diff --git a/mm/hugetlb.c b/mm/hugetlb.c
new file mode 100644
index 0000000..309fb8c
--- /dev/null
+++ b/mm/hugetlb.c
@@ -0,0 +1,4949 @@
+/*
+ * 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/bootmem.h>
+#include <linux/sysfs.h>
+#include <linux/slab.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 <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/tlb.h>
+
+#include <linux/io.h>
+#include <linux/hugetlb.h>
+#include <linux/hugetlb_cgroup.h>
+#include <linux/node.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/page_owner.h>
+#include "internal.h"
+
+int hugetlb_max_hstate __read_mostly;
+unsigned int default_hstate_idx;
+struct hstate hstates[HUGE_MAX_HSTATE];
+/*
+ * 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 unsigned long __initdata default_hstate_size;
+static bool __initdata parsed_valid_hugepagesz = true;
+
+/*
+ * 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 void unlock_or_release_subpool(struct hugepage_subpool *spool)
+{
+	bool free = (spool->count == 0) && (spool->used_hpages == 0);
+
+	spin_unlock(&spool->lock);
+
+	/* If no pages are used, and no other handles to the subpool
+	 * remain, give up any reservations mased on minimum size and
+	 * free the subpool */
+	if (free) {
+		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)
+{
+	spin_lock(&spool->lock);
+	BUG_ON(!spool->count);
+	spool->count--;
+	unlock_or_release_subpool(spool);
+}
+
+/*
+ * Subpool accounting for allocating and reserving pages.
+ * Return -ENOMEM if there are not enough resources to satisfy the
+ * 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 manitained.
+ */
+static long hugepage_subpool_get_pages(struct hugepage_subpool *spool,
+				      long delta)
+{
+	long ret = delta;
+
+	if (!spool)
+		return ret;
+
+	spin_lock(&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(&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;
+
+	if (!spool)
+		return delta;
+
+	spin_lock(&spool->lock);
+
+	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);
+
+	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));
+}
+
+/*
+ * Region tracking -- allows tracking of reservations and instantiated pages
+ *                    across the pages in a mapping.
+ *
+ * The region data structures are embedded into a resv_map and protected
+ * by a resv_map's lock.  The set of regions within the resv_map represent
+ * reservations for huge pages, or huge pages that have already been
+ * instantiated within the map.  The from and to elements are huge page
+ * indicies into the associated mapping.  from indicates the starting index
+ * of the region.  to represents the first index past the end of  the region.
+ *
+ * For example, a file region structure with from == 0 and to == 4 represents
+ * four huge pages in a mapping.  It is important to note that the to element
+ * represents the first element past the end of the region. This is used in
+ * arithmetic as 4(to) - 0(from) = 4 huge pages in the region.
+ *
+ * Interval notation of the form [from, to) will be used to indicate that
+ * the endpoint from is inclusive and to is exclusive.
+ */
+struct file_region {
+	struct list_head link;
+	long from;
+	long to;
+};
+
+/*
+ * Add the huge page range represented by [f, t) to the reserve
+ * map.  In the normal case, existing regions will be expanded
+ * to accommodate the specified range.  Sufficient regions should
+ * exist for expansion due to the previous call to region_chg
+ * with the same range.  However, it is possible that region_del
+ * could have been called after region_chg and modifed the map
+ * in such a way that no region exists to be expanded.  In this
+ * case, pull a region descriptor from the cache associated with
+ * the map and use that for the new range.
+ *
+ * Return the number of new huge pages added to the map.  This
+ * number is greater than or equal to zero.
+ */
+static long region_add(struct resv_map *resv, long f, long t)
+{
+	struct list_head *head = &resv->regions;
+	struct file_region *rg, *nrg, *trg;
+	long add = 0;
+
+	spin_lock(&resv->lock);
+	/* Locate the region we are either in or before. */
+	list_for_each_entry(rg, head, link)
+		if (f <= rg->to)
+			break;
+
+	/*
+	 * If no region exists which can be expanded to include the
+	 * specified range, the list must have been modified by an
+	 * interleving call to region_del().  Pull a region descriptor
+	 * from the cache and use it for this range.
+	 */
+	if (&rg->link == head || t < rg->from) {
+		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 = f;
+		nrg->to = t;
+		list_add(&nrg->link, rg->link.prev);
+
+		add += t - f;
+		goto out_locked;
+	}
+
+	/* Round our left edge to the current segment if it encloses us. */
+	if (f > rg->from)
+		f = rg->from;
+
+	/* Check for and consume any regions we now overlap with. */
+	nrg = rg;
+	list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
+		if (&rg->link == head)
+			break;
+		if (rg->from > t)
+			break;
+
+		/* If this area reaches higher then extend our area to
+		 * include it completely.  If this is not the first area
+		 * which we intend to reuse, free it. */
+		if (rg->to > t)
+			t = rg->to;
+		if (rg != nrg) {
+			/* Decrement return value by the deleted range.
+			 * Another range will span this area so that by
+			 * end of routine add will be >= zero
+			 */
+			add -= (rg->to - rg->from);
+			list_del(&rg->link);
+			kfree(rg);
+		}
+	}
+
+	add += (nrg->from - f);		/* Added to beginning of region */
+	nrg->from = f;
+	add += t - nrg->to;		/* Added to end of region */
+	nrg->to = t;
+
+out_locked:
+	resv->adds_in_progress--;
+	spin_unlock(&resv->lock);
+	VM_BUG_ON(add < 0);
+	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.  However, if the existing regions in the map can not
+ * be expanded to represent the new range, a new file_region
+ * structure is added to the map as a placeholder.  This is
+ * so that the subsequent region_add call will have all the
+ * regions it needs and will not fail.
+ *
+ * Upon entry, region_chg will also examine the cache of region descriptors
+ * associated with the map.  If there are not enough descriptors cached, one
+ * will be allocated for the in progress add operation.
+ *
+ * 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)
+{
+	struct list_head *head = &resv->regions;
+	struct file_region *rg, *nrg = NULL;
+	long chg = 0;
+
+retry:
+	spin_lock(&resv->lock);
+retry_locked:
+	resv->adds_in_progress++;
+
+	/*
+	 * Check for sufficient descriptors in the cache to accommodate
+	 * the number of in progress add operations.
+	 */
+	if (resv->adds_in_progress > resv->region_cache_count) {
+		struct file_region *trg;
+
+		VM_BUG_ON(resv->adds_in_progress - resv->region_cache_count > 1);
+		/* Must drop lock to allocate a new descriptor. */
+		resv->adds_in_progress--;
+		spin_unlock(&resv->lock);
+
+		trg = kmalloc(sizeof(*trg), GFP_KERNEL);
+		if (!trg) {
+			kfree(nrg);
+			return -ENOMEM;
+		}
+
+		spin_lock(&resv->lock);
+		list_add(&trg->link, &resv->region_cache);
+		resv->region_cache_count++;
+		goto retry_locked;
+	}
+
+	/* Locate the region we are before or in. */
+	list_for_each_entry(rg, head, link)
+		if (f <= rg->to)
+			break;
+
+	/* If we are below the current region then a new region is required.
+	 * Subtle, allocate a new region at the position but make it zero
+	 * size such that we can guarantee to record the reservation. */
+	if (&rg->link == head || t < rg->from) {
+		if (!nrg) {
+			resv->adds_in_progress--;
+			spin_unlock(&resv->lock);
+			nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
+			if (!nrg)
+				return -ENOMEM;
+
+			nrg->from = f;
+			nrg->to   = f;
+			INIT_LIST_HEAD(&nrg->link);
+			goto retry;
+		}
+
+		list_add(&nrg->link, rg->link.prev);
+		chg = t - f;
+		goto out_nrg;
+	}
+
+	/* Round our left edge to the current segment if it encloses us. */
+	if (f > rg->from)
+		f = rg->from;
+	chg = t - f;
+
+	/* Check for and consume any regions we now overlap with. */
+	list_for_each_entry(rg, rg->link.prev, link) {
+		if (&rg->link == head)
+			break;
+		if (rg->from > t)
+			goto out;
+
+		/* We overlap with this area, if it extends further than
+		 * us then we must extend ourselves.  Account for its
+		 * existing reservation. */
+		if (rg->to > t) {
+			chg += rg->to - t;
+			t = rg->to;
+		}
+		chg -= rg->to - rg->from;
+	}
+
+out:
+	spin_unlock(&resv->lock);
+	/*  We already know we raced and no longer need the new region */
+	kfree(nrg);
+	return chg;
+out_nrg:
+	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.
+ *
+ * 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)
+{
+	spin_lock(&resv->lock);
+	VM_BUG_ON(!resv->region_cache_count);
+	resv->adds_in_progress--;
+	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;
+
+			/* New entry for end of split region */
+			nrg->from = t;
+			nrg->to = rg->to;
+			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;
+			list_del(&rg->link);
+			kfree(rg);
+			continue;
+		}
+
+		if (f <= rg->from) {	/* Trim beginning of region */
+			del += t - rg->from;
+			rg->from = t;
+		} else {		/* Trim end of region */
+			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;
+
+	rsv_adjust = hugepage_subpool_get_pages(spool, 1);
+	if (rsv_adjust) {
+		struct hstate *h = hstate_inode(inode);
+
+		hugetlb_acct_memory(h, 1);
+	}
+}
+
+/*
+ * 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;
+}
+
+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;
+
+	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)
+{
+	return inode->i_mapping->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;
+}
+
+/* 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 reverves 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);
+	list_move(&page->lru, &h->hugepage_freelists[nid]);
+	h->free_huge_pages++;
+	h->free_huge_pages_node[nid]++;
+}
+
+static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
+{
+	struct page *page;
+
+	list_for_each_entry(page, &h->hugepage_freelists[nid], lru)
+		if (!PageHWPoison(page))
+			break;
+	/*
+	 * if 'non-isolated free hugepage' not found on the list,
+	 * the allocation fails.
+	 */
+	if (&h->hugepage_freelists[nid] == &page->lru)
+		return NULL;
+	list_move(&page->lru, &h->hugepage_activelist);
+	set_page_refcounted(page);
+	h->free_huge_pages--;
+	h->free_huge_pages_node[nid]--;
+	return page;
+}
+
+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 = -1;
+
+	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;
+}
+
+/* Movability of hugepages depends on migration support. */
+static inline gfp_t htlb_alloc_mask(struct hstate *h)
+{
+	if (hugepage_migration_supported(h))
+		return GFP_HIGHUSER_MOVABLE;
+	else
+		return GFP_HIGHUSER;
+}
+
+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;
+	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);
+	page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
+	if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
+		SetPagePrivate(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 free_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--)
+
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
+static void destroy_compound_gigantic_page(struct page *page,
+					unsigned int order)
+{
+	int i;
+	int nr_pages = 1 << order;
+	struct page *p = page + 1;
+
+	atomic_set(compound_mapcount_ptr(page), 0);
+	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
+		clear_compound_head(p);
+		set_page_refcounted(p);
+	}
+
+	set_compound_order(page, 0);
+	__ClearPageHead(page);
+}
+
+static void free_gigantic_page(struct page *page, unsigned int order)
+{
+	free_contig_range(page_to_pfn(page), 1 << order);
+}
+
+static int __alloc_gigantic_page(unsigned long start_pfn,
+				unsigned long nr_pages, gfp_t gfp_mask)
+{
+	unsigned long end_pfn = start_pfn + nr_pages;
+	return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
+				  gfp_mask);
+}
+
+static bool pfn_range_valid_gigantic(struct zone *z,
+			unsigned long start_pfn, unsigned long nr_pages)
+{
+	unsigned long i, end_pfn = start_pfn + nr_pages;
+	struct page *page;
+
+	for (i = start_pfn; i < end_pfn; i++) {
+		if (!pfn_valid(i))
+			return false;
+
+		page = pfn_to_page(i);
+
+		if (page_zone(page) != z)
+			return false;
+
+		if (PageReserved(page))
+			return false;
+
+		if (page_count(page) > 0)
+			return false;
+
+		if (PageHuge(page))
+			return false;
+	}
+
+	return true;
+}
+
+static bool zone_spans_last_pfn(const struct zone *zone,
+			unsigned long start_pfn, unsigned long nr_pages)
+{
+	unsigned long last_pfn = start_pfn + nr_pages - 1;
+	return zone_spans_pfn(zone, last_pfn);
+}
+
+static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
+		int nid, nodemask_t *nodemask)
+{
+	unsigned int order = huge_page_order(h);
+	unsigned long nr_pages = 1 << order;
+	unsigned long ret, pfn, flags;
+	struct zonelist *zonelist;
+	struct zone *zone;
+	struct zoneref *z;
+
+	zonelist = node_zonelist(nid, gfp_mask);
+	for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nodemask) {
+		spin_lock_irqsave(&zone->lock, flags);
+
+		pfn = ALIGN(zone->zone_start_pfn, nr_pages);
+		while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
+			if (pfn_range_valid_gigantic(zone, pfn, nr_pages)) {
+				/*
+				 * We release the zone lock here because
+				 * alloc_contig_range() will also lock the zone
+				 * at some point. If there's an allocation
+				 * spinning on this lock, it may win the race
+				 * and cause alloc_contig_range() to fail...
+				 */
+				spin_unlock_irqrestore(&zone->lock, flags);
+				ret = __alloc_gigantic_page(pfn, nr_pages, gfp_mask);
+				if (!ret)
+					return pfn_to_page(pfn);
+				spin_lock_irqsave(&zone->lock, flags);
+			}
+			pfn += nr_pages;
+		}
+
+		spin_unlock_irqrestore(&zone->lock, flags);
+	}
+
+	return NULL;
+}
+
+static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
+static void prep_compound_gigantic_page(struct page *page, unsigned int order);
+
+#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
+static inline bool gigantic_page_supported(void) { return false; }
+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
+
+static void update_and_free_page(struct hstate *h, struct page *page)
+{
+	int i;
+
+	if (hstate_is_gigantic(h) && !gigantic_page_supported())
+		return;
+
+	h->nr_huge_pages--;
+	h->nr_huge_pages_node[page_to_nid(page)]--;
+	for (i = 0; i < pages_per_huge_page(h); i++) {
+		page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
+				1 << PG_referenced | 1 << PG_dirty |
+				1 << PG_active | 1 << PG_private |
+				1 << PG_writeback);
+	}
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
+	set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
+	set_page_refcounted(page);
+	if (hstate_is_gigantic(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));
+	}
+}
+
+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;
+}
+
+/*
+ * Test to determine whether the hugepage is "active/in-use" (i.e. being linked
+ * to hstate->hugepage_activelist.)
+ *
+ * This function can be called for tail pages, but never returns true for them.
+ */
+bool page_huge_active(struct page *page)
+{
+	VM_BUG_ON_PAGE(!PageHuge(page), page);
+	return PageHead(page) && PagePrivate(&page[1]);
+}
+
+/* never called for tail page */
+static void set_page_huge_active(struct page *page)
+{
+	VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
+	SetPagePrivate(&page[1]);
+}
+
+static void clear_page_huge_active(struct page *page)
+{
+	VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
+	ClearPagePrivate(&page[1]);
+}
+
+/*
+ * Internal hugetlb specific page flag. Do not use outside of the hugetlb
+ * code
+ */
+static inline bool PageHugeTemporary(struct page *page)
+{
+	if (!PageHuge(page))
+		return false;
+
+	return (unsigned long)page[2].mapping == -1U;
+}
+
+static inline void SetPageHugeTemporary(struct page *page)
+{
+	page[2].mapping = (void *)-1U;
+}
+
+static inline void ClearPageHugeTemporary(struct page *page)
+{
+	page[2].mapping = 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 =
+		(struct hugepage_subpool *)page_private(page);
+	bool restore_reserve;
+
+	set_page_private(page, 0);
+	page->mapping = NULL;
+	VM_BUG_ON_PAGE(page_count(page), page);
+	VM_BUG_ON_PAGE(page_mapcount(page), page);
+	restore_reserve = PagePrivate(page);
+	ClearPagePrivate(page);
+
+	/*
+	 * 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(&hugetlb_lock);
+	clear_page_huge_active(page);
+	hugetlb_cgroup_uncharge_page(hstate_index(h),
+				     pages_per_huge_page(h), page);
+	if (restore_reserve)
+		h->resv_huge_pages++;
+
+	if (PageHugeTemporary(page)) {
+		list_del(&page->lru);
+		ClearPageHugeTemporary(page);
+		update_and_free_page(h, page);
+	} else if (h->surplus_huge_pages_node[nid]) {
+		/* remove the page from active list */
+		list_del(&page->lru);
+		update_and_free_page(h, page);
+		h->surplus_huge_pages--;
+		h->surplus_huge_pages_node[nid]--;
+	} else {
+		arch_clear_hugepage_flags(page);
+		enqueue_huge_page(h, page);
+	}
+	spin_unlock(&hugetlb_lock);
+}
+
+static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
+{
+	INIT_LIST_HEAD(&page->lru);
+	set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
+	spin_lock(&hugetlb_lock);
+	set_hugetlb_cgroup(page, NULL);
+	h->nr_huge_pages++;
+	h->nr_huge_pages_node[nid]++;
+	spin_unlock(&hugetlb_lock);
+}
+
+static void prep_compound_gigantic_page(struct page *page, unsigned int order)
+{
+	int i;
+	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.  Otherwse 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);
+		set_page_count(p, 0);
+		set_compound_head(p, page);
+	}
+	atomic_set(compound_mapcount_ptr(page), -1);
+}
+
+/*
+ * 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 get_compound_page_dtor(page_head) == free_huge_page;
+}
+
+pgoff_t __basepage_index(struct page *page)
+{
+	struct page *page_head = compound_head(page);
+	pgoff_t index = page_index(page_head);
+	unsigned long compound_idx;
+
+	if (!PageHuge(page_head))
+		return page_index(page);
+
+	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)
+{
+	int order = huge_page_order(h);
+	struct page *page;
+
+	gfp_mask |= __GFP_COMP|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
+	if (nid == NUMA_NO_NODE)
+		nid = numa_mem_id();
+	page = __alloc_pages_nodemask(gfp_mask, order, nid, nmask);
+	if (page)
+		__count_vm_event(HTLB_BUDDY_PGALLOC);
+	else
+		__count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
+
+	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)
+{
+	struct page *page;
+
+	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);
+	if (!page)
+		return NULL;
+
+	if (hstate_is_gigantic(h))
+		prep_compound_gigantic_page(page, huge_page_order(h));
+	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)
+{
+	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);
+		if (page)
+			break;
+	}
+
+	if (!page)
+		return 0;
+
+	put_page(page); /* free it into the hugepage allocator */
+
+	return 1;
+}
+
+/*
+ * Free huge page from pool from next node to free.
+ * Attempt to keep persistent huge pages more or less
+ * balanced over allowed nodes.
+ * Called with hugetlb_lock locked.
+ */
+static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
+							 bool acct_surplus)
+{
+	int nr_nodes, node;
+	int ret = 0;
+
+	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])) {
+			struct page *page =
+				list_entry(h->hugepage_freelists[node].next,
+					  struct page, lru);
+			list_del(&page->lru);
+			h->free_huge_pages--;
+			h->free_huge_pages_node[node]--;
+			if (acct_surplus) {
+				h->surplus_huge_pages--;
+				h->surplus_huge_pages_node[node]--;
+			}
+			update_and_free_page(h, page);
+			ret = 1;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * Dissolve a given free hugepage into free buddy pages. This function does
+ * nothing for in-use (including surplus) hugepages. Returns -EBUSY if the
+ * dissolution fails because a give page is not a free hugepage, or because
+ * free hugepages are fully reserved.
+ */
+int dissolve_free_huge_page(struct page *page)
+{
+	int rc = -EBUSY;
+
+	spin_lock(&hugetlb_lock);
+	if (PageHuge(page) && !page_count(page)) {
+		struct page *head = compound_head(page);
+		struct hstate *h = page_hstate(head);
+		int nid = page_to_nid(head);
+		if (h->free_huge_pages - h->resv_huge_pages == 0)
+			goto out;
+		/*
+		 * 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);
+		}
+		list_del(&head->lru);
+		h->free_huge_pages--;
+		h->free_huge_pages_node[nid]--;
+		h->max_huge_pages--;
+		update_and_free_page(h, head);
+		rc = 0;
+	}
+out:
+	spin_unlock(&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);
+		if (PageHuge(page) && !page_count(page)) {
+			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)
+{
+	struct page *page = NULL;
+
+	if (hstate_is_gigantic(h))
+		return NULL;
+
+	spin_lock(&hugetlb_lock);
+	if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages)
+		goto out_unlock;
+	spin_unlock(&hugetlb_lock);
+
+	page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask);
+	if (!page)
+		return NULL;
+
+	spin_lock(&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) {
+		SetPageHugeTemporary(page);
+		put_page(page);
+		page = NULL;
+	} else {
+		h->surplus_huge_pages++;
+		h->surplus_huge_pages_node[page_to_nid(page)]++;
+	}
+
+out_unlock:
+	spin_unlock(&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);
+	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
+	 */
+	SetPageHugeTemporary(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;
+	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);
+	page = alloc_surplus_huge_page(h, gfp_mask, nid, nodemask);
+	mpol_cond_put(mpol);
+
+	return page;
+}
+
+/* page migration callback function */
+struct page *alloc_huge_page_node(struct hstate *h, int nid)
+{
+	gfp_t gfp_mask = htlb_alloc_mask(h);
+	struct page *page = NULL;
+
+	if (nid != NUMA_NO_NODE)
+		gfp_mask |= __GFP_THISNODE;
+
+	spin_lock(&hugetlb_lock);
+	if (h->free_huge_pages - h->resv_huge_pages > 0)
+		page = dequeue_huge_page_nodemask(h, gfp_mask, nid, NULL);
+	spin_unlock(&hugetlb_lock);
+
+	if (!page)
+		page = alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
+
+	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 = htlb_alloc_mask(h);
+
+	spin_lock(&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(&hugetlb_lock);
+			return page;
+		}
+	}
+	spin_unlock(&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);
+	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, int delta)
+{
+	struct list_head surplus_list;
+	struct page *page, *tmp;
+	int ret, i;
+	int needed, allocated;
+	bool alloc_ok = true;
+
+	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(&hugetlb_lock);
+	for (i = 0; i < needed; i++) {
+		page = alloc_surplus_huge_page(h, htlb_alloc_mask(h),
+				NUMA_NO_NODE, NULL);
+		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(&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;
+		/*
+		 * This page is now managed by the hugetlb allocator and has
+		 * no users -- drop the buddy allocator's reference.
+		 */
+		put_page_testzero(page);
+		VM_BUG_ON_PAGE(page_count(page), page);
+		enqueue_huge_page(h, page);
+	}
+free:
+	spin_unlock(&hugetlb_lock);
+
+	/* Free unnecessary surplus pages to the buddy allocator */
+	list_for_each_entry_safe(page, tmp, &surplus_list, lru)
+		put_page(page);
+	spin_lock(&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.
+ *
+ * Called with hugetlb_lock held.  However, the lock could be dropped (and
+ * reacquired) during calls to cond_resched_lock.  Whenever dropping the lock,
+ * we must make sure nobody else can claim pages we are in the process of
+ * freeing.  Do this by ensuring resv_huge_page always is greater than the
+ * number of huge pages we plan to free when dropping the lock.
+ */
+static void return_unused_surplus_pages(struct hstate *h,
+					unsigned long unused_resv_pages)
+{
+	unsigned long nr_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.
+	 * free_pool_huge_page() will balance the the freed pages across the
+	 * on-line nodes with memory and will handle the hstate accounting.
+	 *
+	 * Note that we decrement resv_huge_pages as we free the pages.  If
+	 * we drop the lock, resv_huge_pages will still be sufficiently large
+	 * to cover subsequent pages we may free.
+	 */
+	while (nr_pages--) {
+		h->resv_huge_pages--;
+		unused_resv_pages--;
+		if (!free_pool_huge_page(h, &node_states[N_MEMORY], 1))
+			goto out;
+		cond_resched_lock(&hugetlb_lock);
+	}
+
+out:
+	/* Fully uncommit the reservation */
+	h->resv_huge_pages -= unused_resv_pages;
+}
+
+
+/*
+ * 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.
+ */
+enum vma_resv_mode {
+	VMA_NEEDS_RESV,
+	VMA_COMMIT_RESV,
+	VMA_END_RESV,
+	VMA_ADD_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;
+
+	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);
+		break;
+	case VMA_COMMIT_RESV:
+		ret = region_add(resv, idx, idx + 1);
+		break;
+	case VMA_END_RESV:
+		region_abort(resv, idx, idx + 1);
+		ret = 0;
+		break;
+	case VMA_ADD_RESV:
+		if (vma->vm_flags & VM_MAYSHARE)
+			ret = region_add(resv, idx, idx + 1);
+		else {
+			region_abort(resv, idx, idx + 1);
+			ret = region_del(resv, idx, idx + 1);
+		}
+		break;
+	default:
+		BUG();
+	}
+
+	if (vma->vm_flags & VM_MAYSHARE)
+		return ret;
+	else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) && ret >= 0) {
+		/*
+		 * 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)
+			return 0;
+		else
+			return 1;
+	}
+	else
+		return ret < 0 ? ret : 0;
+}
+
+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);
+}
+
+/*
+ * This routine is called to restore a reservation on error paths.  In the
+ * specific error paths, a huge page was allocated (via alloc_huge_page)
+ * and is about to be freed.  If a reservation for the page existed,
+ * alloc_huge_page would have consumed the reservation and set PagePrivate
+ * in the newly allocated page.  When the page is freed via free_huge_page,
+ * the global reservation count will be incremented if PagePrivate is set.
+ * However, free_huge_page can not adjust the reserve map.  Adjust the
+ * reserve map here to be consistent with global reserve count adjustments
+ * to be made by free_huge_page.
+ */
+static void restore_reserve_on_error(struct hstate *h,
+			struct vm_area_struct *vma, unsigned long address,
+			struct page *page)
+{
+	if (unlikely(PagePrivate(page))) {
+		long rc = vma_needs_reservation(h, vma, address);
+
+		if (unlikely(rc < 0)) {
+			/*
+			 * Rare out of memory condition in reserve map
+			 * manipulation.  Clear PagePrivate 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.
+			 */
+			ClearPagePrivate(page);
+		} else if (rc) {
+			rc = vma_add_reservation(h, vma, address);
+			if (unlikely(rc < 0))
+				/*
+				 * See above comment about rare out of
+				 * memory condition.
+				 */
+				ClearPagePrivate(page);
+		} else
+			vma_end_reservation(h, vma, address);
+	}
+}
+
+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;
+
+	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;
+	}
+
+	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
+	if (ret)
+		goto out_subpool_put;
+
+	spin_lock(&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(&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)) {
+			SetPagePrivate(page);
+			h->resv_huge_pages--;
+		}
+		spin_lock(&hugetlb_lock);
+		list_move(&page->lru, &h->hugepage_activelist);
+		/* Fall through */
+	}
+	hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page);
+	spin_unlock(&hugetlb_lock);
+
+	set_page_private(page, (unsigned long)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);
+	}
+	return page;
+
+out_uncharge_cgroup:
+	hugetlb_cgroup_uncharge_cgroup(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)
+	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
+int __alloc_bootmem_huge_page(struct hstate *h)
+{
+	struct huge_bootmem_page *m;
+	int nr_nodes, node;
+
+	for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
+		void *addr;
+
+		addr = memblock_virt_alloc_try_nid_raw(
+				huge_page_size(h), huge_page_size(h),
+				0, BOOTMEM_ALLOC_ACCESSIBLE, node);
+		if (addr) {
+			/*
+			 * Use the beginning of the huge page to store the
+			 * huge_bootmem_page struct (until gather_bootmem
+			 * puts them into the mem_map).
+			 */
+			m = addr;
+			goto found;
+		}
+	}
+	return 0;
+
+found:
+	BUG_ON(!IS_ALIGNED(virt_to_phys(m), huge_page_size(h)));
+	/* 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;
+}
+
+static void __init prep_compound_huge_page(struct page *page,
+		unsigned int order)
+{
+	if (unlikely(order > (MAX_ORDER - 1)))
+		prep_compound_gigantic_page(page, order);
+	else
+		prep_compound_page(page, order);
+}
+
+/* Put bootmem huge pages into the standard lists after mem_map is up */
+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;
+
+		WARN_ON(page_count(page) != 1);
+		prep_compound_huge_page(page, h->order);
+		WARN_ON(PageReserved(page));
+		prep_new_huge_page(h, page, page_to_nid(page));
+		put_page(page); /* free it into the hugepage allocator */
+
+		/*
+		 * If we had gigantic hugepages allocated at boot time, we need
+		 * to restore the 'stolen' pages to totalram_pages in order to
+		 * fix confusing memory reports from free(1) and another
+		 * side-effects, like CommitLimit going negative.
+		 */
+		if (hstate_is_gigantic(h))
+			adjust_managed_page_count(page, 1 << h->order);
+		cond_resched();
+	}
+}
+
+static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
+{
+	unsigned long i;
+
+	for (i = 0; i < h->max_huge_pages; ++i) {
+		if (hstate_is_gigantic(h)) {
+			if (!alloc_bootmem_huge_page(h))
+				break;
+		} else if (!alloc_pool_huge_page(h,
+					 &node_states[N_MEMORY]))
+			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;
+	}
+}
+
+static void __init hugetlb_init_hstates(void)
+{
+	struct hstate *h;
+
+	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);
+	}
+	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;
+
+	if (hstate_is_gigantic(h))
+		return;
+
+	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)
+				return;
+			if (PageHighMem(page))
+				continue;
+			list_del(&page->lru);
+			update_and_free_page(h, page);
+			h->free_huge_pages--;
+			h->free_huge_pages_node[page_to_nid(page)]--;
+		}
+	}
+}
+#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;
+
+	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 unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
+						nodemask_t *nodes_allowed)
+{
+	unsigned long min_count, ret;
+
+	if (hstate_is_gigantic(h) && !gigantic_page_supported())
+		return h->max_huge_pages;
+
+	/*
+	 * 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.
+	 */
+	spin_lock(&hugetlb_lock);
+	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(&hugetlb_lock);
+
+		/* yield cpu to avoid soft lockup */
+		cond_resched();
+
+		ret = alloc_pool_huge_page(h, nodes_allowed);
+		spin_lock(&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);
+	while (min_count < persistent_huge_pages(h)) {
+		if (!free_pool_huge_page(h, nodes_allowed, 0))
+			break;
+		cond_resched_lock(&hugetlb_lock);
+	}
+	while (count < persistent_huge_pages(h)) {
+		if (!adjust_pool_surplus(h, nodes_allowed, 1))
+			break;
+	}
+out:
+	ret = persistent_huge_pages(h);
+	spin_unlock(&hugetlb_lock);
+	return ret;
+}
+
+#define HSTATE_ATTR_RO(_name) \
+	static struct kobj_attribute _name##_attr = __ATTR_RO(_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 sprintf(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_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
+
+	if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (nid == NUMA_NO_NODE) {
+		/*
+		 * global hstate attribute
+		 */
+		if (!(obey_mempolicy &&
+				init_nodemask_of_mempolicy(nodes_allowed))) {
+			NODEMASK_FREE(nodes_allowed);
+			nodes_allowed = &node_states[N_MEMORY];
+		}
+	} else if (nodes_allowed) {
+		/*
+		 * per node hstate attribute: adjust count to global,
+		 * but restrict alloc/free to the specified node.
+		 */
+		count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
+		init_nodemask_of_node(nodes_allowed, nid);
+	} else
+		nodes_allowed = &node_states[N_MEMORY];
+
+	h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);
+
+	if (nodes_allowed != &node_states[N_MEMORY])
+		NODEMASK_FREE(nodes_allowed);
+
+	return len;
+out:
+	NODEMASK_FREE(nodes_allowed);
+	return err;
+}
+
+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 sprintf(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(&hugetlb_lock);
+	h->nr_overcommit_huge_pages = input;
+	spin_unlock(&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 sprintf(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 sprintf(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 sprintf(buf, "%lu\n", surplus_huge_pages);
+}
+HSTATE_ATTR_RO(surplus_hugepages);
+
+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 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]);
+
+	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;
+}
+
+static void hugetlb_register_all_nodes(void) { }
+
+#endif
+
+static int __init hugetlb_init(void)
+{
+	int i;
+
+	if (!hugepages_supported())
+		return 0;
+
+	if (!size_to_hstate(default_hstate_size)) {
+		if (default_hstate_size != 0) {
+			pr_err("HugeTLB: unsupported default_hugepagesz %lu. Reverting to %lu\n",
+			       default_hstate_size, HPAGE_SIZE);
+		}
+
+		default_hstate_size = HPAGE_SIZE;
+		if (!size_to_hstate(default_hstate_size))
+			hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
+	}
+	default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size));
+	if (default_hstate_max_huge_pages) {
+		if (!default_hstate.max_huge_pages)
+			default_hstate.max_huge_pages = default_hstate_max_huge_pages;
+	}
+
+	hugetlb_init_hstates();
+	gather_bootmem_prealloc();
+	report_hugepages();
+
+	hugetlb_sysfs_init();
+	hugetlb_register_all_nodes();
+	hugetlb_cgroup_file_init();
+
+#ifdef CONFIG_SMP
+	num_fault_mutexes = roundup_pow_of_two(8 * num_possible_cpus());
+#else
+	num_fault_mutexes = 1;
+#endif
+	hugetlb_fault_mutex_table =
+		kmalloc_array(num_fault_mutexes, sizeof(struct mutex),
+			      GFP_KERNEL);
+	BUG_ON(!hugetlb_fault_mutex_table);
+
+	for (i = 0; i < num_fault_mutexes; i++)
+		mutex_init(&hugetlb_fault_mutex_table[i]);
+	return 0;
+}
+subsys_initcall(hugetlb_init);
+
+/* Should be called on processing a hugepagesz=... option */
+void __init hugetlb_bad_size(void)
+{
+	parsed_valid_hugepagesz = false;
+}
+
+void __init hugetlb_add_hstate(unsigned int order)
+{
+	struct hstate *h;
+	unsigned long i;
+
+	if (size_to_hstate(PAGE_SIZE << order)) {
+		pr_warn("hugepagesz= specified twice, ignoring\n");
+		return;
+	}
+	BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
+	BUG_ON(order == 0);
+	h = &hstates[hugetlb_max_hstate++];
+	h->order = order;
+	h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);
+	h->nr_huge_pages = 0;
+	h->free_huge_pages = 0;
+	for (i = 0; i < MAX_NUMNODES; ++i)
+		INIT_LIST_HEAD(&h->hugepage_freelists[i]);
+	INIT_LIST_HEAD(&h->hugepage_activelist);
+	h->next_nid_to_alloc = first_memory_node;
+	h->next_nid_to_free = first_memory_node;
+	snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
+					huge_page_size(h)/1024);
+
+	parsed_hstate = h;
+}
+
+static int __init hugetlb_nrpages_setup(char *s)
+{
+	unsigned long *mhp;
+	static unsigned long *last_mhp;
+
+	if (!parsed_valid_hugepagesz) {
+		pr_warn("hugepages = %s preceded by "
+			"an unsupported hugepagesz, ignoring\n", s);
+		parsed_valid_hugepagesz = true;
+		return 1;
+	}
+	/*
+	 * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter yet,
+	 * so this hugepages= parameter goes to the "default hstate".
+	 */
+	else if (!hugetlb_max_hstate)
+		mhp = &default_hstate_max_huge_pages;
+	else
+		mhp = &parsed_hstate->max_huge_pages;
+
+	if (mhp == last_mhp) {
+		pr_warn("hugepages= specified twice without interleaving hugepagesz=, ignoring\n");
+		return 1;
+	}
+
+	if (sscanf(s, "%lu", mhp) <= 0)
+		*mhp = 0;
+
+	/*
+	 * Global state is always initialized later in hugetlb_init.
+	 * But we need to allocate >= MAX_ORDER hstates here early to still
+	 * use the bootmem allocator.
+	 */
+	if (hugetlb_max_hstate && parsed_hstate->order >= MAX_ORDER)
+		hugetlb_hstate_alloc_pages(parsed_hstate);
+
+	last_mhp = mhp;
+
+	return 1;
+}
+__setup("hugepages=", hugetlb_nrpages_setup);
+
+static int __init hugetlb_default_setup(char *s)
+{
+	default_hstate_size = memparse(s, &s);
+	return 1;
+}
+__setup("default_hugepagesz=", hugetlb_default_setup);
+
+static unsigned int cpuset_mems_nr(unsigned int *array)
+{
+	int node;
+	unsigned int nr = 0;
+
+	for_each_node_mask(node, cpuset_current_mems_allowed)
+		nr += array[node];
+
+	return nr;
+}
+
+#ifdef CONFIG_SYSCTL
+static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
+			 struct ctl_table *table, int write,
+			 void __user *buffer, size_t *length, loff_t *ppos)
+{
+	struct hstate *h = &default_hstate;
+	unsigned long tmp = h->max_huge_pages;
+	int ret;
+
+	if (!hugepages_supported())
+		return -EOPNOTSUPP;
+
+	table->data = &tmp;
+	table->maxlen = sizeof(unsigned long);
+	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
+	if (ret)
+		goto out;
+
+	if (write)
+		ret = __nr_hugepages_store_common(obey_mempolicy, h,
+						  NUMA_NO_NODE, tmp, *length);
+out:
+	return ret;
+}
+
+int hugetlb_sysctl_handler(struct ctl_table *table, int write,
+			  void __user *buffer, size_t *length, loff_t *ppos)
+{
+
+	return hugetlb_sysctl_handler_common(false, table, write,
+							buffer, length, ppos);
+}
+
+#ifdef CONFIG_NUMA
+int hugetlb_mempolicy_sysctl_handler(struct ctl_table *table, int write,
+			  void __user *buffer, size_t *length, loff_t *ppos)
+{
+	return hugetlb_sysctl_handler_common(true, table, write,
+							buffer, length, ppos);
+}
+#endif /* CONFIG_NUMA */
+
+int hugetlb_overcommit_handler(struct ctl_table *table, int write,
+			void __user *buffer,
+			size_t *length, loff_t *ppos)
+{
+	struct hstate *h = &default_hstate;
+	unsigned long tmp;
+	int ret;
+
+	if (!hugepages_supported())
+		return -EOPNOTSUPP;
+
+	tmp = h->nr_overcommit_huge_pages;
+
+	if (write && hstate_is_gigantic(h))
+		return -EINVAL;
+
+	table->data = &tmp;
+	table->maxlen = sizeof(unsigned long);
+	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
+	if (ret)
+		goto out;
+
+	if (write) {
+		spin_lock(&hugetlb_lock);
+		h->nr_overcommit_huge_pages = tmp;
+		spin_unlock(&hugetlb_lock);
+	}
+out:
+	return ret;
+}
+
+#endif /* CONFIG_SYSCTL */
+
+void hugetlb_report_meminfo(struct seq_file *m)
+{
+	struct hstate *h;
+	unsigned long total = 0;
+
+	if (!hugepages_supported())
+		return;
+
+	for_each_hstate(h) {
+		unsigned long count = h->nr_huge_pages;
+
+		total += (PAGE_SIZE << huge_page_order(h)) * count;
+
+		if (h == &default_hstate)
+			seq_printf(m,
+				   "HugePages_Total:   %5lu\n"
+				   "HugePages_Free:    %5lu\n"
+				   "HugePages_Rsvd:    %5lu\n"
+				   "HugePages_Surp:    %5lu\n"
+				   "Hugepagesize:   %8lu kB\n",
+				   count,
+				   h->free_huge_pages,
+				   h->resv_huge_pages,
+				   h->surplus_huge_pages,
+				   (PAGE_SIZE << huge_page_order(h)) / 1024);
+	}
+
+	seq_printf(m, "Hugetlb:        %8lu kB\n", total / 1024);
+}
+
+int hugetlb_report_node_meminfo(int nid, char *buf)
+{
+	struct hstate *h = &default_hstate;
+	if (!hugepages_supported())
+		return 0;
+	return sprintf(buf,
+		"Node %d HugePages_Total: %5u\n"
+		"Node %d HugePages_Free:  %5u\n"
+		"Node %d HugePages_Surp:  %5u\n",
+		nid, h->nr_huge_pages_node[nid],
+		nid, h->free_huge_pages_node[nid],
+		nid, h->surplus_huge_pages_node[nid]);
+}
+
+void hugetlb_show_meminfo(void)
+{
+	struct hstate *h;
+	int nid;
+
+	if (!hugepages_supported())
+		return;
+
+	for_each_node_state(nid, N_MEMORY)
+		for_each_hstate(h)
+			pr_info("Node %d hugepages_total=%u hugepages_free=%u hugepages_surp=%u hugepages_size=%lukB\n",
+				nid,
+				h->nr_huge_pages_node[nid],
+				h->free_huge_pages_node[nid],
+				h->surplus_huge_pages_node[nid],
+				1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+}
+
+void hugetlb_report_usage(struct seq_file *m, struct mm_struct *mm)
+{
+	seq_printf(m, "HugetlbPages:\t%8lu kB\n",
+		   atomic_long_read(&mm->hugetlb_usage) << (PAGE_SHIFT - 10));
+}
+
+/* Return the number pages of memory we physically have, in PAGE_SIZE units. */
+unsigned long hugetlb_total_pages(void)
+{
+	struct hstate *h;
+	unsigned long nr_total_pages = 0;
+
+	for_each_hstate(h)
+		nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
+	return nr_total_pages;
+}
+
+static int hugetlb_acct_memory(struct hstate *h, long delta)
+{
+	int ret = -ENOMEM;
+
+	spin_lock(&hugetlb_lock);
+	/*
+	 * When cpuset is configured, it breaks the strict hugetlb page
+	 * reservation as the accounting is done on a global variable. Such
+	 * reservation is completely rubbish in the presence of cpuset because
+	 * the reservation is not checked against page availability for the
+	 * current cpuset. Application can still potentially OOM'ed by kernel
+	 * with lack of free htlb page in cpuset that the task is in.
+	 * Attempt to enforce strict accounting with cpuset is almost
+	 * impossible (or too ugly) because cpuset is too fluid that
+	 * task or memory node can be dynamically moved between cpusets.
+	 *
+	 * The change of semantics for shared hugetlb mapping with cpuset is
+	 * undesirable. However, in order to preserve some of the semantics,
+	 * we fall back to check against current free page availability as
+	 * a best attempt and hopefully to minimize the impact of changing
+	 * semantics that cpuset has.
+	 */
+	if (delta > 0) {
+		if (gather_surplus_pages(h, delta) < 0)
+			goto out;
+
+		if (delta > cpuset_mems_nr(h->free_huge_pages_node)) {
+			return_unused_surplus_pages(h, delta);
+			goto out;
+		}
+	}
+
+	ret = 0;
+	if (delta < 0)
+		return_unused_surplus_pages(h, (unsigned long) -delta);
+
+out:
+	spin_unlock(&hugetlb_lock);
+	return ret;
+}
+
+static void hugetlb_vm_op_open(struct vm_area_struct *vma)
+{
+	struct resv_map *resv = vma_resv_map(vma);
+
+	/*
+	 * This new VMA should share its siblings reservation map if present.
+	 * The VMA will only ever have a valid reservation map pointer where
+	 * it is being copied for another still existing VMA.  As that VMA
+	 * has a reference to the reservation map it cannot disappear until
+	 * after this open call completes.  It is therefore safe to take a
+	 * new reference here without additional locking.
+	 */
+	if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
+		kref_get(&resv->refs);
+}
+
+static void hugetlb_vm_op_close(struct vm_area_struct *vma)
+{
+	struct hstate *h = hstate_vma(vma);
+	struct resv_map *resv = vma_resv_map(vma);
+	struct hugepage_subpool *spool = subpool_vma(vma);
+	unsigned long reserve, start, end;
+	long gbl_reserve;
+
+	if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER))
+		return;
+
+	start = vma_hugecache_offset(h, vma, vma->vm_start);
+	end = vma_hugecache_offset(h, vma, vma->vm_end);
+
+	reserve = (end - start) - region_count(resv, start, end);
+
+	kref_put(&resv->refs, resv_map_release);
+
+	if (reserve) {
+		/*
+		 * Decrement reserve counts.  The global reserve count may be
+		 * adjusted if the subpool has a minimum size.
+		 */
+		gbl_reserve = hugepage_subpool_put_pages(spool, reserve);
+		hugetlb_acct_memory(h, -gbl_reserve);
+	}
+}
+
+static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (addr & ~(huge_page_mask(hstate_vma(vma))))
+		return -EINVAL;
+	return 0;
+}
+
+static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
+{
+	struct hstate *hstate = hstate_vma(vma);
+
+	return 1UL << huge_page_shift(hstate);
+}
+
+/*
+ * We cannot handle pagefaults against hugetlb pages at all.  They cause
+ * handle_mm_fault() to try to instantiate regular-sized pages in the
+ * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
+ * this far.
+ */
+static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
+{
+	BUG();
+	return 0;
+}
+
+/*
+ * When a new function is introduced to vm_operations_struct and added
+ * to hugetlb_vm_ops, please consider adding the function to shm_vm_ops.
+ * This is because under System V memory model, mappings created via
+ * shmget/shmat with "huge page" specified are backed by hugetlbfs files,
+ * their original vm_ops are overwritten with shm_vm_ops.
+ */
+const struct vm_operations_struct hugetlb_vm_ops = {
+	.fault = hugetlb_vm_op_fault,
+	.open = hugetlb_vm_op_open,
+	.close = hugetlb_vm_op_close,
+	.split = hugetlb_vm_op_split,
+	.pagesize = hugetlb_vm_op_pagesize,
+};
+
+static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
+				int writable)
+{
+	pte_t entry;
+
+	if (writable) {
+		entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
+					 vma->vm_page_prot)));
+	} else {
+		entry = huge_pte_wrprotect(mk_huge_pte(page,
+					   vma->vm_page_prot));
+	}
+	entry = pte_mkyoung(entry);
+	entry = pte_mkhuge(entry);
+	entry = arch_make_huge_pte(entry, vma, page, writable);
+
+	return entry;
+}
+
+static void set_huge_ptep_writable(struct vm_area_struct *vma,
+				   unsigned long address, pte_t *ptep)
+{
+	pte_t entry;
+
+	entry = huge_pte_mkwrite(huge_pte_mkdirty(huge_ptep_get(ptep)));
+	if (huge_ptep_set_access_flags(vma, address, ptep, entry, 1))
+		update_mmu_cache(vma, address, ptep);
+}
+
+bool is_hugetlb_entry_migration(pte_t pte)
+{
+	swp_entry_t swp;
+
+	if (huge_pte_none(pte) || pte_present(pte))
+		return false;
+	swp = pte_to_swp_entry(pte);
+	if (non_swap_entry(swp) && is_migration_entry(swp))
+		return true;
+	else
+		return false;
+}
+
+static int is_hugetlb_entry_hwpoisoned(pte_t pte)
+{
+	swp_entry_t swp;
+
+	if (huge_pte_none(pte) || pte_present(pte))
+		return 0;
+	swp = pte_to_swp_entry(pte);
+	if (non_swap_entry(swp) && is_hwpoison_entry(swp))
+		return 1;
+	else
+		return 0;
+}
+
+int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
+			    struct vm_area_struct *vma)
+{
+	pte_t *src_pte, *dst_pte, entry, dst_entry;
+	struct page *ptepage;
+	unsigned long addr;
+	int cow;
+	struct hstate *h = hstate_vma(vma);
+	unsigned long sz = huge_page_size(h);
+	unsigned long mmun_start;	/* For mmu_notifiers */
+	unsigned long mmun_end;		/* For mmu_notifiers */
+	int ret = 0;
+
+	cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+
+	mmun_start = vma->vm_start;
+	mmun_end = vma->vm_end;
+	if (cow)
+		mmu_notifier_invalidate_range_start(src, mmun_start, mmun_end);
+
+	for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
+		spinlock_t *src_ptl, *dst_ptl;
+		src_pte = huge_pte_offset(src, addr, sz);
+		if (!src_pte)
+			continue;
+		dst_pte = huge_pte_alloc(dst, addr, sz);
+		if (!dst_pte) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		/*
+		 * If the pagetables are shared don't copy or take references.
+		 * dst_pte == src_pte is the common case of src/dest sharing.
+		 *
+		 * However, src could have 'unshared' and dst shares with
+		 * another vma.  If dst_pte !none, this implies sharing.
+		 * Check here before taking page table lock, and once again
+		 * after taking the lock below.
+		 */
+		dst_entry = huge_ptep_get(dst_pte);
+		if ((dst_pte == src_pte) || !huge_pte_none(dst_entry))
+			continue;
+
+		dst_ptl = huge_pte_lock(h, dst, dst_pte);
+		src_ptl = huge_pte_lockptr(h, src, src_pte);
+		spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+		entry = huge_ptep_get(src_pte);
+		dst_entry = huge_ptep_get(dst_pte);
+		if (huge_pte_none(entry) || !huge_pte_none(dst_entry)) {
+			/*
+			 * Skip if src entry none.  Also, skip in the
+			 * unlikely case dst entry !none as this implies
+			 * sharing with another vma.
+			 */
+			;
+		} else if (unlikely(is_hugetlb_entry_migration(entry) ||
+				    is_hugetlb_entry_hwpoisoned(entry))) {
+			swp_entry_t swp_entry = pte_to_swp_entry(entry);
+
+			if (is_write_migration_entry(swp_entry) && cow) {
+				/*
+				 * COW mappings require pages in both
+				 * parent and child to be set to read.
+				 */
+				make_migration_entry_read(&swp_entry);
+				entry = swp_entry_to_pte(swp_entry);
+				set_huge_swap_pte_at(src, addr, src_pte,
+						     entry, sz);
+			}
+			set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz);
+		} else {
+			if (cow) {
+				/*
+				 * No need to notify as we are downgrading page
+				 * table protection not changing it to point
+				 * to a new page.
+				 *
+				 * See Documentation/vm/mmu_notifier.rst
+				 */
+				huge_ptep_set_wrprotect(src, addr, src_pte);
+			}
+			entry = huge_ptep_get(src_pte);
+			ptepage = pte_page(entry);
+			get_page(ptepage);
+			page_dup_rmap(ptepage, true);
+			set_huge_pte_at(dst, addr, dst_pte, entry);
+			hugetlb_count_add(pages_per_huge_page(h), dst);
+		}
+		spin_unlock(src_ptl);
+		spin_unlock(dst_ptl);
+	}
+
+	if (cow)
+		mmu_notifier_invalidate_range_end(src, mmun_start, mmun_end);
+
+	return ret;
+}
+
+void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
+			    unsigned long start, unsigned long end,
+			    struct page *ref_page)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	unsigned long address;
+	pte_t *ptep;
+	pte_t pte;
+	spinlock_t *ptl;
+	struct page *page;
+	struct hstate *h = hstate_vma(vma);
+	unsigned long sz = huge_page_size(h);
+	unsigned long mmun_start = start;	/* For mmu_notifiers */
+	unsigned long mmun_end   = end;		/* For mmu_notifiers */
+
+	WARN_ON(!is_vm_hugetlb_page(vma));
+	BUG_ON(start & ~huge_page_mask(h));
+	BUG_ON(end & ~huge_page_mask(h));
+
+	/*
+	 * This is a hugetlb vma, all the pte entries should point
+	 * to huge page.
+	 */
+	tlb_remove_check_page_size_change(tlb, sz);
+	tlb_start_vma(tlb, vma);
+
+	/*
+	 * If sharing possible, alert mmu notifiers of worst case.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &mmun_start, &mmun_end);
+	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
+	address = start;
+	for (; address < end; address += sz) {
+		ptep = huge_pte_offset(mm, address, sz);
+		if (!ptep)
+			continue;
+
+		ptl = huge_pte_lock(h, mm, ptep);
+		if (huge_pmd_unshare(mm, &address, ptep)) {
+			spin_unlock(ptl);
+			/*
+			 * We just unmapped a page of PMDs by clearing a PUD.
+			 * The caller's TLB flush range should cover this area.
+			 */
+			continue;
+		}
+
+		pte = huge_ptep_get(ptep);
+		if (huge_pte_none(pte)) {
+			spin_unlock(ptl);
+			continue;
+		}
+
+		/*
+		 * Migrating hugepage or HWPoisoned hugepage is already
+		 * unmapped and its refcount is dropped, so just clear pte here.
+		 */
+		if (unlikely(!pte_present(pte))) {
+			huge_pte_clear(mm, address, ptep, sz);
+			spin_unlock(ptl);
+			continue;
+		}
+
+		page = pte_page(pte);
+		/*
+		 * If a reference page is supplied, it is because a specific
+		 * page is being unmapped, not a range. Ensure the page we
+		 * are about to unmap is the actual page of interest.
+		 */
+		if (ref_page) {
+			if (page != ref_page) {
+				spin_unlock(ptl);
+				continue;
+			}
+			/*
+			 * Mark the VMA as having unmapped its page so that
+			 * future faults in this VMA will fail rather than
+			 * looking like data was lost
+			 */
+			set_vma_resv_flags(vma, HPAGE_RESV_UNMAPPED);
+		}
+
+		pte = huge_ptep_get_and_clear(mm, address, ptep);
+		tlb_remove_huge_tlb_entry(h, tlb, ptep, address);
+		if (huge_pte_dirty(pte))
+			set_page_dirty(page);
+
+		hugetlb_count_sub(pages_per_huge_page(h), mm);
+		page_remove_rmap(page, true);
+
+		spin_unlock(ptl);
+		tlb_remove_page_size(tlb, page, huge_page_size(h));
+		/*
+		 * Bail out after unmapping reference page if supplied
+		 */
+		if (ref_page)
+			break;
+	}
+	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
+	tlb_end_vma(tlb, vma);
+}
+
+void __unmap_hugepage_range_final(struct mmu_gather *tlb,
+			  struct vm_area_struct *vma, unsigned long start,
+			  unsigned long end, struct page *ref_page)
+{
+	__unmap_hugepage_range(tlb, vma, start, end, ref_page);
+
+	/*
+	 * Clear this flag so that x86's huge_pmd_share page_table_shareable
+	 * test will fail on a vma being torn down, and not grab a page table
+	 * on its way out.  We're lucky that the flag has such an appropriate
+	 * name, and can in fact be safely cleared here. We could clear it
+	 * before the __unmap_hugepage_range above, but all that's necessary
+	 * is to clear it before releasing the i_mmap_rwsem. This works
+	 * because in the context this is called, the VMA is about to be
+	 * destroyed and the i_mmap_rwsem is held.
+	 */
+	vma->vm_flags &= ~VM_MAYSHARE;
+}
+
+void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
+			  unsigned long end, struct page *ref_page)
+{
+	struct mm_struct *mm;
+	struct mmu_gather tlb;
+	unsigned long tlb_start = start;
+	unsigned long tlb_end = end;
+
+	/*
+	 * If shared PMDs were possibly used within this vma range, adjust
+	 * start/end for worst case tlb flushing.
+	 * Note that we can not be sure if PMDs are shared until we try to
+	 * unmap pages.  However, we want to make sure TLB flushing covers
+	 * the largest possible range.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &tlb_start, &tlb_end);
+
+	mm = vma->vm_mm;
+
+	tlb_gather_mmu(&tlb, mm, tlb_start, tlb_end);
+	__unmap_hugepage_range(&tlb, vma, start, end, ref_page);
+	tlb_finish_mmu(&tlb, tlb_start, tlb_end);
+}
+
+/*
+ * This is called when the original mapper is failing to COW a MAP_PRIVATE
+ * mappping it owns the reserve page for. The intention is to unmap the page
+ * from other VMAs and let the children be SIGKILLed if they are faulting the
+ * same region.
+ */
+static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
+			      struct page *page, unsigned long address)
+{
+	struct hstate *h = hstate_vma(vma);
+	struct vm_area_struct *iter_vma;
+	struct address_space *mapping;
+	pgoff_t pgoff;
+
+	/*
+	 * vm_pgoff is in PAGE_SIZE units, hence the different calculation
+	 * from page cache lookup which is in HPAGE_SIZE units.
+	 */
+	address = address & huge_page_mask(h);
+	pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) +
+			vma->vm_pgoff;
+	mapping = vma->vm_file->f_mapping;
+
+	/*
+	 * Take the mapping lock for the duration of the table walk. As
+	 * this mapping should be shared between all the VMAs,
+	 * __unmap_hugepage_range() is called as the lock is already held
+	 */
+	i_mmap_lock_write(mapping);
+	vma_interval_tree_foreach(iter_vma, &mapping->i_mmap, pgoff, pgoff) {
+		/* Do not unmap the current VMA */
+		if (iter_vma == vma)
+			continue;
+
+		/*
+		 * Shared VMAs have their own reserves and do not affect
+		 * MAP_PRIVATE accounting but it is possible that a shared
+		 * VMA is using the same page so check and skip such VMAs.
+		 */
+		if (iter_vma->vm_flags & VM_MAYSHARE)
+			continue;
+
+		/*
+		 * Unmap the page from other VMAs without their own reserves.
+		 * They get marked to be SIGKILLed if they fault in these
+		 * areas. This is because a future no-page fault on this VMA
+		 * could insert a zeroed page instead of the data existing
+		 * from the time of fork. This would look like data corruption
+		 */
+		if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
+			unmap_hugepage_range(iter_vma, address,
+					     address + huge_page_size(h), page);
+	}
+	i_mmap_unlock_write(mapping);
+}
+
+/*
+ * Hugetlb_cow() should be called with page lock of the original hugepage held.
+ * Called with hugetlb_instantiation_mutex held and pte_page locked so we
+ * cannot race with other handlers or page migration.
+ * Keep the pte_same checks anyway to make transition from the mutex easier.
+ */
+static vm_fault_t hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
+		       unsigned long address, pte_t *ptep,
+		       struct page *pagecache_page, spinlock_t *ptl)
+{
+	pte_t pte;
+	struct hstate *h = hstate_vma(vma);
+	struct page *old_page, *new_page;
+	int outside_reserve = 0;
+	vm_fault_t ret = 0;
+	unsigned long mmun_start;	/* For mmu_notifiers */
+	unsigned long mmun_end;		/* For mmu_notifiers */
+	unsigned long haddr = address & huge_page_mask(h);
+
+	pte = huge_ptep_get(ptep);
+	old_page = pte_page(pte);
+
+retry_avoidcopy:
+	/* If no-one else is actually using this page, avoid the copy
+	 * and just make the page writable */
+	if (page_mapcount(old_page) == 1 && PageAnon(old_page)) {
+		page_move_anon_rmap(old_page, vma);
+		set_huge_ptep_writable(vma, haddr, ptep);
+		return 0;
+	}
+
+	/*
+	 * If the process that created a MAP_PRIVATE mapping is about to
+	 * perform a COW due to a shared page count, attempt to satisfy
+	 * the allocation without using the existing reserves. The pagecache
+	 * page is used to determine if the reserve at this address was
+	 * consumed or not. If reserves were used, a partial faulted mapping
+	 * at the time of fork() could consume its reserves on COW instead
+	 * of the full address range.
+	 */
+	if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) &&
+			old_page != pagecache_page)
+		outside_reserve = 1;
+
+	get_page(old_page);
+
+	/*
+	 * Drop page table lock as buddy allocator may be called. It will
+	 * be acquired again before returning to the caller, as expected.
+	 */
+	spin_unlock(ptl);
+	new_page = alloc_huge_page(vma, haddr, outside_reserve);
+
+	if (IS_ERR(new_page)) {
+		/*
+		 * If a process owning a MAP_PRIVATE mapping fails to COW,
+		 * it is due to references held by a child and an insufficient
+		 * huge page pool. To guarantee the original mappers
+		 * reliability, unmap the page from child processes. The child
+		 * may get SIGKILLed if it later faults.
+		 */
+		if (outside_reserve) {
+			put_page(old_page);
+			BUG_ON(huge_pte_none(pte));
+			unmap_ref_private(mm, vma, old_page, haddr);
+			BUG_ON(huge_pte_none(pte));
+			spin_lock(ptl);
+			ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
+			if (likely(ptep &&
+				   pte_same(huge_ptep_get(ptep), pte)))
+				goto retry_avoidcopy;
+			/*
+			 * race occurs while re-acquiring page table
+			 * lock, and our job is done.
+			 */
+			return 0;
+		}
+
+		ret = vmf_error(PTR_ERR(new_page));
+		goto out_release_old;
+	}
+
+	/*
+	 * When the original hugepage is shared one, it does not have
+	 * anon_vma prepared.
+	 */
+	if (unlikely(anon_vma_prepare(vma))) {
+		ret = VM_FAULT_OOM;
+		goto out_release_all;
+	}
+
+	copy_user_huge_page(new_page, old_page, address, vma,
+			    pages_per_huge_page(h));
+	__SetPageUptodate(new_page);
+	set_page_huge_active(new_page);
+
+	mmun_start = haddr;
+	mmun_end = mmun_start + huge_page_size(h);
+	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
+
+	/*
+	 * Retake the page table lock to check for racing updates
+	 * before the page tables are altered
+	 */
+	spin_lock(ptl);
+	ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
+	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
+		ClearPagePrivate(new_page);
+
+		/* Break COW */
+		huge_ptep_clear_flush(vma, haddr, ptep);
+		mmu_notifier_invalidate_range(mm, mmun_start, mmun_end);
+		set_huge_pte_at(mm, haddr, ptep,
+				make_huge_pte(vma, new_page, 1));
+		page_remove_rmap(old_page, true);
+		hugepage_add_new_anon_rmap(new_page, vma, haddr);
+		/* Make the old page be freed below */
+		new_page = old_page;
+	}
+	spin_unlock(ptl);
+	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
+out_release_all:
+	restore_reserve_on_error(h, vma, haddr, new_page);
+	put_page(new_page);
+out_release_old:
+	put_page(old_page);
+
+	spin_lock(ptl); /* Caller expects lock to be held */
+	return ret;
+}
+
+/* Return the pagecache page at a given address within a VMA */
+static struct page *hugetlbfs_pagecache_page(struct hstate *h,
+			struct vm_area_struct *vma, unsigned long address)
+{
+	struct address_space *mapping;
+	pgoff_t idx;
+
+	mapping = vma->vm_file->f_mapping;
+	idx = vma_hugecache_offset(h, vma, address);
+
+	return find_lock_page(mapping, idx);
+}
+
+/*
+ * Return whether there is a pagecache page to back given address within VMA.
+ * Caller follow_hugetlb_page() holds page_table_lock so we cannot lock_page.
+ */
+static bool hugetlbfs_pagecache_present(struct hstate *h,
+			struct vm_area_struct *vma, unsigned long address)
+{
+	struct address_space *mapping;
+	pgoff_t idx;
+	struct page *page;
+
+	mapping = vma->vm_file->f_mapping;
+	idx = vma_hugecache_offset(h, vma, address);
+
+	page = find_get_page(mapping, idx);
+	if (page)
+		put_page(page);
+	return page != NULL;
+}
+
+int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
+			   pgoff_t idx)
+{
+	struct inode *inode = mapping->host;
+	struct hstate *h = hstate_inode(inode);
+	int err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+
+	if (err)
+		return err;
+	ClearPagePrivate(page);
+
+	/*
+	 * set page dirty so that it will not be removed from cache/file
+	 * by non-hugetlbfs specific code paths.
+	 */
+	set_page_dirty(page);
+
+	spin_lock(&inode->i_lock);
+	inode->i_blocks += blocks_per_huge_page(h);
+	spin_unlock(&inode->i_lock);
+	return 0;
+}
+
+static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
+			struct vm_area_struct *vma,
+			struct address_space *mapping, pgoff_t idx,
+			unsigned long address, pte_t *ptep, unsigned int flags)
+{
+	struct hstate *h = hstate_vma(vma);
+	vm_fault_t ret = VM_FAULT_SIGBUS;
+	int anon_rmap = 0;
+	unsigned long size;
+	struct page *page;
+	pte_t new_pte;
+	spinlock_t *ptl;
+	unsigned long haddr = address & huge_page_mask(h);
+
+	/*
+	 * Currently, we are forced to kill the process in the event the
+	 * original mapper has unmapped pages from the child due to a failed
+	 * COW. Warn that such a situation has occurred as it may not be obvious
+	 */
+	if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) {
+		pr_warn_ratelimited("PID %d killed due to inadequate hugepage pool\n",
+			   current->pid);
+		return ret;
+	}
+
+	/*
+	 * Use page lock to guard against racing truncation
+	 * before we get page_table_lock.
+	 */
+retry:
+	page = find_lock_page(mapping, idx);
+	if (!page) {
+		size = i_size_read(mapping->host) >> huge_page_shift(h);
+		if (idx >= size)
+			goto out;
+
+		/*
+		 * Check for page in userfault range
+		 */
+		if (userfaultfd_missing(vma)) {
+			u32 hash;
+			struct vm_fault vmf = {
+				.vma = vma,
+				.address = haddr,
+				.flags = flags,
+				/*
+				 * Hard to debug if it ends up being
+				 * used by a callee that assumes
+				 * something about the other
+				 * uninitialized fields... same as in
+				 * memory.c
+				 */
+			};
+
+			/*
+			 * hugetlb_fault_mutex must be dropped before
+			 * handling userfault.  Reacquire after handling
+			 * fault to make calling code simpler.
+			 */
+			hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping,
+							idx, haddr);
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+			ret = handle_userfault(&vmf, VM_UFFD_MISSING);
+			mutex_lock(&hugetlb_fault_mutex_table[hash]);
+			goto out;
+		}
+
+		page = alloc_huge_page(vma, haddr, 0);
+		if (IS_ERR(page)) {
+			ret = vmf_error(PTR_ERR(page));
+			goto out;
+		}
+		clear_huge_page(page, address, pages_per_huge_page(h));
+		__SetPageUptodate(page);
+		set_page_huge_active(page);
+
+		if (vma->vm_flags & VM_MAYSHARE) {
+			int err = huge_add_to_page_cache(page, mapping, idx);
+			if (err) {
+				put_page(page);
+				if (err == -EEXIST)
+					goto retry;
+				goto out;
+			}
+		} else {
+			lock_page(page);
+			if (unlikely(anon_vma_prepare(vma))) {
+				ret = VM_FAULT_OOM;
+				goto backout_unlocked;
+			}
+			anon_rmap = 1;
+		}
+	} else {
+		/*
+		 * If memory error occurs between mmap() and fault, some process
+		 * don't have hwpoisoned swap entry for errored virtual address.
+		 * So we need to block hugepage fault by PG_hwpoison bit check.
+		 */
+		if (unlikely(PageHWPoison(page))) {
+			ret = VM_FAULT_HWPOISON |
+				VM_FAULT_SET_HINDEX(hstate_index(h));
+			goto backout_unlocked;
+		}
+	}
+
+	/*
+	 * If we are going to COW a private mapping later, we examine the
+	 * pending reservations for this page now. This will ensure that
+	 * any allocations necessary to record that reservation occur outside
+	 * the spinlock.
+	 */
+	if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
+		if (vma_needs_reservation(h, vma, haddr) < 0) {
+			ret = VM_FAULT_OOM;
+			goto backout_unlocked;
+		}
+		/* Just decrements count, does not deallocate */
+		vma_end_reservation(h, vma, haddr);
+	}
+
+	ptl = huge_pte_lock(h, mm, ptep);
+	size = i_size_read(mapping->host) >> huge_page_shift(h);
+	if (idx >= size)
+		goto backout;
+
+	ret = 0;
+	if (!huge_pte_none(huge_ptep_get(ptep)))
+		goto backout;
+
+	if (anon_rmap) {
+		ClearPagePrivate(page);
+		hugepage_add_new_anon_rmap(page, vma, haddr);
+	} else
+		page_dup_rmap(page, true);
+	new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
+				&& (vma->vm_flags & VM_SHARED)));
+	set_huge_pte_at(mm, haddr, ptep, new_pte);
+
+	hugetlb_count_add(pages_per_huge_page(h), mm);
+	if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
+		/* Optimization, do the COW without a second fault */
+		ret = hugetlb_cow(mm, vma, address, ptep, page, ptl);
+	}
+
+	spin_unlock(ptl);
+	unlock_page(page);
+out:
+	return ret;
+
+backout:
+	spin_unlock(ptl);
+backout_unlocked:
+	unlock_page(page);
+	restore_reserve_on_error(h, vma, haddr, page);
+	put_page(page);
+	goto out;
+}
+
+#ifdef CONFIG_SMP
+u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
+			    struct vm_area_struct *vma,
+			    struct address_space *mapping,
+			    pgoff_t idx, unsigned long address)
+{
+	unsigned long key[2];
+	u32 hash;
+
+	if (vma->vm_flags & VM_SHARED) {
+		key[0] = (unsigned long) mapping;
+		key[1] = idx;
+	} else {
+		key[0] = (unsigned long) mm;
+		key[1] = address >> huge_page_shift(h);
+	}
+
+	hash = jhash2((u32 *)&key, sizeof(key)/sizeof(u32), 0);
+
+	return hash & (num_fault_mutexes - 1);
+}
+#else
+/*
+ * For uniprocesor systems we always use a single mutex, so just
+ * return 0 and avoid the hashing overhead.
+ */
+u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
+			    struct vm_area_struct *vma,
+			    struct address_space *mapping,
+			    pgoff_t idx, unsigned long address)
+{
+	return 0;
+}
+#endif
+
+vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+			unsigned long address, unsigned int flags)
+{
+	pte_t *ptep, entry;
+	spinlock_t *ptl;
+	vm_fault_t ret;
+	u32 hash;
+	pgoff_t idx;
+	struct page *page = NULL;
+	struct page *pagecache_page = NULL;
+	struct hstate *h = hstate_vma(vma);
+	struct address_space *mapping;
+	int need_wait_lock = 0;
+	unsigned long haddr = address & huge_page_mask(h);
+
+	ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
+	if (ptep) {
+		entry = huge_ptep_get(ptep);
+		if (unlikely(is_hugetlb_entry_migration(entry))) {
+			migration_entry_wait_huge(vma, mm, ptep);
+			return 0;
+		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
+			return VM_FAULT_HWPOISON_LARGE |
+				VM_FAULT_SET_HINDEX(hstate_index(h));
+	} else {
+		ptep = huge_pte_alloc(mm, haddr, huge_page_size(h));
+		if (!ptep)
+			return VM_FAULT_OOM;
+	}
+
+	mapping = vma->vm_file->f_mapping;
+	idx = vma_hugecache_offset(h, vma, haddr);
+
+	/*
+	 * Serialize hugepage allocation and instantiation, so that we don't
+	 * get spurious allocation failures if two CPUs race to instantiate
+	 * the same page in the page cache.
+	 */
+	hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping, idx, haddr);
+	mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
+	entry = huge_ptep_get(ptep);
+	if (huge_pte_none(entry)) {
+		ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags);
+		goto out_mutex;
+	}
+
+	ret = 0;
+
+	/*
+	 * entry could be a migration/hwpoison entry at this point, so this
+	 * check prevents the kernel from going below assuming that we have
+	 * a active hugepage in pagecache. This goto expects the 2nd page fault,
+	 * and is_hugetlb_entry_(migration|hwpoisoned) check will properly
+	 * handle it.
+	 */
+	if (!pte_present(entry))
+		goto out_mutex;
+
+	/*
+	 * If we are going to COW the mapping later, we examine the pending
+	 * reservations for this page now. This will ensure that any
+	 * allocations necessary to record that reservation occur outside the
+	 * spinlock. For private mappings, we also lookup the pagecache
+	 * page now as it is used to determine if a reservation has been
+	 * consumed.
+	 */
+	if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
+		if (vma_needs_reservation(h, vma, haddr) < 0) {
+			ret = VM_FAULT_OOM;
+			goto out_mutex;
+		}
+		/* Just decrements count, does not deallocate */
+		vma_end_reservation(h, vma, haddr);
+
+		if (!(vma->vm_flags & VM_MAYSHARE))
+			pagecache_page = hugetlbfs_pagecache_page(h,
+								vma, haddr);
+	}
+
+	ptl = huge_pte_lock(h, mm, ptep);
+
+	/* Check for a racing update before calling hugetlb_cow */
+	if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
+		goto out_ptl;
+
+	/*
+	 * hugetlb_cow() requires page locks of pte_page(entry) and
+	 * pagecache_page, so here we need take the former one
+	 * when page != pagecache_page or !pagecache_page.
+	 */
+	page = pte_page(entry);
+	if (page != pagecache_page)
+		if (!trylock_page(page)) {
+			need_wait_lock = 1;
+			goto out_ptl;
+		}
+
+	get_page(page);
+
+	if (flags & FAULT_FLAG_WRITE) {
+		if (!huge_pte_write(entry)) {
+			ret = hugetlb_cow(mm, vma, address, ptep,
+					  pagecache_page, ptl);
+			goto out_put_page;
+		}
+		entry = huge_pte_mkdirty(entry);
+	}
+	entry = pte_mkyoung(entry);
+	if (huge_ptep_set_access_flags(vma, haddr, ptep, entry,
+						flags & FAULT_FLAG_WRITE))
+		update_mmu_cache(vma, haddr, ptep);
+out_put_page:
+	if (page != pagecache_page)
+		unlock_page(page);
+	put_page(page);
+out_ptl:
+	spin_unlock(ptl);
+
+	if (pagecache_page) {
+		unlock_page(pagecache_page);
+		put_page(pagecache_page);
+	}
+out_mutex:
+	mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+	/*
+	 * Generally it's safe to hold refcount during waiting page lock. But
+	 * here we just wait to defer the next page fault to avoid busy loop and
+	 * the page is not used after unlocked before returning from the current
+	 * page fault. So we are safe from accessing freed page, even if we wait
+	 * here without taking refcount.
+	 */
+	if (need_wait_lock)
+		wait_on_page_locked(page);
+	return ret;
+}
+
+/*
+ * Used by userfaultfd UFFDIO_COPY.  Based on mcopy_atomic_pte with
+ * modifications for huge pages.
+ */
+int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
+			    pte_t *dst_pte,
+			    struct vm_area_struct *dst_vma,
+			    unsigned long dst_addr,
+			    unsigned long src_addr,
+			    struct page **pagep)
+{
+	struct address_space *mapping;
+	pgoff_t idx;
+	unsigned long size;
+	int vm_shared = dst_vma->vm_flags & VM_SHARED;
+	struct hstate *h = hstate_vma(dst_vma);
+	pte_t _dst_pte;
+	spinlock_t *ptl;
+	int ret;
+	struct page *page;
+
+	if (!*pagep) {
+		ret = -ENOMEM;
+		page = alloc_huge_page(dst_vma, dst_addr, 0);
+		if (IS_ERR(page))
+			goto out;
+
+		ret = copy_huge_page_from_user(page,
+						(const void __user *) src_addr,
+						pages_per_huge_page(h), false);
+
+		/* fallback to copy_from_user outside mmap_sem */
+		if (unlikely(ret)) {
+			ret = -ENOENT;
+			*pagep = page;
+			/* don't free the page */
+			goto out;
+		}
+	} else {
+		page = *pagep;
+		*pagep = NULL;
+	}
+
+	/*
+	 * The memory barrier inside __SetPageUptodate makes sure that
+	 * preceding stores to the page contents become visible before
+	 * the set_pte_at() write.
+	 */
+	__SetPageUptodate(page);
+	set_page_huge_active(page);
+
+	mapping = dst_vma->vm_file->f_mapping;
+	idx = vma_hugecache_offset(h, dst_vma, dst_addr);
+
+	/*
+	 * If shared, add to page cache
+	 */
+	if (vm_shared) {
+		size = i_size_read(mapping->host) >> huge_page_shift(h);
+		ret = -EFAULT;
+		if (idx >= size)
+			goto out_release_nounlock;
+
+		/*
+		 * Serialization between remove_inode_hugepages() and
+		 * huge_add_to_page_cache() below happens through the
+		 * hugetlb_fault_mutex_table that here must be hold by
+		 * the caller.
+		 */
+		ret = huge_add_to_page_cache(page, mapping, idx);
+		if (ret)
+			goto out_release_nounlock;
+	}
+
+	ptl = huge_pte_lockptr(h, dst_mm, dst_pte);
+	spin_lock(ptl);
+
+	/*
+	 * Recheck the i_size after holding PT lock to make sure not
+	 * to leave any page mapped (as page_mapped()) beyond the end
+	 * of the i_size (remove_inode_hugepages() is strict about
+	 * enforcing that). If we bail out here, we'll also leave a
+	 * page in the radix tree in the vm_shared case beyond the end
+	 * of the i_size, but remove_inode_hugepages() will take care
+	 * of it as soon as we drop the hugetlb_fault_mutex_table.
+	 */
+	size = i_size_read(mapping->host) >> huge_page_shift(h);
+	ret = -EFAULT;
+	if (idx >= size)
+		goto out_release_unlock;
+
+	ret = -EEXIST;
+	if (!huge_pte_none(huge_ptep_get(dst_pte)))
+		goto out_release_unlock;
+
+	if (vm_shared) {
+		page_dup_rmap(page, true);
+	} else {
+		ClearPagePrivate(page);
+		hugepage_add_new_anon_rmap(page, dst_vma, dst_addr);
+	}
+
+	_dst_pte = make_huge_pte(dst_vma, page, dst_vma->vm_flags & VM_WRITE);
+	if (dst_vma->vm_flags & VM_WRITE)
+		_dst_pte = huge_pte_mkdirty(_dst_pte);
+	_dst_pte = pte_mkyoung(_dst_pte);
+
+	set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+
+	(void)huge_ptep_set_access_flags(dst_vma, dst_addr, dst_pte, _dst_pte,
+					dst_vma->vm_flags & VM_WRITE);
+	hugetlb_count_add(pages_per_huge_page(h), dst_mm);
+
+	/* No need to invalidate - it was non-present before */
+	update_mmu_cache(dst_vma, dst_addr, dst_pte);
+
+	spin_unlock(ptl);
+	if (vm_shared)
+		unlock_page(page);
+	ret = 0;
+out:
+	return ret;
+out_release_unlock:
+	spin_unlock(ptl);
+	if (vm_shared)
+		unlock_page(page);
+out_release_nounlock:
+	put_page(page);
+	goto out;
+}
+
+long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
+			 struct page **pages, struct vm_area_struct **vmas,
+			 unsigned long *position, unsigned long *nr_pages,
+			 long i, unsigned int flags, int *nonblocking)
+{
+	unsigned long pfn_offset;
+	unsigned long vaddr = *position;
+	unsigned long remainder = *nr_pages;
+	struct hstate *h = hstate_vma(vma);
+	int err = -EFAULT;
+
+	while (vaddr < vma->vm_end && remainder) {
+		pte_t *pte;
+		spinlock_t *ptl = NULL;
+		int absent;
+		struct page *page;
+
+		/*
+		 * If we have a pending SIGKILL, don't keep faulting pages and
+		 * potentially allocating memory.
+		 */
+		if (unlikely(fatal_signal_pending(current))) {
+			remainder = 0;
+			break;
+		}
+
+		/*
+		 * Some archs (sparc64, sh*) have multiple pte_ts to
+		 * each hugepage.  We have to make sure we get the
+		 * first, for the page indexing below to work.
+		 *
+		 * Note that page table lock is not held when pte is null.
+		 */
+		pte = huge_pte_offset(mm, vaddr & huge_page_mask(h),
+				      huge_page_size(h));
+		if (pte)
+			ptl = huge_pte_lock(h, mm, pte);
+		absent = !pte || huge_pte_none(huge_ptep_get(pte));
+
+		/*
+		 * When coredumping, it suits get_dump_page if we just return
+		 * an error where there's an empty slot with no huge pagecache
+		 * to back it.  This way, we avoid allocating a hugepage, and
+		 * the sparse dumpfile avoids allocating disk blocks, but its
+		 * huge holes still show up with zeroes where they need to be.
+		 */
+		if (absent && (flags & FOLL_DUMP) &&
+		    !hugetlbfs_pagecache_present(h, vma, vaddr)) {
+			if (pte)
+				spin_unlock(ptl);
+			remainder = 0;
+			break;
+		}
+
+		/*
+		 * We need call hugetlb_fault for both hugepages under migration
+		 * (in which case hugetlb_fault waits for the migration,) and
+		 * hwpoisoned hugepages (in which case we need to prevent the
+		 * caller from accessing to them.) In order to do this, we use
+		 * here is_swap_pte instead of is_hugetlb_entry_migration and
+		 * is_hugetlb_entry_hwpoisoned. This is because it simply covers
+		 * both cases, and because we can't follow correct pages
+		 * directly from any kind of swap entries.
+		 */
+		if (absent || is_swap_pte(huge_ptep_get(pte)) ||
+		    ((flags & FOLL_WRITE) &&
+		      !huge_pte_write(huge_ptep_get(pte)))) {
+			vm_fault_t ret;
+			unsigned int fault_flags = 0;
+
+			if (pte)
+				spin_unlock(ptl);
+			if (flags & FOLL_WRITE)
+				fault_flags |= FAULT_FLAG_WRITE;
+			if (nonblocking)
+				fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+			if (flags & FOLL_NOWAIT)
+				fault_flags |= FAULT_FLAG_ALLOW_RETRY |
+					FAULT_FLAG_RETRY_NOWAIT;
+			if (flags & FOLL_TRIED) {
+				VM_WARN_ON_ONCE(fault_flags &
+						FAULT_FLAG_ALLOW_RETRY);
+				fault_flags |= FAULT_FLAG_TRIED;
+			}
+			ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
+			if (ret & VM_FAULT_ERROR) {
+				err = vm_fault_to_errno(ret, flags);
+				remainder = 0;
+				break;
+			}
+			if (ret & VM_FAULT_RETRY) {
+				if (nonblocking)
+					*nonblocking = 0;
+				*nr_pages = 0;
+				/*
+				 * VM_FAULT_RETRY must not return an
+				 * error, it will return zero
+				 * instead.
+				 *
+				 * No need to update "position" as the
+				 * caller will not check it after
+				 * *nr_pages is set to 0.
+				 */
+				return i;
+			}
+			continue;
+		}
+
+		pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT;
+		page = pte_page(huge_ptep_get(pte));
+same_page:
+		if (pages) {
+			pages[i] = mem_map_offset(page, pfn_offset);
+			get_page(pages[i]);
+		}
+
+		if (vmas)
+			vmas[i] = vma;
+
+		vaddr += PAGE_SIZE;
+		++pfn_offset;
+		--remainder;
+		++i;
+		if (vaddr < vma->vm_end && remainder &&
+				pfn_offset < pages_per_huge_page(h)) {
+			/*
+			 * We use pfn_offset to avoid touching the pageframes
+			 * of this compound page.
+			 */
+			goto same_page;
+		}
+		spin_unlock(ptl);
+	}
+	*nr_pages = remainder;
+	/*
+	 * setting position is actually required only if remainder is
+	 * not zero but it's faster not to add a "if (remainder)"
+	 * branch.
+	 */
+	*position = vaddr;
+
+	return i ? i : err;
+}
+
+#ifndef __HAVE_ARCH_FLUSH_HUGETLB_TLB_RANGE
+/*
+ * ARCHes with special requirements for evicting HUGETLB backing TLB entries can
+ * implement this.
+ */
+#define flush_hugetlb_tlb_range(vma, addr, end)	flush_tlb_range(vma, addr, end)
+#endif
+
+unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
+		unsigned long address, unsigned long end, pgprot_t newprot)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	unsigned long start = address;
+	pte_t *ptep;
+	pte_t pte;
+	struct hstate *h = hstate_vma(vma);
+	unsigned long pages = 0;
+	unsigned long f_start = start;
+	unsigned long f_end = end;
+	bool shared_pmd = false;
+
+	/*
+	 * In the case of shared PMDs, the area to flush could be beyond
+	 * start/end.  Set f_start/f_end to cover the maximum possible
+	 * range if PMD sharing is possible.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &f_start, &f_end);
+
+	BUG_ON(address >= end);
+	flush_cache_range(vma, f_start, f_end);
+
+	mmu_notifier_invalidate_range_start(mm, f_start, f_end);
+	i_mmap_lock_write(vma->vm_file->f_mapping);
+	for (; address < end; address += huge_page_size(h)) {
+		spinlock_t *ptl;
+		ptep = huge_pte_offset(mm, address, huge_page_size(h));
+		if (!ptep)
+			continue;
+		ptl = huge_pte_lock(h, mm, ptep);
+		if (huge_pmd_unshare(mm, &address, ptep)) {
+			pages++;
+			spin_unlock(ptl);
+			shared_pmd = true;
+			continue;
+		}
+		pte = huge_ptep_get(ptep);
+		if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
+			spin_unlock(ptl);
+			continue;
+		}
+		if (unlikely(is_hugetlb_entry_migration(pte))) {
+			swp_entry_t entry = pte_to_swp_entry(pte);
+
+			if (is_write_migration_entry(entry)) {
+				pte_t newpte;
+
+				make_migration_entry_read(&entry);
+				newpte = swp_entry_to_pte(entry);
+				set_huge_swap_pte_at(mm, address, ptep,
+						     newpte, huge_page_size(h));
+				pages++;
+			}
+			spin_unlock(ptl);
+			continue;
+		}
+		if (!huge_pte_none(pte)) {
+			pte = huge_ptep_get_and_clear(mm, address, ptep);
+			pte = pte_mkhuge(huge_pte_modify(pte, newprot));
+			pte = arch_make_huge_pte(pte, vma, NULL, 0);
+			set_huge_pte_at(mm, address, ptep, pte);
+			pages++;
+		}
+		spin_unlock(ptl);
+	}
+	/*
+	 * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
+	 * may have cleared our pud entry and done put_page on the page table:
+	 * once we release i_mmap_rwsem, another task can do the final put_page
+	 * and that page table be reused and filled with junk.  If we actually
+	 * did unshare a page of pmds, flush the range corresponding to the pud.
+	 */
+	if (shared_pmd)
+		flush_hugetlb_tlb_range(vma, f_start, f_end);
+	else
+		flush_hugetlb_tlb_range(vma, start, end);
+	/*
+	 * No need to call mmu_notifier_invalidate_range() we are downgrading
+	 * page table protection not changing it to point to a new page.
+	 *
+	 * See Documentation/vm/mmu_notifier.rst
+	 */
+	i_mmap_unlock_write(vma->vm_file->f_mapping);
+	mmu_notifier_invalidate_range_end(mm, f_start, f_end);
+
+	return pages << h->order;
+}
+
+int hugetlb_reserve_pages(struct inode *inode,
+					long from, long to,
+					struct vm_area_struct *vma,
+					vm_flags_t vm_flags)
+{
+	long ret, chg;
+	struct hstate *h = hstate_inode(inode);
+	struct hugepage_subpool *spool = subpool_inode(inode);
+	struct resv_map *resv_map;
+	long gbl_reserve;
+
+	/* This should never happen */
+	if (from > to) {
+		VM_WARN(1, "%s called with a negative range\n", __func__);
+		return -EINVAL;
+	}
+
+	/*
+	 * Only apply hugepage reservation if asked. At fault time, an
+	 * attempt will be made for VM_NORESERVE to allocate a page
+	 * without using reserves
+	 */
+	if (vm_flags & VM_NORESERVE)
+		return 0;
+
+	/*
+	 * Shared mappings base their reservation on the number of pages that
+	 * are already allocated on behalf of the file. Private mappings need
+	 * to reserve the full area even if read-only as mprotect() may be
+	 * called to make the mapping read-write. Assume !vma is a shm mapping
+	 */
+	if (!vma || vma->vm_flags & VM_MAYSHARE) {
+		resv_map = inode_resv_map(inode);
+
+		chg = region_chg(resv_map, from, to);
+
+	} else {
+		resv_map = resv_map_alloc();
+		if (!resv_map)
+			return -ENOMEM;
+
+		chg = to - from;
+
+		set_vma_resv_map(vma, resv_map);
+		set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
+	}
+
+	if (chg < 0) {
+		ret = chg;
+		goto out_err;
+	}
+
+	/*
+	 * There must be enough pages in the subpool for the mapping. If
+	 * the subpool has a minimum size, there may be some global
+	 * reservations already in place (gbl_reserve).
+	 */
+	gbl_reserve = hugepage_subpool_get_pages(spool, chg);
+	if (gbl_reserve < 0) {
+		ret = -ENOSPC;
+		goto out_err;
+	}
+
+	/*
+	 * Check enough hugepages are available for the reservation.
+	 * Hand the pages back to the subpool if there are not
+	 */
+	ret = hugetlb_acct_memory(h, gbl_reserve);
+	if (ret < 0) {
+		/* put back original number of pages, chg */
+		(void)hugepage_subpool_put_pages(spool, chg);
+		goto out_err;
+	}
+
+	/*
+	 * Account for the reservations made. Shared mappings record regions
+	 * that have reservations as they are shared by multiple VMAs.
+	 * When the last VMA disappears, the region map says how much
+	 * the reservation was and the page cache tells how much of
+	 * the reservation was consumed. Private mappings are per-VMA and
+	 * only the consumed reservations are tracked. When the VMA
+	 * disappears, the original reservation is the VMA size and the
+	 * consumed reservations are stored in the map. Hence, nothing
+	 * else has to be done for private mappings here
+	 */
+	if (!vma || vma->vm_flags & VM_MAYSHARE) {
+		long add = region_add(resv_map, from, to);
+
+		if (unlikely(chg > add)) {
+			/*
+			 * pages in this range were added to the reserve
+			 * map between region_chg and region_add.  This
+			 * indicates a race with alloc_huge_page.  Adjust
+			 * the subpool and reserve counts modified above
+			 * based on the difference.
+			 */
+			long rsv_adjust;
+
+			rsv_adjust = hugepage_subpool_put_pages(spool,
+								chg - add);
+			hugetlb_acct_memory(h, -rsv_adjust);
+		}
+	}
+	return 0;
+out_err:
+	if (!vma || vma->vm_flags & VM_MAYSHARE)
+		/* Don't call region_abort if region_chg failed */
+		if (chg >= 0)
+			region_abort(resv_map, from, to);
+	if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
+		kref_put(&resv_map->refs, resv_map_release);
+	return ret;
+}
+
+long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
+								long freed)
+{
+	struct hstate *h = hstate_inode(inode);
+	struct resv_map *resv_map = inode_resv_map(inode);
+	long chg = 0;
+	struct hugepage_subpool *spool = subpool_inode(inode);
+	long gbl_reserve;
+
+	if (resv_map) {
+		chg = region_del(resv_map, start, end);
+		/*
+		 * region_del() can fail in the rare case where a region
+		 * must be split and another region descriptor can not be
+		 * allocated.  If end == LONG_MAX, it will not fail.
+		 */
+		if (chg < 0)
+			return chg;
+	}
+
+	spin_lock(&inode->i_lock);
+	inode->i_blocks -= (blocks_per_huge_page(h) * freed);
+	spin_unlock(&inode->i_lock);
+
+	/*
+	 * If the subpool has a minimum size, the number of global
+	 * reservations to be released may be adjusted.
+	 */
+	gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
+	hugetlb_acct_memory(h, -gbl_reserve);
+
+	return 0;
+}
+
+#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
+static unsigned long page_table_shareable(struct vm_area_struct *svma,
+				struct vm_area_struct *vma,
+				unsigned long addr, pgoff_t idx)
+{
+	unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
+				svma->vm_start;
+	unsigned long sbase = saddr & PUD_MASK;
+	unsigned long s_end = sbase + PUD_SIZE;
+
+	/* Allow segments to share if only one is marked locked */
+	unsigned long vm_flags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
+	unsigned long svm_flags = svma->vm_flags & VM_LOCKED_CLEAR_MASK;
+
+	/*
+	 * match the virtual addresses, permission and the alignment of the
+	 * page table page.
+	 */
+	if (pmd_index(addr) != pmd_index(saddr) ||
+	    vm_flags != svm_flags ||
+	    sbase < svma->vm_start || svma->vm_end < s_end)
+		return 0;
+
+	return saddr;
+}
+
+static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr)
+{
+	unsigned long base = addr & PUD_MASK;
+	unsigned long end = base + PUD_SIZE;
+
+	/*
+	 * check on proper vm_flags and page table alignment
+	 */
+	if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end))
+		return true;
+	return false;
+}
+
+/*
+ * Determine if start,end range within vma could be mapped by shared pmd.
+ * If yes, adjust start and end to cover range associated with possible
+ * shared pmd mappings.
+ */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
+				unsigned long *start, unsigned long *end)
+{
+	unsigned long check_addr = *start;
+
+	if (!(vma->vm_flags & VM_MAYSHARE))
+		return;
+
+	for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
+		unsigned long a_start = check_addr & PUD_MASK;
+		unsigned long a_end = a_start + PUD_SIZE;
+
+		/*
+		 * If sharing is possible, adjust start/end if necessary.
+		 */
+		if (range_in_vma(vma, a_start, a_end)) {
+			if (a_start < *start)
+				*start = a_start;
+			if (a_end > *end)
+				*end = a_end;
+		}
+	}
+}
+
+/*
+ * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
+ * and returns the corresponding pte. While this is not necessary for the
+ * !shared pmd case because we can allocate the pmd later as well, it makes the
+ * code much cleaner. pmd allocation is essential for the shared case because
+ * pud has to be populated inside the same i_mmap_rwsem section - otherwise
+ * racing tasks could either miss the sharing (see huge_pte_offset) or select a
+ * bad pmd for sharing.
+ */
+pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
+{
+	struct vm_area_struct *vma = find_vma(mm, addr);
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
+			vma->vm_pgoff;
+	struct vm_area_struct *svma;
+	unsigned long saddr;
+	pte_t *spte = NULL;
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	if (!vma_shareable(vma, addr))
+		return (pte_t *)pmd_alloc(mm, pud, addr);
+
+	i_mmap_lock_write(mapping);
+	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
+		if (svma == vma)
+			continue;
+
+		saddr = page_table_shareable(svma, vma, addr, idx);
+		if (saddr) {
+			spte = huge_pte_offset(svma->vm_mm, saddr,
+					       vma_mmu_pagesize(svma));
+			if (spte) {
+				get_page(virt_to_page(spte));
+				break;
+			}
+		}
+	}
+
+	if (!spte)
+		goto out;
+
+	ptl = huge_pte_lock(hstate_vma(vma), mm, spte);
+	if (pud_none(*pud)) {
+		pud_populate(mm, pud,
+				(pmd_t *)((unsigned long)spte & PAGE_MASK));
+		mm_inc_nr_pmds(mm);
+	} else {
+		put_page(virt_to_page(spte));
+	}
+	spin_unlock(ptl);
+out:
+	pte = (pte_t *)pmd_alloc(mm, pud, addr);
+	i_mmap_unlock_write(mapping);
+	return pte;
+}
+
+/*
+ * unmap huge page backed by shared pte.
+ *
+ * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
+ * indicated by page_count > 1, unmap is achieved by clearing pud and
+ * decrementing the ref count. If count == 1, the pte page is not shared.
+ *
+ * called with page table lock held.
+ *
+ * returns: 1 successfully unmapped a shared pte page
+ *	    0 the underlying pte page is not shared, or it is the last user
+ */
+int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
+{
+	pgd_t *pgd = pgd_offset(mm, *addr);
+	p4d_t *p4d = p4d_offset(pgd, *addr);
+	pud_t *pud = pud_offset(p4d, *addr);
+
+	BUG_ON(page_count(virt_to_page(ptep)) == 0);
+	if (page_count(virt_to_page(ptep)) == 1)
+		return 0;
+
+	pud_clear(pud);
+	put_page(virt_to_page(ptep));
+	mm_dec_nr_pmds(mm);
+	*addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
+	return 1;
+}
+#define want_pmd_share()	(1)
+#else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
+pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
+{
+	return NULL;
+}
+
+int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
+{
+	return 0;
+}
+
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
+				unsigned long *start, unsigned long *end)
+{
+}
+#define want_pmd_share()	(0)
+#endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
+
+#ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
+pte_t *huge_pte_alloc(struct mm_struct *mm,
+			unsigned long addr, unsigned long sz)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pte_t *pte = NULL;
+
+	pgd = pgd_offset(mm, addr);
+	p4d = p4d_alloc(mm, pgd, addr);
+	if (!p4d)
+		return NULL;
+	pud = pud_alloc(mm, p4d, addr);
+	if (pud) {
+		if (sz == PUD_SIZE) {
+			pte = (pte_t *)pud;
+		} else {
+			BUG_ON(sz != PMD_SIZE);
+			if (want_pmd_share() && pud_none(*pud))
+				pte = huge_pmd_share(mm, addr, pud);
+			else
+				pte = (pte_t *)pmd_alloc(mm, pud, addr);
+		}
+	}
+	BUG_ON(pte && pte_present(*pte) && !pte_huge(*pte));
+
+	return pte;
+}
+
+/*
+ * huge_pte_offset() - Walk the page table to resolve the hugepage
+ * entry at address @addr
+ *
+ * Return: Pointer to page table or swap entry (PUD or PMD) for
+ * address @addr, or NULL if a p*d_none() entry is encountered and the
+ * size @sz doesn't match the hugepage size at this level of the page
+ * table.
+ */
+pte_t *huge_pte_offset(struct mm_struct *mm,
+		       unsigned long addr, unsigned long sz)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+
+	pgd = pgd_offset(mm, addr);
+	if (!pgd_present(*pgd))
+		return NULL;
+	p4d = p4d_offset(pgd, addr);
+	if (!p4d_present(*p4d))
+		return NULL;
+
+	pud = pud_offset(p4d, addr);
+	if (sz != PUD_SIZE && pud_none(*pud))
+		return NULL;
+	/* hugepage or swap? */
+	if (pud_huge(*pud) || !pud_present(*pud))
+		return (pte_t *)pud;
+
+	pmd = pmd_offset(pud, addr);
+	if (sz != PMD_SIZE && pmd_none(*pmd))
+		return NULL;
+	/* hugepage or swap? */
+	if (pmd_huge(*pmd) || !pmd_present(*pmd))
+		return (pte_t *)pmd;
+
+	return NULL;
+}
+
+#endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
+
+/*
+ * These functions are overwritable if your architecture needs its own
+ * behavior.
+ */
+struct page * __weak
+follow_huge_addr(struct mm_struct *mm, unsigned long address,
+			      int write)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+struct page * __weak
+follow_huge_pd(struct vm_area_struct *vma,
+	       unsigned long address, hugepd_t hpd, int flags, int pdshift)
+{
+	WARN(1, "hugepd follow called with no support for hugepage directory format\n");
+	return NULL;
+}
+
+struct page * __weak
+follow_huge_pmd(struct mm_struct *mm, unsigned long address,
+		pmd_t *pmd, int flags)
+{
+	struct page *page = NULL;
+	spinlock_t *ptl;
+	pte_t pte;
+retry:
+	ptl = pmd_lockptr(mm, pmd);
+	spin_lock(ptl);
+	/*
+	 * make sure that the address range covered by this pmd is not
+	 * unmapped from other threads.
+	 */
+	if (!pmd_huge(*pmd))
+		goto out;
+	pte = huge_ptep_get((pte_t *)pmd);
+	if (pte_present(pte)) {
+		page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
+		if (flags & FOLL_GET)
+			get_page(page);
+	} else {
+		if (is_hugetlb_entry_migration(pte)) {
+			spin_unlock(ptl);
+			__migration_entry_wait(mm, (pte_t *)pmd, ptl);
+			goto retry;
+		}
+		/*
+		 * hwpoisoned entry is treated as no_page_table in
+		 * follow_page_mask().
+		 */
+	}
+out:
+	spin_unlock(ptl);
+	return page;
+}
+
+struct page * __weak
+follow_huge_pud(struct mm_struct *mm, unsigned long address,
+		pud_t *pud, int flags)
+{
+	if (flags & FOLL_GET)
+		return NULL;
+
+	return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+}
+
+struct page * __weak
+follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int flags)
+{
+	if (flags & FOLL_GET)
+		return NULL;
+
+	return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
+}
+
+bool isolate_huge_page(struct page *page, struct list_head *list)
+{
+	bool ret = true;
+
+	VM_BUG_ON_PAGE(!PageHead(page), page);
+	spin_lock(&hugetlb_lock);
+	if (!page_huge_active(page) || !get_page_unless_zero(page)) {
+		ret = false;
+		goto unlock;
+	}
+	clear_page_huge_active(page);
+	list_move_tail(&page->lru, list);
+unlock:
+	spin_unlock(&hugetlb_lock);
+	return ret;
+}
+
+void putback_active_hugepage(struct page *page)
+{
+	VM_BUG_ON_PAGE(!PageHead(page), page);
+	spin_lock(&hugetlb_lock);
+	set_page_huge_active(page);
+	list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist);
+	spin_unlock(&hugetlb_lock);
+	put_page(page);
+}
+
+void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason)
+{
+	struct hstate *h = page_hstate(oldpage);
+
+	hugetlb_cgroup_migrate(oldpage, newpage);
+	set_page_owner_migrate_reason(newpage, reason);
+
+	/*
+	 * transfer temporary state of the new huge page. This is
+	 * reverse to other transitions because the newpage is going to
+	 * be final while the old one will be freed so it takes over
+	 * the temporary status.
+	 *
+	 * Also note that we have to transfer the per-node surplus state
+	 * here as well otherwise the global surplus count will not match
+	 * the per-node's.
+	 */
+	if (PageHugeTemporary(newpage)) {
+		int old_nid = page_to_nid(oldpage);
+		int new_nid = page_to_nid(newpage);
+
+		SetPageHugeTemporary(oldpage);
+		ClearPageHugeTemporary(newpage);
+
+		spin_lock(&hugetlb_lock);
+		if (h->surplus_huge_pages_node[old_nid]) {
+			h->surplus_huge_pages_node[old_nid]--;
+			h->surplus_huge_pages_node[new_nid]++;
+		}
+		spin_unlock(&hugetlb_lock);
+	}
+}