges of the given node.
 *
 * Memory hotplug handles this on memory block creation, where we can only have
 * a single nid span a memory block.
 */
void memory_block_add_nid_early(struct memory_block *mem, int nid)
{
        if (mem->nid != nid) {
                /*
                 * For early memory we have to determine the zone when setting
                 * the node id and handle multiple nodes spanning a single
                 * memory block by indicate via zone == NULL that we're not
                 * dealing with a single zone. So if we're setting the node id
                 * the first time, determine if there is a single zone. If we're
                 * setting the node id a second time to a different node,
                 * invalidate the single detected zone.
                 */
                if (mem->nid == NUMA_NO_NODE)
                        mem->zone = early_node_zone_for_memory_block(mem, nid);
                else
                        mem->zone = NULL;
                /*
                 * If this memory block spans multiple nodes, we only indicate
                 * the last processed node. If we span multiple nodes (not applicable
                 * to hotplugged memory), zone == NULL will prohibit memory offlining
                 * and consequently unplug.
                 */
                mem->nid = nid;
        }
}
#endif

static int add_memory_block(unsigned long block_id, int nid, unsigned long state,
                            struct vmem_altmap *altmap,
                            struct memory_group *group)
{
        struct memory_block *mem;
        int ret = 0;

        mem = memory_block_get(block_id);
        if (mem) {
                memory_block_put(mem);
                return -EEXIST;
        }
        mem = kzalloc_obj(*mem);
        if (!mem)
                return -ENOMEM;

        mem->start_section_nr = block_id * sections_per_block;
        mem->state = state;
        mem->nid = nid;
        INIT_LIST_HEAD(&mem->group_next);

#ifndef CONFIG_NUMA
        if (state == MEM_ONLINE)
                /*
                 * MEM_ONLINE at this point implies early memory. With NUMA,
                 * we'll determine the zone when setting the node id via
                 * memory_block_add_nid_early(). Memory hotplug updated the zone
                 * manually when memory onlining/offlining succeeds.
                 */
                mem->zone = early_node_zone_for_memory_block(mem, NUMA_NO_NODE);
#endif /* CONFIG_NUMA */

        ret = __add_memory_block(mem);
        if (ret)
                return ret;

        mem->altmap = altmap;

        if (group) {
                mem->group = group;
                list_add(&mem->group_next, &group->memory_blocks);
        }

        return 0;
}

static void remove_memory_block(struct memory_block *memory)
{
        if (WARN_ON_ONCE(memory->dev.bus != &memory_subsys))
                return;

        WARN_ON(xa_erase(&memory_blocks, memory->dev.id) == NULL);

        if (memory->group) {
                list_del(&memory->group_next);
                memory->group = NULL;
        }

        /* drop the ref. we got via memory_block_get() */
        memory_block_put(memory);
        device_unregister(&memory->dev);
}

/*
 * Create memory block devices for the given memory area. Start and size
 * have to be aligned to memory block granularity. Memory block devices
 * will be initialized as offline.
 *
 * Called under device_hotplug_lock.
 */
int create_memory_block_devices(unsigned long start, unsigned long size,
                                int nid, struct vmem_altmap *altmap,
                                struct memory_group *group)
{
        const unsigned long start_block_id = pfn_to_block_id(PFN_DOWN(start));
        unsigned long end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
        struct memory_block *mem;
        unsigned long block_id;
        int ret = 0;

        if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) ||
                         !IS_ALIGNED(size, memory_block_size_bytes())))
                return -EINVAL;

        for (block_id = start_block_id; block_id != end_block_id; block_id++) {
                ret = add_memory_block(block_id, nid, MEM_OFFLINE, altmap, group);
                if (ret)
                        break;
        }
        if (ret) {
                end_block_id = block_id;
                for (block_id = start_block_id; block_id != end_block_id;
                     block_id++) {
                        mem = memory_block_get(block_id);
                        if (WARN_ON_ONCE(!mem))
                                continue;
                        remove_memory_block(mem);
                }
        }
        return ret;
}

/*
 * Remove memory block devices for the given memory area. Start and size
 * have to be aligned to memory block granularity. Memory block devices
 * have to be offline.
 *
 * Called under device_hotplug_lock.
 */
void remove_memory_block_devices(unsigned long start, unsigned long size)
{
        const unsigned long start_block_id = pfn_to_block_id(PFN_DOWN(start));
        const unsigned long end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
        struct memory_block *mem;
        unsigned long block_id;

        if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) ||
                         !IS_ALIGNED(size, memory_block_size_bytes())))
                return;

        for (block_id = start_block_id; block_id != end_block_id; block_id++) {
                mem = memory_block_get(block_id);
                if (WARN_ON_ONCE(!mem))
                        continue;
                num_poisoned_pages_sub(-1UL, memblk_nr_poison(mem));
                unregister_memory_block_under_nodes(mem);
                remove_memory_block(mem);
        }
}

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,
        &dev_attr_auto_online_blocks.attr,
#ifdef CONFIG_CRASH_HOTPLUG
        &dev_attr_crash_hotplug.attr,
#endif
        NULL
};

static const 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. At the time this function
 * is called, we cannot have concurrent creation/deletion of memory block
 * devices, the device_hotplug_lock is not needed.
 */
void __init memory_dev_init(void)
{
        int ret;
        unsigned long block_sz, block_id, nr;

        /* Validate the configured memory block size */
        block_sz = memory_block_size_bytes();
        if (!is_power_of_2(block_sz) || block_sz < MIN_MEMORY_BLOCK_SIZE)
                panic("Memory block size not suitable: 0x%lx\n", block_sz);
        sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;

        ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
        if (ret)
                panic("%s() failed to register subsystem: %d\n", __func__, ret);

        /*
         * Create entries for memory sections that were found during boot
         * and have been initialized. Use @block_id to track the last
         * handled block and initialize it to an invalid value (ULONG_MAX)
         * to bypass the block ID matching check for the first present
         * block so that it can be covered.
         */
        block_id = ULONG_MAX;
        for_each_present_section_nr(0, nr) {
                if (block_id != ULONG_MAX && memory_block_id(nr) == block_id)
                        continue;

                block_id = memory_block_id(nr);
                ret = add_memory_block(block_id, NUMA_NO_NODE, MEM_ONLINE, NULL, NULL);
                if (ret) {
                        panic("%s() failed to add memory block: %d\n",
                              __func__, ret);
                }
        }
}

/**
 * walk_memory_blocks - walk through all present memory blocks overlapped
 *                      by the range [start, start + size)
 *
 * @start: start address of the memory range
 * @size: size of the memory range
 * @arg: argument passed to func
 * @func: callback for each memory section walked
 *
 * This function walks through all present memory blocks overlapped by the
 * range [start, start + size), calling func on each memory block.
 *
 * In case func() returns an error, walking is aborted and the error is
 * returned.
 *
 * Called under device_hotplug_lock.
 */
int walk_memory_blocks(unsigned long start, unsigned long size,
                       void *arg, walk_memory_blocks_func_t func)
{
        const unsigned long start_block_id = phys_to_block_id(start);
        const unsigned long end_block_id = phys_to_block_id(start + size - 1);
        struct memory_block *mem;
        unsigned long block_id;
        int ret = 0;

        if (!size)
                return 0;

        for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
                mem = memory_block_get(block_id);
                if (!mem)
                        continue;

                ret = func(mem, arg);
                memory_block_put(mem);
                if (ret)
                        break;
        }
        return ret;
}

struct for_each_memory_block_cb_data {
        walk_memory_blocks_func_t func;
        void *arg;
};

static int for_each_memory_block_cb(struct device *dev, void *data)
{
        struct memory_block *mem = to_memory_block(dev);
        struct for_each_memory_block_cb_data *cb_data = data;

        return cb_data->func(mem, cb_data->arg);
}

/**
 * for_each_memory_block - walk through all present memory blocks
 *
 * @arg: argument passed to func
 * @func: callback for each memory block walked
 *
 * This function walks through all present memory blocks, calling func on
 * each memory block.
 *
 * In case func() returns an error, walking is aborted and the error is
 * returned.
 */
int for_each_memory_block(void *arg, walk_memory_blocks_func_t func)
{
        struct for_each_memory_block_cb_data cb_data = {
                .func = func,
                .arg = arg,
        };

        return bus_for_each_dev(&memory_subsys, NULL, &cb_data,
                                for_each_memory_block_cb);
}

/*
 * This is an internal helper to unify allocation and initialization of
 * memory groups. Note that the passed memory group will be copied to a
 * dynamically allocated memory group. After this call, the passed
 * memory group should no longer be used.
 */
static int memory_group_register(struct memory_group group)
{
        struct memory_group *new_group;
        uint32_t mgid;
        int ret;

        if (!node_possible(group.nid))
                return -EINVAL;

        new_group = kzalloc_obj(group);
        if (!new_group)
                return -ENOMEM;
        *new_group = group;
        INIT_LIST_HEAD(&new_group->memory_blocks);

        ret = xa_alloc(&memory_groups, &mgid, new_group, xa_limit_31b,
                       GFP_KERNEL);
        if (ret) {
                kfree(new_group);
                return ret;
        } else if (group.is_dynamic) {
                xa_set_mark(&memory_groups, mgid, MEMORY_GROUP_MARK_DYNAMIC);
        }
        return mgid;
}

/**
 * memory_group_register_static() - Register a static memory group.
 * @nid: The node id.
 * @max_pages: The maximum number of pages we'll have in this static memory
 *             group.
 *
 * Register a new static memory group and return the memory group id.
 * All memory in the group belongs to a single unit, such as a DIMM. All
 * memory belonging to a static memory group is added in one go to be removed
 * in one go -- it's static.
 *
 * Returns an error if out of memory, if the node id is invalid, if no new
 * memory groups can be registered, or if max_pages is invalid (0). Otherwise,
 * returns the new memory group id.
 */
int memory_group_register_static(int nid, unsigned long max_pages)
{
        struct memory_group group = {
                .nid = nid,
                .s = {
                        .max_pages = max_pages,
                },
        };

        if (!max_pages)
                return -EINVAL;
        return memory_group_register(group);
}
EXPORT_SYMBOL_GPL(memory_group_register_static);

/**
 * memory_group_register_dynamic() - Register a dynamic memory group.
 * @nid: The node id.
 * @unit_pages: Unit in pages in which is memory added/removed in this dynamic
 *              memory group.
 *
 * Register a new dynamic memory group and return the memory group id.
 * Memory within a dynamic memory group is added/removed dynamically
 * in unit_pages.
 *
 * Returns an error if out of memory, if the node id is invalid, if no new
 * memory groups can be registered, or if unit_pages is invalid (0, not a
 * power of two, smaller than a single memory block). Otherwise, returns the
 * new memory group id.
 */
int memory_group_register_dynamic(int nid, unsigned long unit_pages)
{
        struct memory_group group = {
                .nid = nid,
                .is_dynamic = true,
                .d = {
                        .unit_pages = unit_pages,
                },
        };

        if (!unit_pages || !is_power_of_2(unit_pages) ||
            unit_pages < PHYS_PFN(memory_block_size_bytes()))
                return -EINVAL;
        return memory_group_register(group);
}
EXPORT_SYMBOL_GPL(memory_group_register_dynamic);

/**
 * memory_group_unregister() - Unregister a memory group.
 * @mgid: the memory group id
 *
 * Unregister a memory group. If any memory block still belongs to this
 * memory group, unregistering will fail.
 *
 * Returns -EINVAL if the memory group id is invalid, returns -EBUSY if some
 * memory blocks still belong to this memory group and returns 0 if
 * unregistering succeeded.
 */
int memory_group_unregister(int mgid)
{
        struct memory_group *group;

        if (mgid < 0)
                return -EINVAL;

        group = xa_load(&memory_groups, mgid);
        if (!group)
                return -EINVAL;
        if (!list_empty(&group->memory_blocks))
                return -EBUSY;
        xa_erase(&memory_groups, mgid);
        kfree(group);
        return 0;
}
EXPORT_SYMBOL_GPL(memory_group_unregister);

/*
 * This is an internal helper only to be used in core memory hotplug code to
 * lookup a memory group. We don't care about locking, as we don't expect a
 * memory group to get unregistered while adding memory to it -- because
 * the group and the memory is managed by the same driver.
 */
struct memory_group *memory_group_find_by_id(int mgid)
{
        return xa_load(&memory_groups, mgid);
}

/*
 * This is an internal helper only to be used in core memory hotplug code to
 * walk all dynamic memory groups excluding a given memory group, either
 * belonging to a specific node, or belonging to any node.
 */
int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
                               struct memory_group *excluded, void *arg)
{
        struct memory_group *group;
        unsigned long index;
        int ret = 0;

        xa_for_each_marked(&memory_groups, index, group,
                           MEMORY_GROUP_MARK_DYNAMIC) {
                if (group == excluded)
                        continue;
#ifdef CONFIG_NUMA
                if (nid != NUMA_NO_NODE && group->nid != nid)
                        continue;
#endif /* CONFIG_NUMA */
                ret = func(group, arg);
                if (ret)
                        break;
        }
        return ret;
}

#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_MEMORY_HOTPLUG)
void memblk_nr_poison_inc(unsigned long pfn)
{
        const unsigned long block_id = pfn_to_block_id(pfn);
        struct memory_block *mem = memory_block_get(block_id);

        if (mem) {
                atomic_long_inc(&mem->nr_hwpoison);
                memory_block_put(mem);
        }
}

void memblk_nr_poison_sub(unsigned long pfn, long i)
{
        const unsigned long block_id = pfn_to_block_id(pfn);
        struct memory_block *mem = memory_block_get(block_id);

        if (mem) {
                atomic_long_sub(i, &mem->nr_hwpoison);
                memory_block_put(mem);
        }
}

static unsigned long memblk_nr_poison(struct memory_block *mem)
{
        return atomic_long_read(&mem->nr_hwpoison);
}
#endif