// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic hugetlb support.
 * (C) Nadia Yvette Chambers, April 2004
 */
#include <linux/list.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/seq_file.h>
#include <linux/sysctl.h>
#include <linux/highmem.h>
#include <linux/mmu_notifier.h>
#include <linux/nodemask.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/compiler.h>
#include <linux/cpuset.h>
#include <linux/mutex.h>
#include <linux/memblock.h>
#include <linux/sysfs.h>
#include <linux/slab.h>
#include <linux/sched/mm.h>
#include <linux/mmdebug.h>
#include <linux/sched/signal.h>
#include <linux/rmap.h>
#include <linux/string_helpers.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/jhash.h>
#include <linux/numa.h>
#include <linux/llist.h>
#include <linux/cma.h>
#include <linux/migrate.h>

#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>

#include <linux/io.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/node.h>
#include <linux/page_owner.h>
#include "internal.h"
#include "hugetlb_vmemmap.h"

int hugetlb_max_hstate __read_mostly;
unsigned int default_hstate_idx;
struct hstate hstates[HUGE_MAX_HSTATE];

#ifdef CONFIG_CMA
static struct cma *hugetlb_cma[MAX_NUMNODES];
static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
static bool hugetlb_cma_page(struct page *page, unsigned int order)
{
        return cma_pages_valid(hugetlb_cma[page_to_nid(page)], page,
                                1 << order);
}
#else
static bool hugetlb_cma_page(struct page *page, unsigned int order)
{
        return false;
}
#endif
static unsigned long hugetlb_cma_size __initdata;

/*
 * Minimum page order among possible hugepage sizes, set to a proper value
 * at boot time.
 */
static unsigned int minimum_order __read_mostly = UINT_MAX;

__initdata LIST_HEAD(huge_boot_pages);

/* for command line parsing */
static struct hstate * __initdata parsed_hstate;
static unsigned long __initdata default_hstate_max_huge_pages;
static bool __initdata parsed_valid_hugepagesz = true;
static bool __initdata parsed_default_hugepagesz;
static unsigned int default_hugepages_in_node[MAX_NUMNODES] __initdata;

/*
 * Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
 * free_huge_pages, and surplus_huge_pages.
 */
DEFINE_SPINLOCK(hugetlb_lock);

/*
 * Serializes faults on the same logical page.  This is used to
 * prevent spurious OOMs when the hugepage pool is fully utilized.
 */
static int num_fault_mutexes;
struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;

/* Forward declaration */
static int hugetlb_acct_memory(struct hstate *h, long delta);

static inline bool subpool_is_free(struct hugepage_subpool *spool)
{
        if (spool->count)
                return false;
        if (spool->max_hpages != -1)
                return spool->used_hpages == 0;
        if (spool->min_hpages != -1)
                return spool->rsv_hpages == spool->min_hpages;

        return true;
}

static inline void unlock_or_release_subpool(struct hugepage_subpool *spool,
                                                unsigned long irq_flags)
{
        spin_unlock_irqrestore(&spool->lock, irq_flags);

        /* If no pages are used, and no other handles to the subpool
         * remain, give up any reservations based on minimum size and
         * free the subpool */
        if (subpool_is_free(spool)) {
                if (spool->min_hpages != -1)
                        hugetlb_acct_memory(spool->hstate,
                                                -spool->min_hpages);
                kfree(spool);
        }
}

struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages,
                                                long min_hpages)
{
        struct hugepage_subpool *spool;

        spool = kzalloc(sizeof(*spool), GFP_KERNEL);
        if (!spool)
                return NULL;

        spin_lock_init(&spool->lock);
        spool->count = 1;
        spool->max_hpages = max_hpages;
        spool->hstate = h;
        spool->min_hpages = min_hpages;

        if (min_hpages != -1 && hugetlb_acct_memory(h, min_hpages)) {
                kfree(spool);
                return NULL;
        }
        spool->rsv_hpages = min_hpages;

        return spool;
}

void hugepage_put_subpool(struct hugepage_subpool *spool)
{
        unsigned long flags;

        spin_lock_irqsave(&spool->lock, flags);
        BUG_ON(!spool->count);
        spool->count--;
        unlock_or_release_subpool(spool, flags);
}

/*
 * Subpool accounting for allocating and reserving pages.
 * Return -ENOMEM if there are not enough resources to satisfy the
 * request.  Otherwise, return the number of pages by which the
 * global pools must be adjusted (upward).  The returned value may
 * only be different than the passed value (delta) in the case where
 * a subpool minimum size must be maintained.
 */
static long hugepage_subpool_get_pages(struct hugepage_subpool *spool,
                                      long delta)
{
        long ret = delta;

        if (!spool)
                return ret;

        spin_lock_irq(&spool->lock);

        if (spool->max_hpages != -1) {          /* maximum size accounting */
                if ((spool->used_hpages + delta) <= spool->max_hpages)
                        spool->used_hpages += delta;
                else {
                        ret = -ENOMEM;
                        goto unlock_ret;
                }
        }

        /* minimum size accounting */
        if (spool->min_hpages != -1 && spool->rsv_hpages) {
                if (delta > spool->rsv_hpages) {
                        /*
                         * Asking for more reserves than those already taken on
                         * behalf of subpool.  Return difference.
                         */
                        ret = delta - spool->rsv_hpages;
                        spool->rsv_hpages = 0;
                } else {
                        ret = 0;        /* reserves already accounted for */
                        spool->rsv_hpages -= delta;
                }
        }

unlock_ret:
        spin_unlock_irq(&spool->lock);
        return ret;
}

/*
 * Subpool accounting for freeing and unreserving pages.
 * Return the number of global page reservations that must be dropped.
 * The return value may only be different than the passed value (delta)
 * in the case where a subpool minimum size must be maintained.
 */
static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
                                       long delta)
{
        long ret = delta;
        unsigned long flags;

        if (!spool)
                return delta;

        spin_lock_irqsave(&spool->lock, flags);

        if (spool->max_hpages != -1)            /* maximum size accounting */
                spool->used_hpages -= delta;

         /* minimum size accounting */
        if (spool->min_hpages != -1 && spool->used_hpages < spool->min_hpages) {
                if (spool->rsv_hpages + delta <= spool->min_hpages)
                        ret = 0;
                else
                        ret = spool->rsv_hpages + delta - spool->min_hpages;

                spool->rsv_hpages += delta;
                if (spool->rsv_hpages > spool->min_hpages)
                        spool->rsv_hpages = spool->min_hpages;
        }

        /*
         * If hugetlbfs_put_super couldn't free spool due to an outstanding
         * quota reference, free it now.
         */
        unlock_or_release_subpool(spool, flags);

        return ret;
}

static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
{
        return HUGETLBFS_SB(inode->i_sb)->spool;
}

static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
{
        return subpool_inode(file_inode(vma->vm_file));
}

/* Helper that removes a struct file_region from the resv_map cache and returns
 * it for use.
 */
static struct file_region *
get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
{
        struct file_region *nrg = NULL;

        VM_BUG_ON(resv->region_cache_count <= 0);

        resv->region_cache_count--;
        nrg = list_first_entry(&resv->region_cache, struct file_region, link);
        list_del(&nrg->link);

        nrg->from = from;
        nrg->to = to;

        return nrg;
}

static void copy_hugetlb_cgroup_uncharge_info(struct file_region *nrg,
                                              struct file_region *rg)
{
#ifdef CONFIG_CGROUP_HUGETLB
        nrg->reservation_counter = rg->reservation_counter;
        nrg->css = rg->css;
        if (rg->css)
                css_get(rg->css);
#endif
}

/* Helper that records hugetlb_cgroup uncharge info. */
static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup *h_cg,
                                                struct hstate *h,
                                                struct resv_map *resv,
                                                struct file_region *nrg)
{
#ifdef CONFIG_CGROUP_HUGETLB
        if (h_cg) {
                nrg->reservation_counter =
                        &h_cg->rsvd_hugepage[hstate_index(h)];
                nrg->css = &h_cg->css;
                /*
                 * The caller will hold exactly one h_cg->css reference for the
                 * whole contiguous reservation region. But this area might be
                 * scattered when there are already some file_regions reside in
                 * it. As a result, many file_regions may share only one css
                 * reference. In order to ensure that one file_region must hold
                 * exactly one h_cg->css reference, we should do css_get for
                 * each file_region and leave the reference held by caller
                 * untouched.
                 */
                css_get(&h_cg->css);
                if (!resv->pages_per_hpage)
                        resv->pages_per_hpage = pages_per_huge_page(h);
                /* pages_per_hpage should be the same for all entries in
                 * a resv_map.
                 */
                VM_BUG_ON(resv->pages_per_hpage != pages_per_huge_page(h));
        } else {
                nrg->reservation_counter = NULL;
                nrg->css = NULL;
        }
#endif
}

static void put_uncharge_info(struct file_region *rg)
{
#ifdef CONFIG_CGROUP_HUGETLB
        if (rg->css)
                css_put(rg->css);
#endif
}

static bool has_same_uncharge_info(struct file_region *rg,
                                   struct file_region *org)
{
#ifdef CONFIG_CGROUP_HUGETLB
        return rg->reservation_counter == org->reservation_counter &&
               rg->css == org->css;

#else
        return true;
#endif
}

static void coalesce_file_region(struct resv_map *resv, struct file_region *rg)
{
        struct file_region *nrg = NULL, *prg = NULL;

        prg = list_prev_entry(rg, link);
        if (&prg->link != &resv->regions && prg->to == rg->from &&
            has_same_uncharge_info(prg, rg)) {
                prg->to = rg->to;

                list_del(&rg->link);
                put_uncharge_info(rg);
                kfree(rg);

                rg = prg;
        }

        nrg = list_next_entry(rg, link);
        if (&nrg->link != &resv->regions && nrg->from == rg->to &&
            has_same_uncharge_info(nrg, rg)) {
                nrg->from = rg->from;

                list_del(&rg->link);
                put_uncharge_info(rg);
                kfree(rg);
        }
}

static inline long
hugetlb_resv_map_add(struct resv_map *map, struct file_region *rg, long from,
                     long to, struct hstate *h, struct hugetlb_cgroup *cg,
                     long *regions_needed)
{
        struct file_region *nrg;

        if (!regions_needed) {
                nrg = get_file_region_entry_from_cache(map, from, to);
                record_hugetlb_cgroup_uncharge_info(cg, h, map, nrg);
                list_add(&nrg->link, rg->link.prev);
                coalesce_file_region(map, nrg);
        } else
                *regions_needed += 1;

        return to - from;
}

/*
 * Must be called with resv->lock held.
 *
 * Calling this with regions_needed != NULL will count the number of pages
 * to be added but will not modify the linked list. And regions_needed will
 * indicate the number of file_regions needed in the cache to carry out to add
 * the regions for this range.
 */
static long add_reservation_in_range(struct resv_map *resv, long f, long t,
                                     struct hugetlb_cgroup *h_cg,
                                     struct hstate *h, long *regions_needed)
{
        long add = 0;
        struct list_head *head = &resv->regions;
        long last_accounted_offset = f;
        struct file_region *rg = NULL, *trg = NULL;

        if (regions_needed)
                *regions_needed = 0;

        /* In this loop, we essentially handle an entry for the range
         * [last_accounted_offset, rg->from), at every iteration, with some
         * bounds checking.
         */
        list_for_each_entry_safe(rg, trg, head, link) {
                /* Skip irrelevant regions that start before our range. */
                if (rg->from < f) {
                        /* If this region ends after the last accounted offset,
                         * then we need to update last_accounted_offset.
                         */
                        if (rg->to > last_accounted_offset)
                                last_accounted_offset = rg->to;
                        continue;
                }

                /* When we find a region that starts beyond our range, we've
                 * finished.
                 */
                if (rg->from >= t)
                        break;

                /* Add an entry for last_accounted_offset -> rg->from, and
                 * update last_accounted_offset.
                 */
                if (rg->from > last_accounted_offset)
                        add += hugetlb_resv_map_add(resv, rg,
                                                    last_accounted_offset,
                                                    rg->from, h, h_cg,
                                                    regions_needed);

                last_accounted_offset = rg->to;
        }

        /* Handle the case where our range extends beyond
         * last_accounted_offset.
         */
        if (last_accounted_offset < t)
                add += hugetlb_resv_map_add(resv, rg, last_accounted_offset,
                                            t, h, h_cg, regions_needed);

        return add;
}

/* Must be called with resv->lock acquired. Will drop lock to allocate entries.
 */
static int allocate_file_region_entries(struct resv_map *resv,
                                        int regions_needed)
        __must_hold(&resv->lock)
{
        struct list_head allocated_regions;
        int to_allocate = 0, i = 0;
        struct file_region *trg = NULL, *rg = NULL;

        VM_BUG_ON(regions_needed < 0);

        INIT_LIST_HEAD(&allocated_regions);

        /*
         * Check for sufficient descriptors in the cache to accommodate
         * the number of in progress add operations plus regions_needed.
         *
         * This is a while loop because when we drop the lock, some other call
         * to region_add or region_del may have consumed some region_entries,
         * so we keep looping here until we finally have enough entries for
         * (adds_in_progress + regions_needed).
         */
        while (resv->region_cache_count <
               (resv->adds_in_progress + regions_needed)) {
                to_allocate = resv->adds_in_progress + regions_needed -
                              resv->region_cache_count;

                /* At this point, we should have enough entries in the cache
                 * for all the existing adds_in_progress. We should only be
                 * needing to allocate for regions_needed.
                 */
                VM_BUG_ON(resv->region_cache_count < resv->adds_in_progress);

                spin_unlock(&resv->lock);
                for (i = 0; i < to_allocate; i++) {
                        trg = kmalloc(sizeof(*trg), GFP_KERNEL);
                        if (!trg)
                                goto out_of_memory;
                        list_add(&trg->link, &allocated_regions);
                }

                spin_lock(&resv->lock);

                list_splice(&allocated_regions, &resv->region_cache);
                resv->region_cache_count += to_allocate;
        }

        return 0;

out_of_memory:
        list_for_each_entry_safe(rg, trg, &allocated_regions, link) {
                list_del(&rg->link);
                kfree(rg);
        }
        return -ENOMEM;
}

/*
 * Add the huge page range represented by [f, t) to the reserve
 * map.  Regions will be taken from the cache to fill in this range.
 * Sufficient regions should exist in the cache due to the previous
 * call to region_chg with the same range, but in some cases the cache will not
 * have sufficient entries due to races with other code doing region_add or
 * region_del.  The extra needed entries will be allocated.
 *
 * regions_needed is the out value provided by a previous call to region_chg.
 *
 * Return the number of new huge pages added to the map.  This number is greater
 * than or equal to zero.  If file_region entries needed to be allocated for
 * this operation and we were not able to allocate, it returns -ENOMEM.
 * region_add of regions of length 1 never allocate file_regions and cannot
 * fail; region_chg will always allocate at least 1 entry and a region_add for
 * 1 page will only require at most 1 entry.
 */
static long region_add(struct resv_map *resv, long f, long t,
                       long in_regions_needed, struct hstate *h,
                       struct hugetlb_cgroup *h_cg)
{
        long add = 0, actual_regions_needed = 0;

        spin_lock(&resv->lock);
retry:

        /* Count how many regions are actually needed to execute this add. */
        add_reservation_in_range(resv, f, t, NULL, NULL,
                                 &actual_regions_needed);

        /*
         * Check for sufficient descriptors in the cache to accommodate
         * this add operation. Note that actual_regions_needed may be greater
         * than in_regions_needed, as the resv_map may have been modified since
         * the region_chg call. In this case, we need to make sure that we
         * allocate extra entries, such that we have enough for all the
         * existing adds_in_progress, plus the excess needed for this
         * operation.
         */
        if (actual_regions_needed > in_regions_needed &&
            resv->region_cache_count <
                    resv->adds_in_progress +
                            (actual_regions_needed - in_regions_needed)) {
                /* region_add operation of range 1 should never need to
                 * allocate file_region entries.
                 */
                VM_BUG_ON(t - f <= 1);

                if (allocate_file_region_entries(
                            resv, actual_regions_needed - in_regions_needed)) {
                        return -ENOMEM;
                }

                goto retry;
        }

        add = add_reservation_in_range(resv, f, t, h_cg, h, NULL);

        resv->adds_in_progress -= in_regions_needed;

        spin_unlock(&resv->lock);
        return add;
}

/*
 * Examine the existing reserve map and determine how many
 * huge pages in the specified range [f, t) are NOT currently
 * represented.  This routine is called before a subsequent
 * call to region_add that will actually modify the reserve
 * map to add the specified range [f, t).  region_chg does
 * not change the number of huge pages represented by the
 * map.  A number of new file_region structures is added to the cache as a
 * placeholder, for the subsequent region_add call to use. At least 1
 * file_region structure is added.
 *
 * out_regions_needed is the number of regions added to the
 * resv->adds_in_progress.  This value needs to be provided to a follow up call
 * to region_add or region_abort for proper accounting.
 *
 * Returns the number of huge pages that need to be added to the existing
 * reservation map for the range [f, t).  This number is greater or equal to
 * zero.  -ENOMEM is returned if a new file_region structure or cache entry
 * is needed and can not be allocated.
 */
static long region_chg(struct resv_map *resv, long f, long t,
                       long *out_regions_needed)
{
        long chg = 0;

        spin_lock(&resv->lock);

        /* Count how many hugepages in this range are NOT represented. */
        chg = add_reservation_in_range(resv, f, t, NULL, NULL,
                                       out_regions_needed);

        if (*out_regions_needed == 0)
                *out_regions_needed = 1;

        if (allocate_file_region_entries(resv, *out_regions_needed))
                return -ENOMEM;

        resv->adds_in_progress += *out_regions_needed;

        spin_unlock(&resv->lock);
        return chg;
}

/*
 * Abort the in progress add operation.  The adds_in_progress field
 * of the resv_map keeps track of the operations in progress between
 * calls to region_chg and region_add.  Operations are sometimes
 * aborted after the call to region_chg.  In such cases, region_abort
 * is called to decrement the adds_in_progress counter. regions_needed
 * is the value returned by the region_chg call, it is used to decrement
 * the adds_in_progress counter.
 *
 * NOTE: The range arguments [f, t) are not needed or used in this
 * routine.  They are kept to make reading the calling code easier as
 * arguments will match the associated region_chg call.
 */
static void region_abort(struct resv_map *resv, long f, long t,
                         long regions_needed)
{
        spin_lock(&resv->lock);
        VM_BUG_ON(!resv->region_cache_count);
        resv->adds_in_progress -= regions_needed;
        spin_unlock(&resv->lock);
}

/*
 * Delete the specified range [f, t) from the reserve map.  If the
 * t parameter is LONG_MAX, this indicates that ALL regions after f
 * should be deleted.  Locate the regions which intersect [f, t)
 * and either trim, delete or split the existing regions.
 *
 * Returns the number of huge pages deleted from the reserve map.
 * In the normal case, the return value is zero or more.  In the
 * case where a region must be split, a new region descriptor must
 * be allocated.  If the allocation fails, -ENOMEM will be returned.
 * NOTE: If the parameter t == LONG_MAX, then we will never split
 * a region and possibly return -ENOMEM.  Callers specifying
 * t == LONG_MAX do not need to check for -ENOMEM error.
 */
static long region_del(struct resv_map *resv, long f, long t)
{
        struct list_head *head = &resv->regions;
        struct file_region *rg, *trg;
        struct file_region *nrg = NULL;
        long del = 0;

retry:
        spin_lock(&resv->lock);
        list_for_each_entry_safe(rg, trg, head, link) {
                /*
                 * Skip regions before the range to be deleted.  file_region
                 * ranges are normally of the form [from, to).  However, there
                 * may be a "placeholder" entry in the map which is of the form
                 * (from, to) with from == to.  Check for placeholder entries
                 * at the beginning of the range to be deleted.
                 */
                if (rg->to <= f && (rg->to != rg->from || rg->to != f))
                        continue;

                if (rg->from >= t)
                        break;

                if (f > rg->from && t < rg->to) { /* Must split region */
                        /*
                         * Check for an entry in the cache before dropping
                         * lock and attempting allocation.
                         */
                        if (!nrg &&
                            resv->region_cache_count > resv->adds_in_progress) {
                                nrg = list_first_entry(&resv->region_cache,
                                                        struct file_region,
                                                        link);
                                list_del(&nrg->link);
                                resv->region_cache_count--;
                        }

                        if (!nrg) {
                                spin_unlock(&resv->lock);
                                nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
                                if (!nrg)
                                        return -ENOMEM;
                                goto retry;
                        }

                        del += t - f;
                        hugetlb_cgroup_uncharge_file_region(
                                resv, rg, t - f, false);

                        /* New entry for end of split region */
                        nrg->from = t;
                        nrg->to = rg->to;

                        copy_hugetlb_cgroup_uncharge_info(nrg, rg);

                        INIT_LIST_HEAD(&nrg->link);

                        /* Original entry is trimmed */
                        rg->to = f;

                        list_add(&nrg->link, &rg->link);
                        nrg = NULL;
                        break;
                }

                if (f <= rg->from && t >= rg->to) { /* Remove entire region */
                        del += rg->to - rg->from;
                        hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                            rg->to - rg->from, true);
                        list_del(&rg->link);
                        kfree(rg);
                        continue;
                }

                if (f <= rg->from) {    /* Trim beginning of region */
                        hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                            t - rg->from, false);

                        del += t - rg->from;
                        rg->from = t;
                } else {                /* Trim end of region */
                        hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                            rg->to - f, false);

                        del += rg->to - f;
                        rg->to = f;
                }
        }

        spin_unlock(&resv->lock);
        kfree(nrg);
        return del;
}

/*
 * A rare out of memory error was encountered which prevented removal of
 * the reserve map region for a page.  The huge page itself was free'ed
 * and removed from the page cache.  This routine will adjust the subpool
 * usage count, and the global reserve count if needed.  By incrementing
 * these counts, the reserve map entry which could not be deleted will
 * appear as a "reserved" entry instead of simply dangling with incorrect
 * counts.
 */
void hugetlb_fix_reserve_counts(struct inode *inode)
{
        struct hugepage_subpool *spool = subpool_inode(inode);
        long rsv_adjust;
        bool reserved = false;

        rsv_adjust = hugepage_subpool_get_pages(spool, 1);
        if (rsv_adjust > 0) {
                struct hstate *h = hstate_inode(inode);

                if (!hugetlb_acct_memory(h, 1))
                        reserved = true;
        } else if (!rsv_adjust) {
                reserved = true;
        }

        if (!reserved)
                pr_warn("hugetlb: Huge Page Reserved count may go negative.\n");
}

/*
 * Count and return the number of huge pages in the reserve map
 * that intersect with the range [f, t).
 */
static long region_count(struct resv_map *resv, long f, long t)
{
        struct list_head *head = &resv->regions;
        struct file_region *rg;
        long chg = 0;

        spin_lock(&resv->lock);
        /* Locate each segment we overlap with, and count that overlap. */
        list_for_each_entry(rg, head, link) {
                long seg_from;
                long seg_to;

                if (rg->to <= f)
                        continue;
                if (rg->from >= t)
                        break;

                seg_from = max(rg->from, f);
                seg_to = min(rg->to, t);

                chg += seg_to - seg_from;
        }
        spin_unlock(&resv->lock);

        return chg;
}

/*
 * Convert the address within this vma to the page offset within
 * the mapping, in pagecache page units; huge pages here.
 */
static pgoff_t vma_hugecache_offset(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long address)
{
        return ((address - vma->vm_start) >> huge_page_shift(h)) +
                        (vma->vm_pgoff >> huge_page_order(h));
}

pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
                                     unsigned long address)
{
        return vma_hugecache_offset(hstate_vma(vma), vma, address);
}
EXPORT_SYMBOL_GPL(linear_hugepage_index);

/*
 * Return the size of the pages allocated when backing a VMA. In the majority
 * cases this will be same size as used by the page table entries.
 */
unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
{
        if (vma->vm_ops && vma->vm_ops->pagesize)
                return vma->vm_ops->pagesize(vma);
        return PAGE_SIZE;
}
EXPORT_SYMBOL_GPL(vma_kernel_pagesize);

/*
 * Return the page size being used by the MMU to back a VMA. In the majority
 * of cases, the page size used by the kernel matches the MMU size. On
 * architectures where it differs, an architecture-specific 'strong'
 * version of this symbol is required.
 */
__weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
{
        return vma_kernel_pagesize(vma);
}

/*
 * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
 * bits of the reservation map pointer, which are always clear due to
 * alignment.
 */
#define HPAGE_RESV_OWNER    (1UL << 0)
#define HPAGE_RESV_UNMAPPED (1UL << 1)
#define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)

/*
 * These helpers are used to track how many pages are reserved for
 * faults in a MAP_PRIVATE mapping. Only the process that called mmap()
 * is guaranteed to have their future faults succeed.
 *
 * With the exception of reset_vma_resv_huge_pages() which is called at fork(),
 * the reserve counters are updated with the hugetlb_lock held. It is safe
 * to reset the VMA at fork() time as it is not in use yet and there is no
 * chance of the global counters getting corrupted as a result of the values.
 *
 * The private mapping reservation is represented in a subtly different
 * manner to a shared mapping.  A shared mapping has a region map associated
 * with the underlying file, this region map represents the backing file
 * pages which have ever had a reservation assigned which this persists even
 * after the page is instantiated.  A private mapping has a region map
 * associated with the original mmap which is attached to all VMAs which
 * reference it, this region map represents those offsets which have consumed
 * reservation ie. where pages have been instantiated.
 */
static unsigned long get_vma_private_data(struct vm_area_struct *vma)
{
        return (unsigned long)vma->vm_private_data;
}

static void set_vma_private_data(struct vm_area_struct *vma,
                                                        unsigned long value)
{
        vma->vm_private_data = (void *)value;
}

static void
resv_map_set_hugetlb_cgroup_uncharge_info(struct resv_map *resv_map,
                                          struct hugetlb_cgroup *h_cg,
                                          struct hstate *h)
{
#ifdef CONFIG_CGROUP_HUGETLB
        if (!h_cg || !h) {
                resv_map->reservation_counter = NULL;
                resv_map->pages_per_hpage = 0;
                resv_map->css = NULL;
        } else {
                resv_map->reservation_counter =
                        &h_cg->rsvd_hugepage[hstate_index(h)];
                resv_map->pages_per_hpage = pages_per_huge_page(h);
                resv_map->css = &h_cg->css;
        }
#endif
}

struct resv_map *resv_map_alloc(void)
{
        struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
        struct file_region *rg = kmalloc(sizeof(*rg), GFP_KERNEL);

        if (!resv_map || !rg) {
                kfree(resv_map);
                kfree(rg);
                return NULL;
        }

        kref_init(&resv_map->refs);
        spin_lock_init(&resv_map->lock);
        INIT_LIST_HEAD(&resv_map->regions);

        resv_map->adds_in_progress = 0;
        /*
         * Initialize these to 0. On shared mappings, 0's here indicate these
         * fields don't do cgroup accounting. On private mappings, these will be
         * re-initialized to the proper values, to indicate that hugetlb cgroup
         * reservations are to be un-charged from here.
         */
        resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, NULL, NULL);

        INIT_LIST_HEAD(&resv_map->region_cache);
        list_add(&rg->link, &resv_map->region_cache);
        resv_map->region_cache_count = 1;

        return resv_map;
}

void resv_map_release(struct kref *ref)
{
        struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
        struct list_head *head = &resv_map->region_cache;
        struct file_region *rg, *trg;

        /* Clear out any active regions before we release the map. */
        region_del(resv_map, 0, LONG_MAX);

        /* ... and any entries left in the cache */
        list_for_each_entry_safe(rg, trg, head, link) {
                list_del(&rg->link);
                kfree(rg);
        }

        VM_BUG_ON(resv_map->adds_in_progress);

        kfree(resv_map);
}

static inline struct resv_map *inode_resv_map(struct inode *inode)
{
        /*
         * At inode evict time, i_mapping may not point to the original
         * address space within the inode.  This original address space
         * contains the pointer to the resv_map.  So, always use the
         * address space embedded within the inode.
         * The VERY common case is inode->mapping == &inode->i_data but,
         * this may not be true for device special inodes.
         */
        return (struct resv_map *)(&inode->i_data)->private_data;
}

static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
{
        VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
        if (vma->vm_flags & VM_MAYSHARE) {
                struct address_space *mapping = vma->vm_file->f_mapping;
                struct inode *inode = mapping->host;

                return inode_resv_map(inode);

        } else {
                return (struct resv_map *)(get_vma_private_data(vma) &
                                                        ~HPAGE_RESV_MASK);
        }
}

static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
{
        VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
        VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);

        set_vma_private_data(vma, (get_vma_private_data(vma) &
                                HPAGE_RESV_MASK) | (unsigned long)map);
}

static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
{
        VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
        VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);

        set_vma_private_data(vma, get_vma_private_data(vma) | flags);
}

static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
{
        VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);

        return (get_vma_private_data(vma) & flag) != 0;
}

/* Reset counters to 0 and clear all HPAGE_RESV_* flags */
void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
{
        VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
        if (!(vma->vm_flags & VM_MAYSHARE))
                vma->vm_private_data = (void *)0;
}

/*
 * Reset and decrement one ref on hugepage private reservation.
 * Called with mm->mmap_sem writer semaphore held.
 * This function should be only used by move_vma() and operate on
 * same sized vma. It should never come here with last ref on the
 * reservation.
 */
void clear_vma_resv_huge_pages(struct vm_area_struct *vma)
{
        /*
         * Clear the old hugetlb private page reservation.
         * It has already been transferred to new_vma.
         *
         * During a mremap() operation of a hugetlb vma we call move_vma()
         * which copies vma into new_vma and unmaps vma. After the copy
         * operation both new_vma and vma share a reference to the resv_map
         * struct, and at that point vma is about to be unmapped. We don't
         * want to return the reservation to the pool at unmap of vma because
         * the reservation still lives on in new_vma, so simply decrement the
         * ref here and remove the resv_map reference from this vma.
         */
        struct resv_map *reservations = vma_resv_map(vma);

        if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                resv_map_put_hugetlb_cgroup_uncharge_info(reservations);
                kref_put(&reservations->refs, resv_map_release);
        }

        reset_vma_resv_huge_pages(vma);
}

/* Returns true if the VMA has associated reserve pages */
static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
{
        if (vma->vm_flags & VM_NORESERVE) {
                /*
                 * This address is already reserved by other process(chg == 0),
                 * so, we should decrement reserved count. Without decrementing,
                 * reserve count remains after releasing inode, because this
                 * allocated page will go into page cache and is regarded as
                 * coming from reserved pool in releasing step.  Currently, we
                 * don't have any other solution to deal with this situation
                 * properly, so add work-around here.
                 */
                if (vma->vm_flags & VM_MAYSHARE && chg == 0)
                        return true;
                else
                        return false;
        }

        /* Shared mappings always use reserves */
        if (vma->vm_flags & VM_MAYSHARE) {
                /*
                 * We know VM_NORESERVE is not set.  Therefore, there SHOULD
                 * be a region map for all pages.  The only situation where
                 * there is no region map is if a hole was punched via
                 * fallocate.  In this case, there really are no reserves to
                 * use.  This situation is indicated if chg != 0.
                 */
                if (chg)
                        return false;
                else
                        return true;
        }

        /*
         * Only the process that called mmap() has reserves for
         * private mappings.
         */
        if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                /*
                 * Like the shared case above, a hole punch or truncate
                 * could have been performed on the private mapping.
                 * Examine the value of chg to determine if reserves
                 * actually exist or were previously consumed.
                 * Very Subtle - The value of chg comes from a previous
                 * call to vma_needs_reserves().  The reserve map for
                 * private mappings has different (opposite) semantics
                 * than that of shared mappings.  vma_needs_reserves()
                 * has already taken this difference in semantics into
                 * account.  Therefore, the meaning of chg is the same
                 * as in the shared case above.  Code could easily be
                 * combined, but keeping it separate draws attention to
                 * subtle differences.
                 */
                if (chg)
                        return false;
                else
                        return true;
        }

        return false;
}

static void enqueue_huge_page(struct hstate *h, struct page *page)
{
        int nid = page_to_nid(page);

        lockdep_assert_held(&hugetlb_lock);
        VM_BUG_ON_PAGE(page_count(page), page);

        list_move(&page->lru, &h->hugepage_freelists[nid]);
        h->free_huge_pages++;
        h->free_huge_pages_node[nid]++;
        SetHPageFreed(page);
}

static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
{
        struct page *page;
        bool pin = !!(current->flags & PF_MEMALLOC_PIN);

        lockdep_assert_held(&hugetlb_lock);
        list_for_each_entry(page, &h->hugepage_freelists[nid], lru) {
                if (pin && !is_pinnable_page(page))
                        continue;

                if (PageHWPoison(page))
                        continue;

                list_move(&page->lru, &h->hugepage_activelist);
                set_page_refcounted(page);
                ClearHPageFreed(page);
                h->free_huge_pages--;
                h->free_huge_pages_node[nid]--;
                return page;
        }

        return NULL;
}

static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask, int nid,
                nodemask_t *nmask)
{
        unsigned int cpuset_mems_cookie;
        struct zonelist *zonelist;
        struct zone *zone;
        struct zoneref *z;
        int node = NUMA_NO_NODE;

        zonelist = node_zonelist(nid, gfp_mask);

retry_cpuset:
        cpuset_mems_cookie = read_mems_allowed_begin();
        for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
                struct page *page;

                if (!cpuset_zone_allowed(zone, gfp_mask))
                        continue;
                /*
                 * no need to ask again on the same node. Pool is node rather than
                 * zone aware
                 */
                if (zone_to_nid(zone) == node)
                        continue;
                node = zone_to_nid(zone);

                page = dequeue_huge_page_node_exact(h, node);
                if (page)
                        return page;
        }
        if (unlikely(read_mems_allowed_retry(cpuset_mems_cookie)))
                goto retry_cpuset;

        return NULL;
}

static struct page *dequeue_huge_page_vma(struct hstate *h,
                                struct vm_area_struct *vma,
                                unsigned long address, int avoid_reserve,
                                long chg)
{
        struct page *page = NULL;
        struct mempolicy *mpol;
        gfp_t gfp_mask;
        nodemask_t *nodemask;
        int nid;

        /*
         * A child process with MAP_PRIVATE mappings created by their parent
         * have no page reserves. This check ensures that reservations are
         * not "stolen". The child may still get SIGKILLed
         */
        if (!vma_has_reserves(vma, chg) &&
                        h->free_huge_pages - h->resv_huge_pages == 0)
                goto err;

        /* If reserves cannot be used, ensure enough pages are in the pool */
        if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
                goto err;

        gfp_mask = htlb_alloc_mask(h);
        nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);

        if (mpol_is_preferred_many(mpol)) {
                page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);

                /* Fallback to all nodes if page==NULL */
                nodemask = NULL;
        }

        if (!page)
                page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);

        if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
                SetHPageRestoreReserve(page);
                h->resv_huge_pages--;
        }

        mpol_cond_put(mpol);
        return page;

err:
        return NULL;
}

/*
 * common helper functions for hstate_next_node_to_{alloc|free}.
 * We may have allocated or freed a huge page based on a different
 * nodes_allowed previously, so h->next_node_to_{alloc|free} might
 * be outside of *nodes_allowed.  Ensure that we use an allowed
 * node for alloc or free.
 */
static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
{
        nid = next_node_in(nid, *nodes_allowed);
        VM_BUG_ON(nid >= MAX_NUMNODES);

        return nid;
}

static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
{
        if (!node_isset(nid, *nodes_allowed))
                nid = next_node_allowed(nid, nodes_allowed);
        return nid;
}

/*
 * returns the previously saved node ["this node"] from which to
 * allocate a persistent huge page for the pool and advance the
 * next node from which to allocate, handling wrap at end of node
 * mask.
 */
static int hstate_next_node_to_alloc(struct hstate *h,
                                        nodemask_t *nodes_allowed)
{
        int nid;

        VM_BUG_ON(!nodes_allowed);

        nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
        h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);

        return nid;
}

/*
 * helper for remove_pool_huge_page() - return the previously saved
 * node ["this node"] from which to free a huge page.  Advance the
 * next node id whether or not we find a free huge page to free so
 * that the next attempt to free addresses the next node.
 */
static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
{
        int nid;

        VM_BUG_ON(!nodes_allowed);

        nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
        h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);

        return nid;
}

#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)           \
        for (nr_nodes = nodes_weight(*mask);                            \
                nr_nodes > 0 &&                                         \
                ((node = hstate_next_node_to_alloc(hs, mask)) || 1);    \
                nr_nodes--)

#define for_each_node_mask_to_free(hs, nr_nodes, node, mask)            \
        for (nr_nodes = nodes_weight(*mask);                            \
                nr_nodes > 0 &&                                         \
                ((node = hstate_next_node_to_free(hs, mask)) || 1);     \
                nr_nodes--)

/* used to demote non-gigantic_huge pages as well */
static void __destroy_compound_gigantic_page(struct page *page,
                                        unsigned int order, bool demote)
{
        int i;
        int nr_pages = 1 << order;
        struct page *p = page + 1;

        atomic_set(compound_mapcount_ptr(page), 0);
        atomic_set(compound_pincount_ptr(page), 0);

        for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
                p->mapping = NULL;
                clear_compound_head(p);
                if (!demote)
                        set_page_refcounted(p);
        }

        set_compound_order(page, 0);
        page[1].compound_nr = 0;
        __ClearPageHead(page);
}

static void destroy_compound_hugetlb_page_for_demote(struct page *page,
                                        unsigned int order)
{
        __destroy_compound_gigantic_page(page, order, true);
}

#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
static void destroy_compound_gigantic_page(struct page *page,
                                        unsigned int order)
{
        __destroy_compound_gigantic_page(page, order, false);
}

static void free_gigantic_page(struct page *page, unsigned int order)
{
        /*
         * If the page isn't allocated using the cma allocator,
         * cma_release() returns false.
         */
#ifdef CONFIG_CMA
        if (cma_release(hugetlb_cma[page_to_nid(page)], page, 1 << order))
                return;
#endif

        free_contig_range(page_to_pfn(page), 1 << order);
}

#ifdef CONFIG_CONTIG_ALLOC
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
                int nid, nodemask_t *nodemask)
{
        unsigned long nr_pages = pages_per_huge_page(h);
        if (nid == NUMA_NO_NODE)
                nid = numa_mem_id();

#ifdef CONFIG_CMA
        {
                struct page *page;
                int node;

                if (hugetlb_cma[nid]) {
                        page = cma_alloc(hugetlb_cma[nid], nr_pages,
                                        huge_page_order(h), true);
                        if (page)
                                return page;
                }

                if (!(gfp_mask & __GFP_THISNODE)) {
                        for_each_node_mask(node, *nodemask) {
                                if (node == nid || !hugetlb_cma[node])
                                        continue;

                                page = cma_alloc(hugetlb_cma[node], nr_pages,
                                                huge_page_order(h), true);
                                if (page)
                                        return page;
                        }
                }
        }
#endif

        return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
}

#else /* !CONFIG_CONTIG_ALLOC */
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
                                        int nid, nodemask_t *nodemask)
{
        return NULL;
}
#endif /* CONFIG_CONTIG_ALLOC */

#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
                                        int nid, nodemask_t *nodemask)
{
        return NULL;
}
static inline void free_gigantic_page(struct page *page, unsigned int order) { }
static inline void destroy_compound_gigantic_page(struct page *page,
                                                unsigned int order) { }
#endif

/*
 * Remove hugetlb page from lists, and update dtor so that page appears
 * as just a compound page.
 *
 * A reference is held on the page, except in the case of demote.
 *
 * Must be called with hugetlb lock held.
 */
static void __remove_hugetlb_page(struct hstate *h, struct page *page,
                                                        bool adjust_surplus,
                                                        bool demote)
{
        int nid = page_to_nid(page);

        VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
        VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);

        lockdep_assert_held(&hugetlb_lock);
        if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                return;

        list_del(&page->lru);

        if (HPageFreed(page)) {
                h->free_huge_pages--;
                h->free_huge_pages_node[nid]--;
        }
        if (adjust_surplus) {
                h->surplus_huge_pages--;
                h->surplus_huge_pages_node[nid]--;
        }

        /*
         * Very subtle
         *
         * For non-gigantic pages set the destructor to the normal compound
         * page dtor.  This is needed in case someone takes an additional
         * temporary ref to the page, and freeing is delayed until they drop
         * their reference.
         *
         * For gigantic pages set the destructor to the null dtor.  This
         * destructor will never be called.  Before freeing the gigantic
         * page destroy_compound_gigantic_page will turn the compound page
         * into a simple group of pages.  After this the destructor does not
         * apply.
         *
         * This handles the case where more than one ref is held when and
         * after update_and_free_page is called.
         *
         * In the case of demote we do not ref count the page as it will soon
         * be turned into a page of smaller size.
         */
        if (!demote)
                set_page_refcounted(page);
        if (hstate_is_gigantic(h))
                set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
        else
                set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);

        h->nr_huge_pages--;
        h->nr_huge_pages_node[nid]--;
}

static void remove_hugetlb_page(struct hstate *h, struct page *page,
                                                        bool adjust_surplus)
{
        __remove_hugetlb_page(h, page, adjust_surplus, false);
}

static void remove_hugetlb_page_for_demote(struct hstate *h, struct page *page,
                                                        bool adjust_surplus)
{
        __remove_hugetlb_page(h, page, adjust_surplus, true);
}

static void add_hugetlb_page(struct hstate *h, struct page *page,
                             bool adjust_surplus)
{
        int zeroed;
        int nid = page_to_nid(page);

        VM_BUG_ON_PAGE(!HPageVmemmapOptimized(page), page);

        lockdep_assert_held(&hugetlb_lock);

        INIT_LIST_HEAD(&page->lru);
        h->nr_huge_pages++;
        h->nr_huge_pages_node[nid]++;

        if (adjust_surplus) {
                h->surplus_huge_pages++;
                h->surplus_huge_pages_node[nid]++;
        }

        set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
        set_page_private(page, 0);
        SetHPageVmemmapOptimized(page);

        /*
         * This page is about to be managed by the hugetlb allocator and
         * should have no users.  Drop our reference, and check for others
         * just in case.
         */
        zeroed = put_page_testzero(page);
        if (!zeroed)
                /*
                 * It is VERY unlikely soneone else has taken a ref on
                 * the page.  In this case, we simply return as the
                 * hugetlb destructor (free_huge_page) will be called
                 * when this other ref is dropped.
                 */
                return;

        arch_clear_hugepage_flags(page);
        enqueue_huge_page(h, page);
}

static void __update_and_free_page(struct hstate *h, struct page *page)
{
        int i;
        struct page *subpage = page;

        if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                return;

        if (alloc_huge_page_vmemmap(h, page)) {
                spin_lock_irq(&hugetlb_lock);
                /*
                 * If we cannot allocate vmemmap pages, just refuse to free the
                 * page and put the page back on the hugetlb free list and treat
                 * as a surplus page.
                 */
                add_hugetlb_page(h, page, true);
                spin_unlock_irq(&hugetlb_lock);
                return;
        }

        for (i = 0; i < pages_per_huge_page(h);
             i++, subpage = mem_map_next(subpage, page, i)) {
                subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
                                1 << PG_referenced | 1 << PG_dirty |
                                1 << PG_active | 1 << PG_private |
                                1 << PG_writeback);
        }

        /*
         * Non-gigantic pages demoted from CMA allocated gigantic pages
         * need to be given back to CMA in free_gigantic_page.
         */
        if (hstate_is_gigantic(h) ||
            hugetlb_cma_page(page, huge_page_order(h))) {
                destroy_compound_gigantic_page(page, huge_page_order(h));
                free_gigantic_page(page, huge_page_order(h));
        } else {
                __free_pages(page, huge_page_order(h));
        }
}

/*
 * As update_and_free_page() can be called under any context, so we cannot
 * use GFP_KERNEL to allocate vmemmap pages. However, we can defer the
 * actual freeing in a workqueue to prevent from using GFP_ATOMIC to allocate
 * the vmemmap pages.
 *
 * free_hpage_workfn() locklessly retrieves the linked list of pages to be
 * freed and frees them one-by-one. As the page->mapping pointer is going
 * to be cleared in free_hpage_workfn() anyway, it is reused as the llist_node
 * structure of a lockless linked list of huge pages to be freed.
 */
static LLIST_HEAD(hpage_freelist);

static void free_hpage_workfn(struct work_struct *work)
{
        struct llist_node *node;

        node = llist_del_all(&hpage_freelist);

        while (node) {
                struct page *page;
                struct hstate *h;

                page = container_of((struct address_space **)node,
                                     struct page, mapping);
                node = node->next;
                page->mapping = NULL;
                /*
                 * The VM_BUG_ON_PAGE(!PageHuge(page), page) in page_hstate()
                 * is going to trigger because a previous call to
                 * remove_hugetlb_page() will set_compound_page_dtor(page,
                 * NULL_COMPOUND_DTOR), so do not use page_hstate() directly.
                 */
                h = size_to_hstate(page_size(page));

                __update_and_free_page(h, page);

                cond_resched();
        }
}
static DECLARE_WORK(free_hpage_work, free_hpage_workfn);

static inline void flush_free_hpage_work(struct hstate *h)
{
        if (free_vmemmap_pages_per_hpage(h))
                flush_work(&free_hpage_work);
}

static void update_and_free_page(struct hstate *h, struct page *page,
                                 bool atomic)
{
        if (!HPageVmemmapOptimized(page) || !atomic) {
                __update_and_free_page(h, page);
                return;
        }

        /*
         * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap pages.
         *
         * Only call schedule_work() if hpage_freelist is previously
         * empty. Otherwise, schedule_work() had been called but the workfn
         * hasn't retrieved the list yet.
         */
        if (llist_add((struct llist_node *)&page->mapping, &hpage_freelist))
                schedule_work(&free_hpage_work);
}

static void update_and_free_pages_bulk(struct hstate *h, struct list_head *list)
{
        struct page *page, *t_page;

        list_for_each_entry_safe(page, t_page, list, lru) {
                update_and_free_page(h, page, false);
                cond_resched();
        }
}

struct hstate *size_to_hstate(unsigned long size)
{
        struct hstate *h;

        for_each_hstate(h) {
                if (huge_page_size(h) == size)
                        return h;
        }
        return NULL;
}

void free_huge_page(struct page *page)
{
        /*
         * Can't pass hstate in here because it is called from the
         * compound page destructor.
         */
        struct hstate *h = page_hstate(page);
        int nid = page_to_nid(page);
        struct hugepage_subpool *spool = hugetlb_page_subpool(page);
        bool restore_reserve;
        unsigned long flags;

        VM_BUG_ON_PAGE(page_count(page), page);
        VM_BUG_ON_PAGE(page_mapcount(page), page);

        hugetlb_set_page_subpool(page, NULL);
        page->mapping = NULL;
        restore_reserve = HPageRestoreReserve(page);
        ClearHPageRestoreReserve(page);

        /*
         * If HPageRestoreReserve was set on page, page allocation consumed a
         * reservation.  If the page was associated with a subpool, there
         * would have been a page reserved in the subpool before allocation
         * via hugepage_subpool_get_pages().  Since we are 'restoring' the
         * reservation, do not call hugepage_subpool_put_pages() as this will
         * remove the reserved page from the subpool.
         */
        if (!restore_reserve) {
                /*
                 * A return code of zero implies that the subpool will be
                 * under its minimum size if the reservation is not restored
                 * after page is free.  Therefore, force restore_reserve
                 * operation.
                 */
                if (hugepage_subpool_put_pages(spool, 1) == 0)
                        restore_reserve = true;
        }

        spin_lock_irqsave(&hugetlb_lock, flags);
        ClearHPageMigratable(page);
        hugetlb_cgroup_uncharge_page(hstate_index(h),
                                     pages_per_huge_page(h), page);
        hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
                                          pages_per_huge_page(h), page);
        if (restore_reserve)
                h->resv_huge_pages++;

        if (HPageTemporary(page)) {
                remove_hugetlb_page(h, page, false);
                spin_unlock_irqrestore(&hugetlb_lock, flags);
                update_and_free_page(h, page, true);
        } else if (h->surplus_huge_pages_node[nid]) {
                /* remove the page from active list */
                remove_hugetlb_page(h, page, true);
                spin_unlock_irqrestore(&hugetlb_lock, flags);
                update_and_free_page(h, page, true);
        } else {
                arch_clear_hugepage_flags(page);
                enqueue_huge_page(h, page);
                spin_unlock_irqrestore(&hugetlb_lock, flags);
        }
}

/*
 * Must be called with the hugetlb lock held
 */
static void __prep_account_new_huge_page(struct hstate *h, int nid)
{
        lockdep_assert_held(&hugetlb_lock);
        h->nr_huge_pages++;
        h->nr_huge_pages_node[nid]++;
}

static void __prep_new_huge_page(struct hstate *h, struct page *page)
{
        free_huge_page_vmemmap(h, page);
        INIT_LIST_HEAD(&page->lru);
        set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
        hugetlb_set_page_subpool(page, NULL);
        set_hugetlb_cgroup(page, NULL);
        set_hugetlb_cgroup_rsvd(page, NULL);
}

static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
{
        __prep_new_huge_page(h, page);
        spin_lock_irq(&hugetlb_lock);
        __prep_account_new_huge_page(h, nid);
        spin_unlock_irq(&hugetlb_lock);
}

static bool __prep_compound_gigantic_page(struct page *page, unsigned int order,
                                                                bool demote)
{
        int i, j;
        int nr_pages = 1 << order;
        struct page *p = page + 1;

        /* we rely on prep_new_huge_page to set the destructor */
        set_compound_order(page, order);
        __ClearPageReserved(page);
        __SetPageHead(page);
        for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
                /*
                 * For gigantic hugepages allocated through bootmem at
                 * boot, it's safer to be consistent with the not-gigantic
                 * hugepages and clear the PG_reserved bit from all tail pages
                 * too.  Otherwise drivers using get_user_pages() to access tail
                 * pages may get the reference counting wrong if they see
                 * PG_reserved set on a tail page (despite the head page not
                 * having PG_reserved set).  Enforcing this consistency between
                 * head and tail pages allows drivers to optimize away a check
                 * on the head page when they need know if put_page() is needed
                 * after get_user_pages().
                 */
                __ClearPageReserved(p);
                /*
                 * Subtle and very unlikely
                 *
                 * Gigantic 'page allocators' such as memblock or cma will
                 * return a set of pages with each page ref counted.  We need
                 * to turn this set of pages into a compound page with tail
                 * page ref counts set to zero.  Code such as speculative page
                 * cache adding could take a ref on a 'to be' tail page.
                 * We need to respect any increased ref count, and only set
                 * the ref count to zero if count is currently 1.  If count
                 * is not 1, we return an error.  An error return indicates
                 * the set of pages can not be converted to a gigantic page.
                 * The caller who allocated the pages should then discard the
                 * pages using the appropriate free interface.
                 *
                 * In the case of demote, the ref count will be zero.
                 */
                if (!demote) {
                        if (!page_ref_freeze(p, 1)) {
                                pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n");
                                goto out_error;
                        }
                } else {
                        VM_BUG_ON_PAGE(page_count(p), p);
                }
                set_compound_head(p, page);
        }
        atomic_set(compound_mapcount_ptr(page), -1);
        atomic_set(compound_pincount_ptr(page), 0);
        return true;

out_error:
        /* undo tail page modifications made above */
        p = page + 1;
        for (j = 1; j < i; j++, p = mem_map_next(p, page, j)) {
                clear_compound_head(p);
                set_page_refcounted(p);
        }
        /* need to clear PG_reserved on remaining tail pages  */
        for (; j < nr_pages; j++, p = mem_map_next(p, page, j))
                __ClearPageReserved(p);
        set_compound_order(page, 0);
        page[1].compound_nr = 0;
        __ClearPageHead(page);
        return false;
}

static bool prep_compound_gigantic_page(struct page *page, unsigned int order)
{
        return __prep_compound_gigantic_page(page, order, false);
}

static bool prep_compound_gigantic_page_for_demote(struct page *page,
                                                        unsigned int order)
{
        return __prep_compound_gigantic_page(page, order, true);
}

/*
 * PageHuge() only returns true for hugetlbfs pages, but not for normal or
 * transparent huge pages.  See the PageTransHuge() documentation for more
 * details.
 */
int PageHuge(struct page *page)
{
        if (!PageCompound(page))
                return 0;

        page = compound_head(page);
        return page[1].compound_dtor == HUGETLB_PAGE_DTOR;
}
EXPORT_SYMBOL_GPL(PageHuge);

/*
 * PageHeadHuge() only returns true for hugetlbfs head page, but not for
 * normal or transparent huge pages.
 */
int PageHeadHuge(struct page *page_head)
{
        if (!PageHead(page_head))
                return 0;

        return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
}

/*
 * Find and lock address space (mapping) in write mode.
 *
 * Upon entry, the page is locked which means that page_mapping() is
 * stable.  Due to locking order, we can only trylock_write.  If we can
 * not get the lock, simply return NULL to caller.
 */
struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage)
{
        struct address_space *mapping = page_mapping(hpage);

        if (!mapping)
                return mapping;

        if (i_mmap_trylock_write(mapping))
                return mapping;

        return NULL;
}

pgoff_t hugetlb_basepage_index(struct page *page)
{
        struct page *page_head = compound_head(page);
        pgoff_t index = page_index(page_head);
        unsigned long compound_idx;

        if (compound_order(page_head) >= MAX_ORDER)
                compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
        else
                compound_idx = page - page_head;

        return (index << compound_order(page_head)) + compound_idx;
}

static struct page *alloc_buddy_huge_page(struct hstate *h,
                gfp_t gfp_mask, int nid, nodemask_t *nmask,
                nodemask_t *node_alloc_noretry)
{
        int order = huge_page_order(h);
        struct page *page;
        bool alloc_try_hard = true;

        /*
         * By default we always try hard to allocate the page with
         * __GFP_RETRY_MAYFAIL flag.  However, if we are allocating pages in
         * a loop (to adjust global huge page counts) and previous allocation
         * failed, do not continue to try hard on the same node.  Use the
         * node_alloc_noretry bitmap to manage this state information.
         */
        if (node_alloc_noretry && node_isset(nid, *node_alloc_noretry))
                alloc_try_hard = false;
        gfp_mask |= __GFP_COMP|__GFP_NOWARN;
        if (alloc_try_hard)
                gfp_mask |= __GFP_RETRY_MAYFAIL;
        if (nid == NUMA_NO_NODE)
                nid = numa_mem_id();
        page = __alloc_pages(gfp_mask, order, nid, nmask);
        if (page)
                __count_vm_event(HTLB_BUDDY_PGALLOC);
        else
                __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);

        /*
         * If we did not specify __GFP_RETRY_MAYFAIL, but still got a page this
         * indicates an overall state change.  Clear bit so that we resume
         * normal 'try hard' allocations.
         */
        if (node_alloc_noretry && page && !alloc_try_hard)
                node_clear(nid, *node_alloc_noretry);

        /*
         * If we tried hard to get a page but failed, set bit so that
         * subsequent attempts will not try as hard until there is an
         * overall state change.
         */
        if (node_alloc_noretry && !page && alloc_try_hard)
                node_set(nid, *node_alloc_noretry);

        return page;
}

/*
 * Common helper to allocate a fresh hugetlb page. All specific allocators
 * should use this function to get new hugetlb pages
 */
static struct page *alloc_fresh_huge_page(struct hstate *h,
                gfp_t gfp_mask, int nid, nodemask_t *nmask,
                nodemask_t *node_alloc_noretry)
{
        struct page *page;
        bool retry = false;

retry:
        if (hstate_is_gigantic(h))
                page = alloc_gigantic_page(h, gfp_mask, nid, nmask);
        else
                page = alloc_buddy_huge_page(h, gfp_mask,
                                nid, nmask, node_alloc_noretry);
        if (!page)
                return NULL;

        if (hstate_is_gigantic(h)) {
                if (!prep_compound_gigantic_page(page, huge_page_order(h))) {
                        /*
                         * Rare failure to convert pages to compound page.
                         * Free pages and try again - ONCE!
                         */
                        free_gigantic_page(page, huge_page_order(h));
                        if (!retry) {
                                retry = true;
                                goto retry;
                        }
                        return NULL;
                }
        }
        prep_new_huge_page(h, page, page_to_nid(page));

        return page;
}

/*
 * Allocates a fresh page to the hugetlb allocator pool in the node interleaved
 * manner.
 */
static int alloc_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
                                nodemask_t *node_alloc_noretry)
{
        struct page *page;
        int nr_nodes, node;
        gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;

        for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
                page = alloc_fresh_huge_page(h, gfp_mask, node, nodes_allowed,
                                                node_alloc_noretry);
                if (page)
                        break;
        }

        if (!page)
                return 0;

        put_page(page); /* free it into the hugepage allocator */

        return 1;
}

/*
 * Remove huge page from pool from next node to free.  Attempt to keep
 * persistent huge pages more or less balanced over allowed nodes.
 * This routine only 'removes' the hugetlb page.  The caller must make
 * an additional call to free the page to low level allocators.
 * Called with hugetlb_lock locked.
 */
static struct page *remove_pool_huge_page(struct hstate *h,
                                                nodemask_t *nodes_allowed,
                                                 bool acct_surplus)
{
        int nr_nodes, node;
        struct page *page = NULL;

        lockdep_assert_held(&hugetlb_lock);
        for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
                /*
                 * If we're returning unused surplus pages, only examine
                 * nodes with surplus pages.
                 */
                if ((!acct_surplus || h->surplus_huge_pages_node[node]) &&
                    !list_empty(&h->hugepage_freelists[node])) {
                        page = list_entry(h->hugepage_freelists[node].next,
                                          struct page, lru);
                        remove_hugetlb_page(h, page, acct_surplus);
                        break;
                }
        }

        return page;
}

/*
 * Dissolve a given free hugepage into free buddy pages. This function does
 * nothing for in-use hugepages and non-hugepages.
 * This function returns values like below:
 *
 *  -ENOMEM: failed to allocate vmemmap pages to free the freed hugepages
 *           when the system is under memory pressure and the feature of
 *           freeing unused vmemmap pages associated with each hugetlb page
 *           is enabled.
 *  -EBUSY:  failed to dissolved free hugepages or the hugepage is in-use
 *           (allocated or reserved.)
 *       0:  successfully dissolved free hugepages or the page is not a
 *           hugepage (considered as already dissolved)
 */
int dissolve_free_huge_page(struct page *page)
{
        int rc = -EBUSY;

retry:
        /* Not to disrupt normal path by vainly holding hugetlb_lock */
        if (!PageHuge(page))
                return 0;

        spin_lock_irq(&hugetlb_lock);
        if (!PageHuge(page)) {
                rc = 0;
                goto out;
        }

        if (!page_count(page)) {
                struct page *head = compound_head(page);
                struct hstate *h = page_hstate(head);
                if (h->free_huge_pages - h->resv_huge_pages == 0)
                        goto out;

                /*
                 * We should make sure that the page is already on the free list
                 * when it is dissolved.
                 */
                if (unlikely(!HPageFreed(head))) {
                        spin_unlock_irq(&hugetlb_lock);
                        cond_resched();

                        /*
                         * Theoretically, we should return -EBUSY when we
                         * encounter this race. In fact, we have a chance
                         * to successfully dissolve the page if we do a
                         * retry. Because the race window is quite small.
                         * If we seize this opportunity, it is an optimization
                         * for increasing the success rate of dissolving page.
                         */
                        goto retry;
                }

                remove_hugetlb_page(h, head, false);
                h->max_huge_pages--;
                spin_unlock_irq(&hugetlb_lock);

                /*
                 * Normally update_and_free_page will allocate required vmemmmap
                 * before freeing the page.  update_and_free_page will fail to
                 * free the page if it can not allocate required vmemmap.  We
                 * need to adjust max_huge_pages if the page is not freed.
                 * Attempt to allocate vmemmmap here so that we can take
                 * appropriate action on failure.
                 */
                rc = alloc_huge_page_vmemmap(h, head);
                if (!rc) {
                        /*
                         * Move PageHWPoison flag from head page to the raw
                         * error page, which makes any subpages rather than
                         * the error page reusable.
                         */
                        if (PageHWPoison(head) && page != head) {
                                SetPageHWPoison(page);
                                ClearPageHWPoison(head);
                        }
                        update_and_free_page(h, head, false);
                } else {
                        spin_lock_irq(&hugetlb_lock);
                        add_hugetlb_page(h, head, false);
                        h->max_huge_pages++;
                        spin_unlock_irq(&hugetlb_lock);
                }

                return rc;
        }
out:
        spin_unlock_irq(&hugetlb_lock);
        return rc;
}

/*
 * Dissolve free hugepages in a given pfn range. Used by memory hotplug to
 * make specified memory blocks removable from the system.
 * Note that this will dissolve a free gigantic hugepage completely, if any
 * part of it lies within the given range.
 * Also note that if dissolve_free_huge_page() returns with an error, all
 * free hugepages that were dissolved before that error are lost.
 */
int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
{
        unsigned long pfn;
        struct page *page;
        int rc = 0;

        if (!hugepages_supported())
                return rc;

        for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
                page = pfn_to_page(pfn);
                rc = dissolve_free_huge_page(page);
                if (rc)
                        break;
        }

        return rc;
}

/*
 * Allocates a fresh surplus page from the page allocator.
 */
static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
                int nid, nodemask_t *nmask, bool zero_ref)
{
        struct page *page = NULL;
        bool retry = false;

        if (hstate_is_gigantic(h))
                return NULL;

        spin_lock_irq(&hugetlb_lock);
        if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages)
                goto out_unlock;
        spin_unlock_irq(&hugetlb_lock);

retry:
        page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
        if (!page)
                return NULL;

        spin_lock_irq(&hugetlb_lock);
        /*
         * We could have raced with the pool size change.
         * Double check that and simply deallocate the new page
         * if we would end up overcommiting the surpluses. Abuse
         * temporary page to workaround the nasty free_huge_page
         * codeflow
         */
        if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
                SetHPageTemporary(page);
                spin_unlock_irq(&hugetlb_lock);
                put_page(page);
                return NULL;
        }

        if (zero_ref) {
                /*
                 * Caller requires a page with zero ref count.
                 * We will drop ref count here.  If someone else is holding
                 * a ref, the page will be freed when they drop it.  Abuse
                 * temporary page flag to accomplish this.
                 */
                SetHPageTemporary(page);
                if (!put_page_testzero(page)) {
                        /*
                         * Unexpected inflated ref count on freshly allocated
                         * huge.  Retry once.
                         */
                        pr_info("HugeTLB unexpected inflated ref count on freshly allocated page\n");
                        spin_unlock_irq(&hugetlb_lock);
                        if (retry)
                                return NULL;

                        retry = true;
                        goto retry;
                }
                ClearHPageTemporary(page);
        }

        h->surplus_huge_pages++;
        h->surplus_huge_pages_node[page_to_nid(page)]++;

out_unlock:
        spin_unlock_irq(&hugetlb_lock);

        return page;
}

static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
                                     int nid, nodemask_t *nmask)
{
        struct page *page;

        if (hstate_is_gigantic(h))
                return NULL;

        page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
        if (!page)
                return NULL;

        /*
         * We do not account these pages as surplus because they are only
         * temporary and will be released properly on the last reference
         */
        SetHPageTemporary(page);

        return page;
}

/*
 * Use the VMA's mpolicy to allocate a huge page from the buddy.
 */
static
struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
                struct vm_area_struct *vma, unsigned long addr)
{
        struct page *page = NULL;
        struct mempolicy *mpol;
        gfp_t gfp_mask = htlb_alloc_mask(h);
        int nid;
        nodemask_t *nodemask;

        nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
        if (mpol_is_preferred_many(mpol)) {
                gfp_t gfp = gfp_mask | __GFP_NOWARN;

                gfp &=  ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
                page = alloc_surplus_huge_page(h, gfp, nid, nodemask, false);

                /* Fallback to all nodes if page==NULL */
                nodemask = NULL;
        }

        if (!page)
                page = alloc_surplus_huge_page(h, gfp_mask, nid, nodemask, false);
        mpol_cond_put(mpol);
        return page;
}

/* page migration callback function */
struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
                nodemask_t *nmask, gfp_t gfp_mask)
{
        spin_lock_irq(&hugetlb_lock);
        if (h->free_huge_pages - h->resv_huge_pages > 0) {
                struct page *page;

                page = dequeue_huge_page_nodemask(h, gfp_mask, preferred_nid, nmask);
                if (page) {
                        spin_unlock_irq(&hugetlb_lock);
                        return page;
                }
        }
        spin_unlock_irq(&hugetlb_lock);

        return alloc_migrate_huge_page(h, gfp_mask, preferred_nid, nmask);
}

/* mempolicy aware migration callback */
struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
                unsigned long address)
{
        struct mempolicy *mpol;
        nodemask_t *nodemask;
        struct page *page;
        gfp_t gfp_mask;
        int node;

        gfp_mask = htlb_alloc_mask(h);
        node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
        page = alloc_huge_page_nodemask(h, node, nodemask, gfp_mask);
        mpol_cond_put(mpol);

        return page;
}

/*
 * Increase the hugetlb pool such that it can accommodate a reservation
 * of size 'delta'.
 */
static int gather_surplus_pages(struct hstate *h, long delta)
        __must_hold(&hugetlb_lock)
{
        struct list_head surplus_list;
        struct page *page, *tmp;
        int ret;
        long i;
        long needed, allocated;
        bool alloc_ok = true;

        lockdep_assert_held(&hugetlb_lock);
        needed = (h->resv_huge_pages + delta) - h->free_huge_pages;
        if (needed <= 0) {
                h->resv_huge_pages += delta;
                return 0;
        }

        allocated = 0;
        INIT_LIST_HEAD(&surplus_list);

        ret = -ENOMEM;
retry:
        spin_unlock_irq(&hugetlb_lock);
        for (i = 0; i < needed; i++) {
                page = alloc_surplus_huge_page(h, htlb_alloc_mask(h),
                                NUMA_NO_NODE, NULL, true);
                if (!page) {
                        alloc_ok = false;
                        break;
                }
                list_add(&page->lru, &surplus_list);
                cond_resched();
        }
        allocated += i;

        /*
         * After retaking hugetlb_lock, we need to recalculate 'needed'
         * because either resv_huge_pages or free_huge_pages may have changed.
         */
        spin_lock_irq(&hugetlb_lock);
        needed = (h->resv_huge_pages + delta) -
                        (h->free_huge_pages + allocated);
        if (needed > 0) {
                if (alloc_ok)
                        goto retry;
                /*
                 * We were not able to allocate enough pages to
                 * satisfy the entire reservation so we free what
                 * we've allocated so far.
                 */
                goto free;
        }
        /*
         * The surplus_list now contains _at_least_ the number of extra pages
         * needed to accommodate the reservation.  Add the appropriate number
         * of pages to the hugetlb pool and free the extras back to the buddy
         * allocator.  Commit the entire reservation here to prevent another
         * process from stealing the pages as they are added to the pool but
         * before they are reserved.
         */
        needed += allocated;
        h->resv_huge_pages += delta;
        ret = 0;

        /* Free the needed pages to the hugetlb pool */
        list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
                if ((--needed) < 0)
                        break;
                /* Add the page to the hugetlb allocator */
                enqueue_huge_page(h, page);
        }
free:
        spin_unlock_irq(&hugetlb_lock);

        /*
         * Free unnecessary surplus pages to the buddy allocator.
         * Pages have no ref count, call free_huge_page directly.
         */
        list_for_each_entry_safe(page, tmp, &surplus_list, lru)
                free_huge_page(page);
        spin_lock_irq(&hugetlb_lock);

        return ret;
}

/*
 * This routine has two main purposes:
 * 1) Decrement the reservation count (resv_huge_pages) by the value passed
 *    in unused_resv_pages.  This corresponds to the prior adjustments made
 *    to the associated reservation map.
 * 2) Free any unused surplus pages that may have been allocated to satisfy
 *    the reservation.  As many as unused_resv_pages may be freed.
 */
static void return_unused_surplus_pages(struct hstate *h,
                                        unsigned long unused_resv_pages)
{
        unsigned long nr_pages;
        struct page *page;
        LIST_HEAD(page_list);

        lockdep_assert_held(&hugetlb_lock);
        /* Uncommit the reservation */
        h->resv_huge_pages -= unused_resv_pages;

        /* Cannot return gigantic pages currently */
        if (hstate_is_gigantic(h))
                goto out;

        /*
         * Part (or even all) of the reservation could have been backed
         * by pre-allocated pages. Only free surplus pages.
         */
        nr_pages = min(unused_resv_pages, h->surplus_huge_pages);

        /*
         * We want to release as many surplus pages as possible, spread
         * evenly across all nodes with memory. Iterate across these nodes
         * until we can no longer free unreserved surplus pages. This occurs
         * when the nodes with surplus pages have no free pages.
         * remove_pool_huge_page() will balance the freed pages across the
         * on-line nodes with memory and will handle the hstate accounting.
         */
        while (nr_pages--) {
                page = remove_pool_huge_page(h, &node_states[N_MEMORY], 1);
                if (!page)
                        goto out;

                list_add(&page->lru, &page_list);
        }

out:
        spin_unlock_irq(&hugetlb_lock);
        update_and_free_pages_bulk(h, &page_list);
        spin_lock_irq(&hugetlb_lock);
}


/*
 * vma_needs_reservation, vma_commit_reservation and vma_end_reservation
 * are used by the huge page allocation routines to manage reservations.
 *
 * vma_needs_reservation is called to determine if the huge page at addr
 * within the vma has an associated reservation.  If a reservation is
 * needed, the value 1 is returned.  The caller is then responsible for
 * managing the global reservation and subpool usage counts.  After
 * the huge page has been allocated, vma_commit_reservation is called
 * to add the page to the reservation map.  If the page allocation fails,
 * the reservation must be ended instead of committed.  vma_end_reservation
 * is called in such cases.
 *
 * In the normal case, vma_commit_reservation returns the same value
 * as the preceding vma_needs_reservation call.  The only time this
 * is not the case is if a reserve map was changed between calls.  It
 * is the responsibility of the caller to notice the difference and
 * take appropriate action.
 *
 * vma_add_reservation is used in error paths where a reservation must
 * be restored when a newly allocated huge page must be freed.  It is
 * to be called after calling vma_needs_reservation to determine if a
 * reservation exists.
 *
 * vma_del_reservation is used in error paths where an entry in the reserve
 * map was created during huge page allocation and must be removed.  It is to
 * be called after calling vma_needs_reservation to determine if a reservation
 * exists.
 */
enum vma_resv_mode {
        VMA_NEEDS_RESV,
        VMA_COMMIT_RESV,
        VMA_END_RESV,
        VMA_ADD_RESV,
        VMA_DEL_RESV,
};
static long __vma_reservation_common(struct hstate *h,
                                struct vm_area_struct *vma, unsigned long addr,
                                enum vma_resv_mode mode)
{
        struct resv_map *resv;
        pgoff_t idx;
        long ret;
        long dummy_out_regions_needed;

        resv = vma_resv_map(vma);
        if (!resv)
                return 1;

        idx = vma_hugecache_offset(h, vma, addr);
        switch (mode) {
        case VMA_NEEDS_RESV:
                ret = region_chg(resv, idx, idx + 1, &dummy_out_regions_needed);
                /* We assume that vma_reservation_* routines always operate on
                 * 1 page, and that adding to resv map a 1 page entry can only
                 * ever require 1 region.
                 */
                VM_BUG_ON(dummy_out_regions_needed != 1);
                break;
        case VMA_COMMIT_RESV:
                ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                /* region_add calls of range 1 should never fail. */
                VM_BUG_ON(ret < 0);
                break;
        case VMA_END_RESV:
                region_abort(resv, idx, idx + 1, 1);
                ret = 0;
                break;
        case VMA_ADD_RESV:
                if (vma->vm_flags & VM_MAYSHARE) {
                        ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                        /* region_add calls of range 1 should never fail. */
                        VM_BUG_ON(ret < 0);
                } else {
                        region_abort(resv, idx, idx + 1, 1);
                        ret = region_del(resv, idx, idx + 1);
                }
                break;
        case VMA_DEL_RESV:
                if (vma->vm_flags & VM_MAYSHARE) {
                        region_abort(resv, idx, idx + 1, 1);
                        ret = region_del(resv, idx, idx + 1);
                } else {
                        ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                        /* region_add calls of range 1 should never fail. */
                        VM_BUG_ON(ret < 0);
                }
                break;
        default:
                BUG();
        }

        if (vma->vm_flags & VM_MAYSHARE || mode == VMA_DEL_RESV)
                return ret;
        /*
         * We know private mapping must have HPAGE_RESV_OWNER set.
         *
         * In most cases, reserves always exist for private mappings.
         * However, a file associated with mapping could have been
         * hole punched or truncated after reserves were consumed.
         * As subsequent fault on such a range will not use reserves.
         * Subtle - The reserve map for private mappings has the
         * opposite meaning than that of shared mappings.  If NO
         * entry is in the reserve map, it means a reservation exists.
         * If an entry exists in the reserve map, it means the
         * reservation has already been consumed.  As a result, the
         * return value of this routine is the opposite of the
         * value returned from reserve map manipulation routines above.
         */
        if (ret > 0)
                return 0;
        if (ret == 0)
                return 1;
        return ret;
}

static long vma_needs_reservation(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long addr)
{
        return __vma_reservation_common(h, vma, addr, VMA_NEEDS_RESV);
}

static long vma_commit_reservation(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long addr)
{
        return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV);
}

static void vma_end_reservation(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long addr)
{
        (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV);
}

static long vma_add_reservation(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long addr)
{
        return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV);
}

static long vma_del_reservation(struct hstate *h,
                        struct vm_area_struct *vma, unsigned long addr)
{
        return __vma_reservation_common(h, vma, addr, VMA_DEL_RESV);
}

/*
 * This routine is called to restore reservation information on error paths.
 * It should ONLY be called for pages allocated via alloc_huge_page(), and
 * the hugetlb mutex should remain held when calling this routine.
 *
 * It handles two specific cases:
 * 1) A reservation was in place and the page consumed the reservation.
 *    HPageRestoreReserve is set in the page.
 * 2) No reservation was in place for the page, so HPageRestoreReserve is
 *    not set.  However, alloc_huge_page always updates the reserve map.
 *
 * In case 1, free_huge_page later in the error path will increment the
 * global reserve count.  But, free_huge_page does not have enough context
 * to adjust the reservation map.  This case deals primarily with private
 * mappings.  Adjust the reserve map here to be consistent with global
 * reserve count adjustments to be made by free_huge_page.  Make sure the
 * reserve map indicates there is a reservation present.
 *
 * In case 2, simply undo reserve map modifications done by alloc_huge_page.
 */
void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
                        unsigned long address, struct page *page)
{
        long rc = vma_needs_reservation(h, vma, address);

        if (HPageRestoreReserve(page)) {
                if (unlikely(rc < 0))
                        /*
                         * Rare out of memory condition in reserve map
                         * manipulation.  Clear HPageRestoreReserve so that
                         * global reserve count will not be incremented
                         * by free_huge_page.  This will make it appear
                         * as though the reservation for this page was
                         * consumed.  This may prevent the task from
                         * faulting in the page at a later time.  This
                         * is better than inconsistent global huge page
                         * accounting of reserve counts.
                         */
                        ClearHPageRestoreReserve(page);
                else if (rc)
                        (void)vma_add_reservation(h, vma, address);
                else
                        vma_end_reservation(h, vma, address);
        } else {
                if (!rc) {
                        /*
                         * This indicates there is an entry in the reserve map
                         * not added by alloc_huge_page.  We know it was added
                         * before the alloc_huge_page call, otherwise
                         * HPageRestoreReserve would be set on the page.
                         * Remove the entry so that a subsequent allocation
                         * does not consume a reservation.
                         */
                        rc = vma_del_reservation(h, vma, address);
                        if (rc < 0)
                                /*
                                 * VERY rare out of memory condition.  Since
                                 * we can not delete the entry, set
                                 * HPageRestoreReserve so that the reserve
                                 * count will be incremented when the page
                                 * is freed.  This reserve will be consumed
                                 * on a subsequent allocation.
                                 */
                                SetHPageRestoreReserve(page);
                } else if (rc < 0) {
                        /*
                         * Rare out of memory condition from
                         * vma_needs_reservation call.  Memory allocation is
                         * only attempted if a new entry is needed.  Therefore,
                         * this implies there is not an entry in the
                         * reserve map.
                         *
                         * For shared mappings, no entry in the map indicates
                         * no reservation.  We are done.
                         */
                        if (!(vma->vm_flags & VM_MAYSHARE))
                                /*
                                 * For private mappings, no entry indicates
                                 * a reservation is present.  Since we can
                                 * not add an entry, set SetHPageRestoreReserve
                                 * on the page so reserve count will be
                                 * incremented when freed.  This reserve will
                                 * be consumed on a subsequent allocation.
                                 */
                                SetHPageRestoreReserve(page);
                } else
                        /*
                         * No reservation present, do nothing
                         */
                         vma_end_reservation(h, vma, address);
        }
}

/*
 * alloc_and_dissolve_huge_page - Allocate a new page and dissolve the old one
 * @h: struct hstate old page belongs to
 * @old_page: Old page to dissolve
 * @list: List to isolate the page in case we need to
 * Returns 0 on success, otherwise negated error.
 */
static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
                                        struct list_head *list)
{
        gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
        int nid = page_to_nid(old_page);
        bool alloc_retry = false;
        struct page *new_page;
        int ret = 0;

        /*
         * Before dissolving the page, we need to allocate a new one for the
         * pool to remain stable.  Here, we allocate the page and 'prep' it
         * by doing everything but actually updating counters and adding to
         * the pool.  This simplifies and let us do most of the processing
         * under the lock.
         */
alloc_retry:
        new_page = alloc_buddy_huge_page(h, gfp_mask, nid, NULL, NULL);
        if (!new_page)
                return -ENOMEM;
        /*
         * If all goes well, this page will be directly added to the free
         * list in the pool.  For this the ref count needs to be zero.
         * Attempt to drop now, and retry once if needed.  It is VERY
         * unlikely there is another ref on the page.
         *
         * If someone else has a reference to the page, it will be freed
         * when they drop their ref.  Abuse temporary page flag to accomplish
         * this.  Retry once if there is an inflated ref count.
         */
        SetHPageTemporary(new_page);
        if (!put_page_testzero(new_page)) {
                if (alloc_retry)
                        return -EBUSY;

                alloc_retry = true;
                goto alloc_retry;
        }
        ClearHPageTemporary(new_page);

        __prep_new_huge_page(h, new_page);

retry:
        spin_lock_irq(&hugetlb_lock);
        if (!PageHuge(old_page)) {
                /*
                 * Freed from under us. Drop new_page too.
                 */
                goto free_new;
        } else if (page_count(old_page)) {
                /*
                 * Someone has grabbed the page, try to isolate it here.
                 * Fail with -EBUSY if not possible.
                 */
                spin_unlock_irq(&hugetlb_lock);
                if (!isolate_huge_page(old_page, list))
                        ret = -EBUSY;
                spin_lock_irq(&hugetlb_lock);
                goto free_new;
        } else if (!HPageFreed(old_page)) {
                /*
                 * Page's refcount is 0 but it has not been enqueued in the
                 * freelist yet. Race window is small, so we can succeed here if
                 * we retry.
                 */
                spin_unlock_irq(&hugetlb_lock);
                cond_resched();
                goto retry;
        } else {
                /*
                 * Ok, old_page is still a genuine free hugepage. Remove it from
                 * the freelist and decrease the counters. These will be
                 * incremented again when calling __prep_account_new_huge_page()
                 * and enqueue_huge_page() for new_page. The counters will remain
                 * stable since this happens under the lock.
                 */
                remove_hugetlb_page(h, old_page, false);

                /*
                 * Ref count on new page is already zero as it was dropped
                 * earlier.  It can be directly added to the pool free list.
                 */
                __prep_account_new_huge_page(h, nid);
                enqueue_huge_page(h, new_page);

                /*
                 * Pages have been replaced, we can safely free the old one.
                 */
                spin_unlock_irq(&hugetlb_lock);
                update_and_free_page(h, old_page, false);
        }

        return ret;

free_new:
        spin_unlock_irq(&hugetlb_lock);
        /* Page has a zero ref count, but needs a ref to be freed */
        set_page_refcounted(new_page);
        update_and_free_page(h, new_page, false);

        return ret;
}

int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
{
        struct hstate *h;
        struct page *head;
        int ret = -EBUSY;

        /*
         * The page might have been dissolved from under our feet, so make sure
         * to carefully check the state under the lock.
         * Return success when racing as if we dissolved the page ourselves.
         */
        spin_lock_irq(&hugetlb_lock);
        if (PageHuge(page)) {
                head = compound_head(page);
                h = page_hstate(head);
        } else {
                spin_unlock_irq(&hugetlb_lock);
                return 0;
        }
        spin_unlock_irq(&hugetlb_lock);

        /*
         * Fence off gigantic pages as there is a cyclic dependency between
         * alloc_contig_range and them. Return -ENOMEM as this has the effect
         * of bailing out right away without further retrying.
         */
        if (hstate_is_gigantic(h))
                return -ENOMEM;

        if (page_count(head) && isolate_huge_page(head, list))
                ret = 0;
        else if (!page_count(head))
                ret = alloc_and_dissolve_huge_page(h, head, list);

        return ret;
}

struct page *alloc_huge_page(struct vm_area_struct *vma,
                                    unsigned long addr, int avoid_reserve)
{
        struct hugepage_subpool *spool = subpool_vma(vma);
        struct hstate *h = hstate_vma(vma);
        struct page *page;
        long map_chg, map_commit;
        long gbl_chg;
        int ret, idx;
        struct hugetlb_cgroup *h_cg;
        bool deferred_reserve;

        idx = hstate_index(h);
        /*
         * Examine the region/reserve map to determine if the process
         * has a reservation for the page to be allocated.  A return
         * code of zero indicates a reservation exists (no change).
         */
        map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);
        if (map_chg < 0)
                return ERR_PTR(-ENOMEM);

        /*
         * Processes that did not create the mapping will have no
         * reserves as indicated by the region/reserve map. Check
         * that the allocation will not exceed the subpool limit.
         * Allocations for MAP_NORESERVE mappings also need to be
         * checked against any subpool limit.
         */
        if (map_chg || avoid_reserve) {
                gbl_chg = hugepage_subpool_get_pages(spool, 1);
                if (gbl_chg < 0) {
                        vma_end_reservation(h, vma, addr);
                        return ERR_PTR(-ENOSPC);
                }

                /*
                 * Even though there was no reservation in the region/reserve
                 * map, there could be reservations associated with the
                 * subpool that can be used.  This would be indicated if the
                 * return value of hugepage_subpool_get_pages() is zero.
                 * However, if avoid_reserve is specified we still avoid even
                 * the subpool reservations.
                 */
                if (avoid_reserve)
                        gbl_chg = 1;
        }

        /* If this allocation is not consuming a reservation, charge it now.
         */
        deferred_reserve = map_chg || avoid_reserve;
        if (deferred_reserve) {
                ret = hugetlb_cgroup_charge_cgroup_rsvd(
                        idx, pages_per_huge_page(h), &h_cg);
                if (ret)
                        goto out_subpool_put;
        }

        ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
        if (ret)
                goto out_uncharge_cgroup_reservation;

        spin_lock_irq(&hugetlb_lock);
        /*
         * glb_chg is passed to indicate whether or not a page must be taken
         * from the global free pool (global change).  gbl_chg == 0 indicates
         * a reservation exists for the allocation.
         */
        page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
        if (!page) {
                spin_unlock_irq(&hugetlb_lock);
                page = alloc_buddy_huge_page_with_mpol(h, vma, addr);
                if (!page)
                        goto out_uncharge_cgroup;
                if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
                        SetHPageRestoreReserve(page);
                        h->resv_huge_pages--;
                }
                spin_lock_irq(&hugetlb_lock);
                list_add(&page->lru, &h->hugepage_activelist);
                /* Fall through */
        }
        hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page);
        /* If allocation is not consuming a reservation, also store the
         * hugetlb_cgroup pointer on the page.
         */
        if (deferred_reserve) {
                hugetlb_cgroup_commit_charge_rsvd(idx, pages_per_huge_page(h),
                                                  h_cg, page);
        }

        spin_unlock_irq(&hugetlb_lock);

        hugetlb_set_page_subpool(page, spool);

        map_commit = vma_commit_reservation(h, vma, addr);
        if (unlikely(map_chg > map_commit)) {
                /*
                 * The page was added to the reservation map between
                 * vma_needs_reservation and vma_commit_reservation.
                 * This indicates a race with hugetlb_reserve_pages.
                 * Adjust for the subpool count incremented above AND
                 * in hugetlb_reserve_pages for the same page.  Also,
                 * the reservation count added in hugetlb_reserve_pages
                 * no longer applies.
                 */
                long rsv_adjust;

                rsv_adjust = hugepage_subpool_put_pages(spool, 1);
                hugetlb_acct_memory(h, -rsv_adjust);
                if (deferred_reserve)
                        hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
                                        pages_per_huge_page(h), page);
        }
        return page;

out_uncharge_cgroup:
        hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
out_uncharge_cgroup_reservation:
        if (deferred_reserve)
                hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h),
                                                    h_cg);
out_subpool_put:
        if (map_chg || avoid_reserve)
                hugepage_subpool_put_pages(spool, 1);
        vma_end_reservation(h, vma, addr);
        return ERR_PTR(-ENOSPC);
}

int alloc_bootmem_huge_page(struct hstate *h, int nid)
        __attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
int __alloc_bootmem_huge_page(struct hstate *h, int nid)
{
        struct huge_bootmem_page *m = NULL; /* initialize for clang */
        int nr_nodes, node;

        if (nid != NUMA_NO_NODE && nid >= nr_online_nodes)
                return 0;
        /* do node specific alloc */
        if (nid != NUMA_NO_NODE) {
                m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
                                0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
                if (!m)
                        return 0;
                goto found;
        }
        /* allocate from next node when distributing huge pages */
        for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
                m = memblock_alloc_try_nid_raw(
                                huge_page_size(h), huge_page_size(h),
                                0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
                /*
                 * Use the beginning of the huge page to store the
                 * huge_bootmem_page struct (until gather_bootmem
                 * puts them into the mem_map).
                 */
                if (!m)
                        return 0;
                goto found;
        }

found:
        /* Put them into a private list first because mem_map is not up yet */
        INIT_LIST_HEAD(&m->list);
        list_add(&m->list, &huge_boot_pages);
        m->hstate = h;
        return 1;
}

/*
 * Put bootmem huge pages into the standard lists after mem_map is up.
 * Note: This only applies to gigantic (order > MAX_ORDER) pages.
 */
static void __init gather_bootmem_prealloc(void)
{
        struct huge_bootmem_page *m;

        list_for_each_entry(m, &huge_boot_pages, list) {
                struct page *page = virt_to_page(m);
                struct hstate *h = m->hstate;

                VM_BUG_ON(!hstate_is_gigantic(h));
                WARN_ON(page_count(page) != 1);
                if (prep_compound_gigantic_page(page, huge_page_order(h))) {
                        WARN_ON(PageReserved(page));
                        prep_new_huge_page(h, page, page_to_nid(page));
                        put_page(page); /* add to the hugepage allocator */
                } else {
                        /* VERY unlikely inflated ref count on a tail page */
                        free_gigantic_page(page, huge_page_order(h));
                }

                /*
                 * We need to restore the 'stolen' pages to totalram_pages
                 * in order to fix confusing memory reports from free(1) and
                 * other side-effects, like CommitLimit going negative.
                 */
                adjust_managed_page_count(page, pages_per_huge_page(h));
                cond_resched();
        }
}
static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
{
        unsigned long i;
        char buf[32];

        for (i = 0; i < h->max_huge_pages_node[nid]; ++i) {
                if (hstate_is_gigantic(h)) {
                        if (!alloc_bootmem_huge_page(h, nid))
                                break;
                } else {
                        struct page *page;
                        gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;

                        page = alloc_fresh_huge_page(h, gfp_mask, nid,
                                        &node_states[N_MEMORY], NULL);
                        if (!page)
                                break;
                        put_page(page); /* free it into the hugepage allocator */
                }
                cond_resched();
        }
        if (i == h->max_huge_pages_node[nid])
                return;

        string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
        pr_warn("HugeTLB: allocating %u of page size %s failed node%d.  Only allocated %lu hugepages.\n",
                h->max_huge_pages_node[nid], buf, nid, i);
        h->max_huge_pages -= (h->max_huge_pages_node[nid] - i);
        h->max_huge_pages_node[nid] = i;
}

static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
{
        unsigned long i;
        nodemask_t *node_alloc_noretry;
        bool node_specific_alloc = false;

        /* skip gigantic hugepages allocation if hugetlb_cma enabled */
        if (hstate_is_gigantic(h) && hugetlb_cma_size) {
                pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
                return;
        }

        /* do node specific alloc */
        for (i = 0; i < nr_online_nodes; i++) {
                if (h->max_huge_pages_node[i] > 0) {
                        hugetlb_hstate_alloc_pages_onenode(h, i);
                        node_specific_alloc = true;
                }
        }

        if (node_specific_alloc)
                return;

        /* below will do all node balanced alloc */
        if (!hstate_is_gigantic(h)) {
                /*
                 * Bit mask controlling how hard we retry per-node allocations.
                 * Ignore errors as lower level routines can deal with
                 * node_alloc_noretry == NULL.  If this kmalloc fails at boot
                 * time, we are likely in bigger trouble.
                 */
                node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
                                                GFP_KERNEL);
        } else {
                /* allocations done at boot time */
                node_alloc_noretry = NULL;
        }

        /* bit mask controlling how hard we retry per-node allocations */
        if (node_alloc_noretry)
                nodes_clear(*node_alloc_noretry);

        for (i = 0; i < h->max_huge_pages; ++i) {
                if (hstate_is_gigantic(h)) {
                        if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
                                break;
                } else if (!alloc_pool_huge_page(h,
                                         &node_states[N_MEMORY],
                                         node_alloc_noretry))
                        break;
                cond_resched();
        }
        if (i < h->max_huge_pages) {
                char buf[32];

                string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
                pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
                        h->max_huge_pages, buf, i);
                h->max_huge_pages = i;
        }
        kfree(node_alloc_noretry);
}

static void __init hugetlb_init_hstates(void)
{
        struct hstate *h, *h2;

        for_each_hstate(h) {
                if (minimum_order > huge_page_order(h))
                        minimum_order = huge_page_order(h);

                /* oversize hugepages were init'ed in early boot */
                if (!hstate_is_gigantic(h))
                        hugetlb_hstate_alloc_pages(h);

                /*
                 * Set demote order for each hstate.  Note that
                 * h->demote_order is initially 0.
                 * - We can not demote gigantic pages if runtime freeing
                 *   is not supported, so skip this.
                 * - If CMA allocation is possible, we can not demote
                 *   HUGETLB_PAGE_ORDER or smaller size pages.
                 */
                if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                        continue;
                if (hugetlb_cma_size && h->order <= HUGETLB_PAGE_ORDER)
                        continue;
                for_each_hstate(h2) {
                        if (h2 == h)
                                continue;
                        if (h2->order < h->order &&
                            h2->order > h->demote_order)
                                h->demote_order = h2->order;
                }
        }
        VM_BUG_ON(minimum_order == UINT_MAX);
}

static void __init report_hugepages(void)
{
        struct hstate *h;

        for_each_hstate(h) {
                char buf[32];

                string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
                pr_info("HugeTLB registered %s page size, pre-allocated %ld pages\n",
                        buf, h->free_huge_pages);
        }
}

#ifdef CONFIG_HIGHMEM
static void try_to_free_low(struct hstate *h, unsigned long count,
                                                nodemask_t *nodes_allowed)
{
        int i;
        LIST_HEAD(page_list);

        lockdep_assert_held(&hugetlb_lock);
        if (hstate_is_gigantic(h))
                return;

        /*
         * Collect pages to be freed on a list, and free after dropping lock
         */
        for_each_node_mask(i, *nodes_allowed) {
                struct page *page, *next;
                struct list_head *freel = &h->hugepage_freelists[i];
                list_for_each_entry_safe(page, next, freel, lru) {
                        if (count >= h->nr_huge_pages)
                                goto out;
                        if (PageHighMem(page))
                                continue;
                        remove_hugetlb_page(h, page, false);
                        list_add(&page->lru, &page_list);
                }
        }

out:
        spin_unlock_irq(&hugetlb_lock);
        update_and_free_pages_bulk(h, &page_list);
        spin_lock_irq(&hugetlb_lock);
}
#else
static inline void try_to_free_low(struct hstate *h, unsigned long count,
                                                nodemask_t *nodes_allowed)
{
}
#endif

/*
 * Increment or decrement surplus_huge_pages.  Keep node-specific counters
 * balanced by operating on them in a round-robin fashion.
 * Returns 1 if an adjustment was made.
 */
static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
                                int delta)
{
        int nr_nodes, node;

        lockdep_assert_held(&hugetlb_lock);
        VM_BUG_ON(delta != -1 && delta != 1);

        if (delta < 0) {
                for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
                        if (h->surplus_huge_pages_node[node])
                                goto found;
                }
        } else {
                for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
                        if (h->surplus_huge_pages_node[node] <
                                        h->nr_huge_pages_node[node])
                                goto found;
                }
        }
        return 0;

found:
        h->surplus_huge_pages += delta;
        h->surplus_huge_pages_node[node] += delta;
        return 1;
}

#define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
                              nodemask_t *nodes_allowed)
{
        unsigned long min_count, ret;
        struct page *page;
        LIST_HEAD(page_list);
        NODEMASK_ALLOC(nodemask_t, node_alloc_noretry, GFP_KERNEL);

        /*
         * Bit mask controlling how hard we retry per-node allocations.
         * If we can not allocate the bit mask, do not attempt to allocate
         * the requested huge pages.
         */
        if (node_alloc_noretry)
                nodes_clear(*node_alloc_noretry);
        else
                return -ENOMEM;

        /*
         * resize_lock mutex prevents concurrent adjustments to number of
         * pages in hstate via the proc/sysfs interfaces.
         */
        mutex_lock(&h->resize_lock);
        flush_free_hpage_work(h);
        spin_lock_irq(&hugetlb_lock);

        /*
         * Check for a node specific request.
         * Changing node specific huge page count may require a corresponding
         * change to the global count.  In any case, the passed node mask
         * (nodes_allowed) will restrict alloc/free to the specified node.
         */
        if (nid != NUMA_NO_NODE) {
                unsigned long old_count = count;

                count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
                /*
                 * User may have specified a large count value which caused the
                 * above calculation to overflow.  In this case, they wanted
                 * to allocate as many huge pages as possible.  Set count to
                 * largest possible value to align with their intention.
                 */
                if (count < old_count)
                        count = ULONG_MAX;
        }

        /*
         * Gigantic pages runtime allocation depend on the capability for large
         * page range allocation.
         * If the system does not provide this feature, return an error when
         * the user tries to allocate gigantic pages but let the user free the
         * boottime allocated gigantic pages.
         */
        if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
                if (count > persistent_huge_pages(h)) {
                        spin_unlock_irq(&hugetlb_lock);
                        mutex_unlock(&h->resize_lock);
                        NODEMASK_FREE(node_alloc_noretry);
                        return -EINVAL;
                }
                /* Fall through to decrease pool */
        }

        /*
         * Increase the pool size
         * First take pages out of surplus state.  Then make up the
         * remaining difference by allocating fresh huge pages.
         *
         * We might race with alloc_surplus_huge_page() here and be unable
         * to convert a surplus huge page to a normal huge page. That is
         * not critical, though, it just means the overall size of the
         * pool might be one hugepage larger than it needs to be, but
         * within all the constraints specified by the sysctls.
         */
        while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
                if (!adjust_pool_surplus(h, nodes_allowed, -1))
                        break;
        }

        while (count > persistent_huge_pages(h)) {
                /*
                 * If this allocation races such that we no longer need the
                 * page, free_huge_page will handle it by freeing the page
                 * and reducing the surplus.
                 */
                spin_unlock_irq(&hugetlb_lock);

                /* yield cpu to avoid soft lockup */
                cond_resched();

                ret = alloc_pool_huge_page(h, nodes_allowed,
                                                node_alloc_noretry);
                spin_lock_irq(&hugetlb_lock);
                if (!ret)
                        goto out;

                /* Bail for signals. Probably ctrl-c from user */
                if (signal_pending(current))
                        goto out;
        }

        /*
         * Decrease the pool size
         * First return free pages to the buddy allocator (being careful
         * to keep enough around to satisfy reservations).  Then place
         * pages into surplus state as needed so the pool will shrink
         * to the desired size as pages become free.
         *
         * By placing pages into the surplus state independent of the
         * overcommit value, we are allowing the surplus pool size to
         * exceed overcommit. There are few sane options here. Since
         * alloc_surplus_huge_page() is checking the global counter,
         * though, we'll note that we're not allowed to exceed surplus
         * and won't grow the pool anywhere else. Not until one of the
         * sysctls are changed, or the surplus pages go out of use.
         */
        min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
        min_count = max(count, min_count);
        try_to_free_low(h, min_count, nodes_allowed);

        /*
         * Collect pages to be removed on list without dropping lock
         */
        while (min_count < persistent_huge_pages(h)) {
                page = remove_pool_huge_page(h, nodes_allowed, 0);
                if (!page)
                        break;

                list_add(&page->lru, &page_list);
        }
        /* free the pages after dropping lock */
        spin_unlock_irq(&hugetlb_lock);
        update_and_free_pages_bulk(h, &page_list);
        flush_free_hpage_work(h);
        spin_lock_irq(&hugetlb_lock);

        while (count < persistent_huge_pages(h)) {
                if (!adjust_pool_surplus(h, nodes_allowed, 1))
                        break;
        }
out:
        h->max_huge_pages = persistent_huge_pages(h);
        spin_unlock_irq(&hugetlb_lock);
        mutex_unlock(&h->resize_lock);

        NODEMASK_FREE(node_alloc_noretry);

        return 0;
}

static int demote_free_huge_page(struct hstate *h, struct page *page)
{
        int i, nid = page_to_nid(page);
        struct hstate *target_hstate;
        int rc = 0;

        target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order);

        remove_hugetlb_page_for_demote(h, page, false);
        spin_unlock_irq(&hugetlb_lock);

        rc = alloc_huge_page_vmemmap(h, page);
        if (rc) {
                /* Allocation of vmemmmap failed, we can not demote page */
                spin_lock_irq(&hugetlb_lock);
                set_page_refcounted(page);
                add_hugetlb_page(h, page, false);
                return rc;
        }

        /*
         * Use destroy_compound_hugetlb_page_for_demote for all huge page
         * sizes as it will not ref count pages.
         */
        destroy_compound_hugetlb_page_for_demote(page, huge_page_order(h));

        /*
         * Taking target hstate mutex synchronizes with set_max_huge_pages.
         * Without the mutex, pages added to target hstate could be marked
         * as surplus.
         *
         * Note that we already hold h->resize_lock.  To prevent deadlock,
         * use the convention of always taking larger size hstate mutex first.
         */
        mutex_lock(&target_hstate->resize_lock);
        for (i = 0; i < pages_per_huge_page(h);
                                i += pages_per_huge_page(target_hstate)) {
                if (hstate_is_gigantic(target_hstate))
                        prep_compound_gigantic_page_for_demote(page + i,
                                                        target_hstate->order);
                else
                        prep_compound_page(page + i, target_hstate->order);
                set_page_private(page + i, 0);
                set_page_refcounted(page + i);
                prep_new_huge_page(target_hstate, page + i, nid);
                put_page(page + i);
        }
        mutex_unlock(&target_hstate->resize_lock);

        spin_lock_irq(&hugetlb_lock);

        /*
         * Not absolutely necessary, but for consistency update max_huge_pages
         * based on pool changes for the demoted page.
         */
        h->max_huge_pages--;
        target_hstate->max_huge_pages += pages_per_huge_page(h);

        return rc;
}

static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
        __must_hold(&hugetlb_lock)
{
        int nr_nodes, node;
        struct page *page;
        int rc = 0;

        lockdep_assert_held(&hugetlb_lock);

        /* We should never get here if no demote order */
        if (!h->demote_order) {
                pr_warn("HugeTLB: NULL demote order passed to demote_pool_huge_page.\n");
                return -EINVAL;         /* internal error */
        }

        for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
                if (!list_empty(&h->hugepage_freelists[node])) {
                        page = list_entry(h->hugepage_freelists[node].next,
                                        struct page, lru);
                        rc = demote_free_huge_page(h, page);
                        break;
                }
        }

        return rc;
}

#define HSTATE_ATTR_RO(_name) \
        static struct kobj_attribute _name##_attr = __ATTR_RO(_name)

#define HSTATE_ATTR_WO(_name) \
        static struct kobj_attribute _name##_attr = __ATTR_WO(_name)

#define HSTATE_ATTR(_name) \
        static struct kobj_attribute _name##_attr = \
                __ATTR(_name, 0644, _name##_show, _name##_store)

static struct kobject *hugepages_kobj;
static struct kobject *hstate_kobjs[HUGE_MAX_HSTATE];

static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp);

static struct hstate *kobj_to_hstate(struct kobject *kobj, int *nidp)
{
        int i;

        for (i = 0; i < HUGE_MAX_HSTATE; i++)
                if (hstate_kobjs[i] == kobj) {
                        if (nidp)
                                *nidp = NUMA_NO_NODE;
                        return &hstates[i];
                }

        return kobj_to_node_hstate(kobj, nidp);
}

static ssize_t nr_hugepages_show_common(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        struct hstate *h;
        unsigned long nr_huge_pages;
        int nid;

        h = kobj_to_hstate(kobj, &nid);
        if (nid == NUMA_NO_NODE)
                nr_huge_pages = h->nr_huge_pages;
        else
                nr_huge_pages = h->nr_huge_pages_node[nid];

        return sysfs_emit(buf, "%lu\n", nr_huge_pages);
}

static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
                                           struct hstate *h, int nid,
                                           unsigned long count, size_t len)
{
        int err;
        nodemask_t nodes_allowed, *n_mask;

        if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                return -EINVAL;

        if (nid == NUMA_NO_NODE) {
                /*
                 * global hstate attribute
                 */
                if (!(obey_mempolicy &&
                                init_nodemask_of_mempolicy(&nodes_allowed)))
                        n_mask = &node_states[N_MEMORY];
                else
                        n_mask = &nodes_allowed;
        } else {
                /*
                 * Node specific request.  count adjustment happens in
                 * set_max_huge_pages() after acquiring hugetlb_lock.
                 */
                init_nodemask_of_node(&nodes_allowed, nid);
                n_mask = &nodes_allowed;
        }

        err = set_max_huge_pages(h, count, nid, n_mask);

        return err ? err : len;
}

static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
                                         struct kobject *kobj, const char *buf,
                                         size_t len)
{
        struct hstate *h;
        unsigned long count;
        int nid;
        int err;

        err = kstrtoul(buf, 10, &count);
        if (err)
                return err;

        h = kobj_to_hstate(kobj, &nid);
        return __nr_hugepages_store_common(obey_mempolicy, h, nid, count, len);
}

static ssize_t nr_hugepages_show(struct kobject *kobj,
                                       struct kobj_attribute *attr, char *buf)
{
        return nr_hugepages_show_common(kobj, attr, buf);
}

static ssize_t nr_hugepages_store(struct kobject *kobj,
               struct kobj_attribute *attr, const char *buf, size_t len)
{
        return nr_hugepages_store_common(false, kobj, buf, len);
}
HSTATE_ATTR(nr_hugepages);

#ifdef CONFIG_NUMA

/*
 * hstate attribute for optionally mempolicy-based constraint on persistent
 * huge page alloc/free.
 */
static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
                                           struct kobj_attribute *attr,
                                           char *buf)
{
        return nr_hugepages_show_common(kobj, attr, buf);
}

static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
               struct kobj_attribute *attr, const char *buf, size_t len)
{
        return nr_hugepages_store_common(true, kobj, buf, len);
}
HSTATE_ATTR(nr_hugepages_mempolicy);
#endif


static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        struct hstate *h = kobj_to_hstate(kobj, NULL);
        return sysfs_emit(buf, "%lu\n", h->nr_overcommit_huge_pages);
}

static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t count)
{
        int err;
        unsigned long input;
        struct hstate *h = kobj_to_hstate(kobj, NULL);

        if (hstate_is_gigantic(h))
                return -EINVAL;

        err = kstrtoul(buf, 10, &input);
        if (err)
                return err;

        spin_lock_irq(&hugetlb_lock);
        h->nr_overcommit_huge_pages = input;
        spin_unlock_irq(&hugetlb_lock);

        return count;
}
HSTATE_ATTR(nr_overcommit_hugepages);

static ssize_t free_hugepages_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        struct hstate *h;
        unsigned long free_huge_pages;
        int nid;

        h = kobj_to_hstate(kobj, &nid);
        if (nid == NUMA_NO_NODE)
                free_huge_pages = h->free_huge_pages;
        else
                free_huge_pages = h->free_huge_pages_node[nid];

        return sysfs_emit(buf, "%lu\n", free_huge_pages);
}
HSTATE_ATTR_RO(free_hugepages);

static ssize_t resv_hugepages_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        struct hstate *h = kobj_to_hstate(kobj, NULL);
        return sysfs_emit(buf, "%lu\n", h->resv_huge_pages);
}
HSTATE_ATTR_RO(resv_hugepages);

static ssize_t surplus_hugepages_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        struct hstate *h;
        unsigned long surplus_huge_pages;
        int nid;

        h = kobj_to_hstate(kobj, &nid);
        if (nid == NUMA_NO_NODE)
                surplus_huge_pages = h->surplus_huge_pages;
        else
                surplus_huge_pages = h->surplus_huge_pages_node[nid];

        return sysfs_emit(buf, "%lu\n", surplus_huge_pages);
}
HSTATE_ATTR_RO(surplus_hugepages);

static ssize_t demote_store(struct kobject *kobj,
               struct kobj_attribute *attr, const char *buf, size_t len)
{
        unsigned long nr_demote;
        unsigned long nr_available;
        nodemask_t nodes_allowed, *n_mask;
        struct hstate *h;
        int err = 0;
        int nid;

        err = kstrtoul(buf, 10, &nr_demote);
        if (err)
                return err;
        h = kobj_to_hstate(kobj, &nid);

        if (nid != NUMA_NO_NODE) {
                init_nodemask_of_node(&nodes_allowed, nid);
                n_mask = &nodes_allowed;
        } else {
                n_mask = &node_states[N_MEMORY];
        }

        /* Synchronize with other sysfs operations modifying huge pages */
        mutex_lock(&h->resize_lock);
        spin_lock_irq(&hugetlb_lock);

        while (nr_demote) {
                /*
                 * Check for available pages to demote each time thorough the
                 * loop as demote_pool_huge_page will drop hugetlb_lock.
                 */
                if (nid != NUMA_NO_NODE)
                        nr_available = h->free_huge_pages_node[nid];
                else
                        nr_available = h->free_huge_pages;
                nr_available -= h->resv_huge_pages;
                if (!nr_available)
                        break;

                err = demote_pool_huge_page(h, n_mask);
                if (err)
                        break;

                nr_demote--;
        }

        spin_unlock_irq(&hugetlb_lock);
        mutex_unlock(&h->resize_lock);

        if (err)
                return err;
        return len;
}
HSTATE_ATTR_WO(demote);

static ssize_t demote_size_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        int nid;
        struct hstate *h = kobj_to_hstate(kobj, &nid);
        unsigned long demote_size = (PAGE_SIZE << h->demote_order) / SZ_1K;

        return sysfs_emit(buf, "%lukB\n", demote_size);
}

static ssize_t demote_size_store(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        const char *buf, size_t count)
{
        struct hstate *h, *demote_hstate;
        unsigned long demote_size;
        unsigned int demote_order;
        int nid;

        demote_size = (unsigned long)memparse(buf, NULL);

        demote_hstate = size_to_hstate(demote_size);
        if (!demote_hstate)
                return -EINVAL;
        demote_order = demote_hstate->order;
        if (demote_order < HUGETLB_PAGE_ORDER)
                return -EINVAL;

        /* demote order must be smaller than hstate order */
        h = kobj_to_hstate(kobj, &nid);
        if (demote_order >= h->order)
                return -EINVAL;

        /* resize_lock synchronizes access to demote size and writes */
        mutex_lock(&h->resize_lock);
        h->demote_order = demote_order;
        mutex_unlock(&h->resize_lock);

        return count;
}
HSTATE_ATTR(demote_size);

static struct attribute *hstate_attrs[] = {
        &nr_hugepages_attr.attr,
        &nr_overcommit_hugepages_attr.attr,
        &free_hugepages_attr.attr,
        &resv_hugepages_attr.attr,
        &surplus_hugepages_attr.attr,
#ifdef CONFIG_NUMA
        &nr_hugepages_mempolicy_attr.attr,
#endif
        NULL,
};

static const struct attribute_group hstate_attr_group = {
        .attrs = hstate_attrs,
};

static struct attribute *hstate_demote_attrs[] = {
        &demote_size_attr.attr,
        &demote_attr.attr,
        NULL,
};

static const struct attribute_group hstate_demote_attr_group = {
        .attrs = hstate_demote_attrs,
};

static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
                                    struct kobject **hstate_kobjs,
                                    const struct attribute_group *hstate_attr_group)
{
        int retval;
        int hi = hstate_index(h);

        hstate_kobjs[hi] = kobject_create_and_add(h->name, parent);
        if (!hstate_kobjs[hi])
                return -ENOMEM;

        retval = sysfs_create_group(hstate_kobjs[hi], hstate_attr_group);
        if (retval) {
                kobject_put(hstate_kobjs[hi]);
                hstate_kobjs[hi] = NULL;
        }

        if (h->demote_order) {
                if (sysfs_create_group(hstate_kobjs[hi],
                                        &hstate_demote_attr_group))
                        pr_warn("HugeTLB unable to create demote interfaces for %s\n", h->name);
        }

        return retval;
}

static void __init hugetlb_sysfs_init(void)
{
        struct hstate *h;
        int err;

        hugepages_kobj = kobject_create_and_add("hugepages", mm_kobj);
        if (!hugepages_kobj)
                return;

        for_each_hstate(h) {
                err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
                                         hstate_kobjs, &hstate_attr_group);
                if (err)
                        pr_err("HugeTLB: Unable to add hstate %s", h->name);
        }
}

#ifdef CONFIG_NUMA

/*
 * node_hstate/s - associate per node hstate attributes, via their kobjects,
 * with node devices in node_devices[] using a parallel array.  The array
 * index of a node device or _hstate == node id.
 * This is here to avoid any static dependency of the node device driver, in
 * the base kernel, on the hugetlb module.
 */
struct node_hstate {
        struct kobject          *hugepages_kobj;
        struct kobject          *hstate_kobjs[HUGE_MAX_HSTATE];
};
static struct node_hstate node_hstates[MAX_NUMNODES];

/*
 * A subset of global hstate attributes for node devices
 */
static struct attribute *per_node_hstate_attrs[] = {
        &nr_hugepages_attr.attr,
        &free_hugepages_attr.attr,
        &surplus_hugepages_attr.attr,
        NULL,
};

static const struct attribute_group per_node_hstate_attr_group = {
        .attrs = per_node_hstate_attrs,
};

/*
 * kobj_to_node_hstate - lookup global hstate for node device hstate attr kobj.
 * Returns node id via non-NULL nidp.
 */
static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
{
        int nid;

        for (nid = 0; nid < nr_node_ids; nid++) {
                struct node_hstate *nhs = &node_hstates[nid];
                int i;
                for (i = 0; i < HUGE_MAX_HSTATE; i++)
                        if (nhs->hstate_kobjs[i] == kobj) {
                                if (nidp)
                                        *nidp = nid;
                                return &hstates[i];
                        }
        }

        BUG();
        return NULL;
}

/*
 * Unregister hstate attributes from a single node device.
 * No-op if no hstate attributes attached.
 */
static void hugetlb_unregister_node(struct node *node)
{
        struct hstate *h;
        struct node_hstate *nhs = &node_hstates[node->dev.id];

        if (!nhs->hugepages_kobj)
                return;         /* no hstate attributes */

        for_each_hstate(h) {
                int idx = hstate_index(h);
                if (nhs->hstate_kobjs[idx]) {
                        kobject_put(nhs->hstate_kobjs[idx]);
                        nhs->hstate_kobjs[idx] = NULL;
                }
        }

        kobject_put(nhs->hugepages_kobj);
        nhs->hugepages_kobj = NULL;
}


/*
 * Register hstate attributes for a single node device.
 * No-op if attributes already registered.
 */
static void hugetlb_register_node(struct node *node)
{
        struct hstate *h;
        struct node_hstate *nhs = &node_hstates[node->dev.id];
        int err;

        if (nhs->hugepages_kobj)
                return;         /* already allocated */

        nhs->hugepages_kobj = kobject_create_and_add("hugepages",
                                                        &node->dev.kobj);
        if (!nhs->hugepages_kobj)
                return;

        for_each_hstate(h) {
                err = hugetlb_sysfs_add_hstate(h, nhs->hugepages_kobj,
                                                nhs->hstate_kobjs,
                                                &per_node_hstate_attr_group);
                if (err) {
                        pr_err("HugeTLB: Unable to add hstate %s for node %d\n",
                                h->name, node->dev.id);
                        hugetlb_unregister_node(node);
                        break;
                }
        }
}

/*
 * hugetlb init time:  register hstate attributes for all registered node
 * devices of nodes that have memory.  All on-line nodes should have
 * registered their associated device by this time.
 */
static void __init hugetlb_register_all_nodes(void)
{
        int nid;

        for_each_node_state(nid, N_MEMORY) {
                struct node *node = node_devices[nid];
                if (node->dev.id == nid)
                        hugetlb_register_node(node);
        }

        /*
         * Let the node device driver know we're here so it can
         * [un]register hstate attributes on node hotplug.
         */
        register_hugetlbfs_with_node(hugetlb_register_node,
                                     hugetlb_unregister_node);
}
#else   /* !CONFIG_NUMA */

static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
{
        BUG();
        if (nidp)
                *nidp = -1;
        return NULL;
}