/*
   * Generic hugetlb support.
   * (C) William Irwin, April 2004
   */

  #include <linux/list.h>
  #include <linux/init.h>
  #include <linux/module.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/cpuset.h>

  #include <linux/mutex.h>

  #include <linux/bootmem.h>

  #include <linux/sysfs.h>

  #include <linux/slab.h>

  #include <linux/rmap.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  #include <asm/page.h>
  #include <asm/pgtable.h>

  #include <asm/io.h>

  
  #include <linux/hugetlb.h>

  #include <linux/node.h>

  #include "internal.h"

  
  const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;

  static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
  unsigned long hugepages_treat_as_movable;

  static int max_hstate;
  unsigned int default_hstate_idx;
  struct hstate hstates[HUGE_MAX_HSTATE];

  __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;

  
  #define for_each_hstate(h) \
  	for ((h) = hstates; (h) < &hstates[max_hstate]; (h)++)

  /*
   * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
   */
  static DEFINE_SPINLOCK(hugetlb_lock);

  /*

   * Region tracking -- allows tracking of reservations and instantiated pages
   *                    across the pages in a mapping.

   *
   * The region data structures are protected by a combination of the mmap_sem
   * and the hugetlb_instantion_mutex.  To access or modify a region the caller
   * must either hold the mmap_sem for write, or the mmap_sem for read and
   * the hugetlb_instantiation mutex:
   *
   * 	down_write(&mm->mmap_sem);
   * or
   * 	down_read(&mm->mmap_sem);
   * 	mutex_lock(&hugetlb_instantiation_mutex);

   */
  struct file_region {
  	struct list_head link;
  	long from;
  	long to;
  };
  
  static long region_add(struct list_head *head, long f, long t)
  {
  	struct file_region *rg, *nrg, *trg;
  
  	/* Locate the region we are either in or before. */
  	list_for_each_entry(rg, head, link)
  		if (f <= rg->to)
  			break;
  
  	/* 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) {
  			list_del(&rg->link);
  			kfree(rg);
  		}
  	}
  	nrg->from = f;
  	nrg->to = t;
  	return 0;
  }
  
  static long region_chg(struct list_head *head, long f, long t)
  {
  	struct file_region *rg, *nrg;
  	long chg = 0;
  
  	/* 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) {
  		nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
  		if (!nrg)
  			return -ENOMEM;
  		nrg->from = f;
  		nrg->to   = f;
  		INIT_LIST_HEAD(&nrg->link);
  		list_add(&nrg->link, rg->link.prev);
  
  		return t - f;
  	}
  
  	/* 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)
  			return chg;

  		/* 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;
  	}
  	return chg;
  }
  
  static long region_truncate(struct list_head *head, long end)
  {
  	struct file_region *rg, *trg;
  	long chg = 0;
  
  	/* Locate the region we are either in or before. */
  	list_for_each_entry(rg, head, link)
  		if (end <= rg->to)
  			break;
  	if (&rg->link == head)
  		return 0;
  
  	/* If we are in the middle of a region then adjust it. */
  	if (end > rg->from) {
  		chg = rg->to - end;
  		rg->to = end;
  		rg = list_entry(rg->link.next, typeof(*rg), link);
  	}
  
  	/* Drop any remaining regions. */
  	list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
  		if (&rg->link == head)
  			break;
  		chg += rg->to - rg->from;
  		list_del(&rg->link);
  		kfree(rg);
  	}
  	return chg;
  }

  static long region_count(struct list_head *head, long f, long t)
  {
  	struct file_region *rg;
  	long chg = 0;
  
  	/* Locate each segment we overlap with, and count that overlap. */
  	list_for_each_entry(rg, head, link) {
  		int seg_from;
  		int 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;
  	}
  
  	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);
  }

  /*

   * 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)
  {
  	struct hstate *hstate;
  
  	if (!is_vm_hugetlb_page(vma))
  		return PAGE_SIZE;
  
  	hstate = hstate_vma(vma);
  
  	return 1UL << (hstate->order + PAGE_SHIFT);
  }

  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 version of this
   * function is required.
   */
  #ifndef vma_mmu_pagesize
  unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
  {
  	return vma_kernel_pagesize(vma);
  }
  #endif
  
  /*

   * 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 {
  	struct kref refs;
  	struct list_head regions;
  };

  static struct resv_map *resv_map_alloc(void)

  {
  	struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
  	if (!resv_map)
  		return NULL;
  
  	kref_init(&resv_map->refs);
  	INIT_LIST_HEAD(&resv_map->regions);
  
  	return resv_map;
  }

  static void resv_map_release(struct kref *ref)

  {
  	struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
  
  	/* Clear out any active regions before we release the map. */
  	region_truncate(&resv_map->regions, 0);
  	kfree(resv_map);
  }
  
  static struct resv_map *vma_resv_map(struct vm_area_struct *vma)

  {
  	VM_BUG_ON(!is_vm_hugetlb_page(vma));

  	if (!(vma->vm_flags & VM_MAYSHARE))

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

  	return NULL;

  }

  static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)

  {
  	VM_BUG_ON(!is_vm_hugetlb_page(vma));

  	VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);

  	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(!is_vm_hugetlb_page(vma));

  	VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);

  
  	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(!is_vm_hugetlb_page(vma));

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

  }
  
  /* Decrement the reserved pages in the hugepage pool by one */

  static void decrement_hugepage_resv_vma(struct hstate *h,
  			struct vm_area_struct *vma)

  {

  	if (vma->vm_flags & VM_NORESERVE)
  		return;

  	if (vma->vm_flags & VM_MAYSHARE) {

  		/* Shared mappings always use reserves */

  		h->resv_huge_pages--;

  	} else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {

  		/*
  		 * Only the process that called mmap() has reserves for
  		 * private mappings.
  		 */

  		h->resv_huge_pages--;

  	}
  }

  /* Reset counters to 0 and clear all HPAGE_RESV_* flags */

  void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
  {
  	VM_BUG_ON(!is_vm_hugetlb_page(vma));

  	if (!(vma->vm_flags & VM_MAYSHARE))

  		vma->vm_private_data = (void *)0;
  }
  
  /* Returns true if the VMA has associated reserve pages */

  static int vma_has_reserves(struct vm_area_struct *vma)

  {

  	if (vma->vm_flags & VM_MAYSHARE)

  		return 1;
  	if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
  		return 1;
  	return 0;

  }

  static void copy_gigantic_page(struct page *dst, struct page *src)
  {
  	int i;
  	struct hstate *h = page_hstate(src);
  	struct page *dst_base = dst;
  	struct page *src_base = src;
  
  	for (i = 0; i < pages_per_huge_page(h); ) {
  		cond_resched();
  		copy_highpage(dst, src);
  
  		i++;
  		dst = mem_map_next(dst, dst_base, i);
  		src = mem_map_next(src, src_base, i);
  	}
  }
  
  void copy_huge_page(struct page *dst, struct page *src)
  {
  	int i;
  	struct hstate *h = page_hstate(src);
  
  	if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
  		copy_gigantic_page(dst, src);
  		return;
  	}
  
  	might_sleep();
  	for (i = 0; i < pages_per_huge_page(h); i++) {
  		cond_resched();
  		copy_highpage(dst + i, src + i);
  	}
  }

  static void enqueue_huge_page(struct hstate *h, struct page *page)

  {
  	int nid = page_to_nid(page);

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

  }

  static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
  {
  	struct page *page;
  
  	if (list_empty(&h->hugepage_freelists[nid]))
  		return NULL;
  	page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
  	list_del(&page->lru);

  	set_page_refcounted(page);

  	h->free_huge_pages--;
  	h->free_huge_pages_node[nid]--;
  	return page;
  }

  static struct page *dequeue_huge_page_vma(struct hstate *h,
  				struct vm_area_struct *vma,

  				unsigned long address, int avoid_reserve)

  {

  	struct page *page = NULL;

  	struct mempolicy *mpol;

  	nodemask_t *nodemask;

  	struct zonelist *zonelist;

  	struct zone *zone;
  	struct zoneref *z;

  	get_mems_allowed();
  	zonelist = huge_zonelist(vma, address,
  					htlb_alloc_mask, &mpol, &nodemask);

  	/*
  	 * 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) &&

  			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;

  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
  						MAX_NR_ZONES - 1, nodemask) {

  		if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
  			page = dequeue_huge_page_node(h, zone_to_nid(zone));
  			if (page) {
  				if (!avoid_reserve)
  					decrement_hugepage_resv_vma(h, vma);
  				break;
  			}

  		}

  	}

  err:

  	mpol_cond_put(mpol);

  	put_mems_allowed();

  	return page;
  }

  static void update_and_free_page(struct hstate *h, struct page *page)

  {
  	int i;

  	VM_BUG_ON(h->order >= MAX_ORDER);

  	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_reserved |
  				1 << PG_private | 1<< PG_writeback);
  	}
  	set_compound_page_dtor(page, NULL);
  	set_page_refcounted(page);

  	arch_release_hugepage(page);

  	__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;
  }

  static 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 address_space *mapping;

  	mapping = (struct address_space *) page_private(page);

  	set_page_private(page, 0);

  	page->mapping = NULL;

  	BUG_ON(page_count(page));

  	BUG_ON(page_mapcount(page));

  	INIT_LIST_HEAD(&page->lru);
  
  	spin_lock(&hugetlb_lock);

  	if (h->surplus_huge_pages_node[nid] && huge_page_order(h) < MAX_ORDER) {

  		update_and_free_page(h, page);
  		h->surplus_huge_pages--;
  		h->surplus_huge_pages_node[nid]--;

  	} else {

  		enqueue_huge_page(h, page);

  	}

  	spin_unlock(&hugetlb_lock);

  	if (mapping)

  		hugetlb_put_quota(mapping, 1);

  }

  static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)

  {
  	set_compound_page_dtor(page, free_huge_page);
  	spin_lock(&hugetlb_lock);

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

  	spin_unlock(&hugetlb_lock);
  	put_page(page); /* free it into the hugepage allocator */
  }

  static void prep_compound_gigantic_page(struct page *page, unsigned long 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);
  	__SetPageHead(page);
  	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
  		__SetPageTail(p);
  		p->first_page = page;
  	}
  }
  
  int PageHuge(struct page *page)
  {
  	compound_page_dtor *dtor;
  
  	if (!PageCompound(page))
  		return 0;
  
  	page = compound_head(page);
  	dtor = get_compound_page_dtor(page);
  
  	return dtor == free_huge_page;
  }

  EXPORT_SYMBOL_GPL(PageHuge);

  static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)

  {

  	struct page *page;

  	if (h->order >= MAX_ORDER)
  		return NULL;

  	page = alloc_pages_exact_node(nid,

  		htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
  						__GFP_REPEAT|__GFP_NOWARN,

  		huge_page_order(h));

  	if (page) {

  		if (arch_prepare_hugepage(page)) {

  			__free_pages(page, huge_page_order(h));

  			return NULL;

  		}

  		prep_new_huge_page(h, page, nid);

  	}

  
  	return page;
  }

  /*

   * 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(nid, *nodes_allowed);

  	if (nid == MAX_NUMNODES)

  		nid = first_node(*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;

  }

  static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)

  {
  	struct page *page;
  	int start_nid;
  	int next_nid;
  	int ret = 0;

  	start_nid = hstate_next_node_to_alloc(h, nodes_allowed);

  	next_nid = start_nid;

  
  	do {

  		page = alloc_fresh_huge_page_node(h, next_nid);

  		if (page) {

  			ret = 1;

  			break;
  		}

  		next_nid = hstate_next_node_to_alloc(h, nodes_allowed);

  	} while (next_nid != start_nid);

  	if (ret)
  		count_vm_event(HTLB_BUDDY_PGALLOC);
  	else
  		count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);

  	return ret;

  }

  /*

   * 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;

  }
  
  /*
   * 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 start_nid;
  	int next_nid;
  	int ret = 0;

  	start_nid = hstate_next_node_to_free(h, nodes_allowed);

  	next_nid = start_nid;
  
  	do {

  		/*
  		 * If we're returning unused surplus pages, only examine
  		 * nodes with surplus pages.
  		 */
  		if ((!acct_surplus || h->surplus_huge_pages_node[next_nid]) &&
  		    !list_empty(&h->hugepage_freelists[next_nid])) {

  			struct page *page =
  				list_entry(h->hugepage_freelists[next_nid].next,
  					  struct page, lru);
  			list_del(&page->lru);
  			h->free_huge_pages--;
  			h->free_huge_pages_node[next_nid]--;

  			if (acct_surplus) {
  				h->surplus_huge_pages--;
  				h->surplus_huge_pages_node[next_nid]--;
  			}

  			update_and_free_page(h, page);
  			ret = 1;

  			break;

  		}

  		next_nid = hstate_next_node_to_free(h, nodes_allowed);

  	} while (next_nid != start_nid);

  
  	return ret;
  }

  static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)

  {
  	struct page *page;

  	unsigned int r_nid;

  	if (h->order >= MAX_ORDER)
  		return NULL;

  	/*
  	 * Assume we will successfully allocate the surplus page to
  	 * prevent racing processes from causing the surplus to exceed
  	 * overcommit
  	 *
  	 * This however introduces a different race, where a process B
  	 * tries to grow the static hugepage pool while alloc_pages() is
  	 * called by process A. B will only examine the per-node
  	 * counters in determining if surplus huge pages can be
  	 * converted to normal huge pages in adjust_pool_surplus(). A
  	 * won't be able to increment the per-node counter, until the
  	 * lock is dropped by B, but B doesn't drop hugetlb_lock until
  	 * no more huge pages can be converted from surplus to normal
  	 * state (and doesn't try to convert again). Thus, we have a
  	 * case where a surplus huge page exists, the pool is grown, and
  	 * the surplus huge page still exists after, even though it
  	 * should just have been converted to a normal huge page. This
  	 * does not leak memory, though, as the hugepage will be freed
  	 * once it is out of use. It also does not allow the counters to
  	 * go out of whack in adjust_pool_surplus() as we don't modify
  	 * the node values until we've gotten the hugepage and only the
  	 * per-node value is checked there.
  	 */
  	spin_lock(&hugetlb_lock);

  	if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {

  		spin_unlock(&hugetlb_lock);
  		return NULL;
  	} else {

  		h->nr_huge_pages++;
  		h->surplus_huge_pages++;

  	}
  	spin_unlock(&hugetlb_lock);

  	if (nid == NUMA_NO_NODE)
  		page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
  				   __GFP_REPEAT|__GFP_NOWARN,
  				   huge_page_order(h));
  	else
  		page = alloc_pages_exact_node(nid,
  			htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
  			__GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));

  	if (page && arch_prepare_hugepage(page)) {
  		__free_pages(page, huge_page_order(h));
  		return NULL;
  	}

  	spin_lock(&hugetlb_lock);

  	if (page) {

  		r_nid = page_to_nid(page);

  		set_compound_page_dtor(page, free_huge_page);

  		/*
  		 * We incremented the global counters already
  		 */

  		h->nr_huge_pages_node[r_nid]++;
  		h->surplus_huge_pages_node[r_nid]++;

  		__count_vm_event(HTLB_BUDDY_PGALLOC);

  	} else {

  		h->nr_huge_pages--;
  		h->surplus_huge_pages--;

  		__count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);

  	}

  	spin_unlock(&hugetlb_lock);

  
  	return page;
  }

  /*

   * This allocation function is useful in the context where vma is irrelevant.
   * E.g. soft-offlining uses this function because it only cares physical
   * address of error page.
   */
  struct page *alloc_huge_page_node(struct hstate *h, int nid)
  {
  	struct page *page;
  
  	spin_lock(&hugetlb_lock);
  	page = dequeue_huge_page_node(h, nid);
  	spin_unlock(&hugetlb_lock);
  
  	if (!page)
  		page = alloc_buddy_huge_page(h, nid);
  
  	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;

  	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_buddy_huge_page(h, NUMA_NO_NODE);

  		if (!page)

  			/*
  			 * We were not able to allocate enough pages to
  			 * satisfy the entire reservation so we free what
  			 * we've allocated so far.
  			 */

  			goto free;

  
  		list_add(&page->lru, &surplus_list);
  	}
  	allocated += needed;
  
  	/*
  	 * 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)
  		goto retry;
  
  	/*
  	 * 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;

  
  	spin_unlock(&hugetlb_lock);

  	/* Free the needed pages to the hugetlb pool */

  	list_for_each_entry_safe(page, tmp, &surplus_list, lru) {

  		if ((--needed) < 0)
  			break;

  		list_del(&page->lru);

  		/*
  		 * 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_count(page));

  		enqueue_huge_page(h, page);

  	}
  
  	/* Free unnecessary surplus pages to the buddy allocator */

  free:

  	if (!list_empty(&surplus_list)) {

  		list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
  			list_del(&page->lru);

  			put_page(page);

  		}

  	}

  	spin_lock(&hugetlb_lock);

  
  	return ret;
  }
  
  /*
   * When releasing a hugetlb pool reservation, any surplus pages that were
   * allocated to satisfy the reservation must be explicitly freed if they were
   * never used.

   * Called with hugetlb_lock held.

   */

  static void return_unused_surplus_pages(struct hstate *h,
  					unsigned long unused_resv_pages)

  {

  	unsigned long nr_pages;

  	/* Uncommit the reservation */

  	h->resv_huge_pages -= unused_resv_pages;

  	/* Cannot return gigantic pages currently */
  	if (h->order >= MAX_ORDER)
  		return;

  	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.

  	 */
  	while (nr_pages--) {

  		if (!free_pool_huge_page(h, &node_states[N_HIGH_MEMORY], 1))

  			break;

  	}
  }

  /*
   * Determine if the huge page at addr within the vma has an associated
   * reservation.  Where it does not we will need to logically increase
   * reservation and actually increase quota before an allocation can occur.
   * Where any new reservation would be required the reservation change is
   * prepared, but not committed.  Once the page has been quota'd allocated
   * an instantiated the change should be committed via vma_commit_reservation.
   * No action is required on failure.
   */

  static long vma_needs_reservation(struct hstate *h,

  			struct vm_area_struct *vma, unsigned long addr)

  {
  	struct address_space *mapping = vma->vm_file->f_mapping;
  	struct inode *inode = mapping->host;

  	if (vma->vm_flags & VM_MAYSHARE) {

  		pgoff_t idx = vma_hugecache_offset(h, vma, addr);

  		return region_chg(&inode->i_mapping->private_list,
  							idx, idx + 1);

  	} else if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
  		return 1;

  	} else  {

  		long err;

  		pgoff_t idx = vma_hugecache_offset(h, vma, addr);

  		struct resv_map *reservations = vma_resv_map(vma);
  
  		err = region_chg(&reservations->regions, idx, idx + 1);
  		if (err < 0)
  			return err;
  		return 0;
  	}

  }

  static void vma_commit_reservation(struct hstate *h,
  			struct vm_area_struct *vma, unsigned long addr)

  {
  	struct address_space *mapping = vma->vm_file->f_mapping;
  	struct inode *inode = mapping->host;

  	if (vma->vm_flags & VM_MAYSHARE) {

  		pgoff_t idx = vma_hugecache_offset(h, vma, addr);

  		region_add(&inode->i_mapping->private_list, idx, idx + 1);

  
  	} else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {

  		pgoff_t idx = vma_hugecache_offset(h, vma, addr);

  		struct resv_map *reservations = vma_resv_map(vma);
  
  		/* Mark this page used in the map. */
  		region_add(&reservations->regions, idx, idx + 1);

  	}
  }

  static struct page *alloc_huge_page(struct vm_area_struct *vma,

  				    unsigned long addr, int avoid_reserve)

  {

  	struct hstate *h = hstate_vma(vma);

  	struct page *page;

  	struct address_space *mapping = vma->vm_file->f_mapping;
  	struct inode *inode = mapping->host;

  	long chg;

  
  	/*
  	 * Processes that did not create the mapping will have no reserves and
  	 * will not have accounted against quota. Check that the quota can be
  	 * made before satisfying the allocation

  	 * MAP_NORESERVE mappings may also need pages and quota allocated
  	 * if no reserve mapping overlaps.

  	 */

  	chg = vma_needs_reservation(h, vma, addr);

  	if (chg < 0)

  		return ERR_PTR(-VM_FAULT_OOM);

  	if (chg)

  		if (hugetlb_get_quota(inode->i_mapping, chg))

  			return ERR_PTR(-VM_FAULT_SIGBUS);

  
  	spin_lock(&hugetlb_lock);

  	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve);

  	spin_unlock(&hugetlb_lock);

  	if (!page) {

  		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);

  		if (!page) {

  			hugetlb_put_quota(inode->i_mapping, chg);

  			return ERR_PTR(-VM_FAULT_SIGBUS);

  		}
  	}

  	set_page_private(page, (unsigned long) mapping);

  	vma_commit_reservation(h, vma, addr);

  	return page;

  }

  int __weak alloc_bootmem_huge_page(struct hstate *h)

  {
  	struct huge_bootmem_page *m;

  	int nr_nodes = nodes_weight(node_states[N_HIGH_MEMORY]);

  
  	while (nr_nodes) {
  		void *addr;
  
  		addr = __alloc_bootmem_node_nopanic(

  				NODE_DATA(hstate_next_node_to_alloc(h,

  						&node_states[N_HIGH_MEMORY])),

  				huge_page_size(h), huge_page_size(h), 0);
  
  		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;

  		}

  		nr_nodes--;
  	}
  	return 0;
  
  found:
  	BUG_ON((unsigned long)virt_to_phys(m) & (huge_page_size(h) - 1));
  	/* Put them into a private list first because mem_map is not up yet */
  	list_add(&m->list, &huge_boot_pages);
  	m->hstate = h;
  	return 1;
  }

  static void prep_compound_huge_page(struct page *page, 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;
  		__ClearPageReserved(page);
  		WARN_ON(page_count(page) != 1);

  		prep_compound_huge_page(page, h->order);

  		prep_new_huge_page(h, page, page_to_nid(page));

  		/*
  		 * 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 (h->order > (MAX_ORDER - 1))
  			totalram_pages += 1 << h->order;

  	}
  }

  static void __init hugetlb_hstate_alloc_pages(struct hstate *h)

  {
  	unsigned long i;

  	for (i = 0; i < h->max_huge_pages; ++i) {

  		if (h->order >= MAX_ORDER) {
  			if (!alloc_bootmem_huge_page(h))
  				break;

  		} else if (!alloc_fresh_huge_page(h,
  					 &node_states[N_HIGH_MEMORY]))

  			break;

  	}

  	h->max_huge_pages = i;

  }
  
  static void __init hugetlb_init_hstates(void)
  {
  	struct hstate *h;
  
  	for_each_hstate(h) {

  		/* oversize hugepages were init'ed in early boot */
  		if (h->order < MAX_ORDER)
  			hugetlb_hstate_alloc_pages(h);

  	}
  }

  static char * __init memfmt(char *buf, unsigned long n)
  {
  	if (n >= (1UL << 30))
  		sprintf(buf, "%lu GB", n >> 30);
  	else if (n >= (1UL << 20))
  		sprintf(buf, "%lu MB", n >> 20);
  	else
  		sprintf(buf, "%lu KB", n >> 10);
  	return buf;
  }

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

  		char buf[32];
  		printk(KERN_INFO "HugeTLB registered %s page size, "
  				 "pre-allocated %ld pages
  ",
  			memfmt(buf, huge_page_size(h)),
  			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 (h->order >= MAX_ORDER)
  		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 start_nid, next_nid;

  	int ret = 0;
  
  	VM_BUG_ON(delta != -1 && delta != 1);

  	if (delta < 0)

  		start_nid = hstate_next_node_to_alloc(h, nodes_allowed);

  	else

  		start_nid = hstate_next_node_to_free(h, nodes_allowed);

  	next_nid = start_nid;
  
  	do {
  		int nid = next_nid;
  		if (delta < 0)  {

  			/*
  			 * To shrink on this node, there must be a surplus page
  			 */

  			if (!h->surplus_huge_pages_node[nid]) {

  				next_nid = hstate_next_node_to_alloc(h,
  								nodes_allowed);

  				continue;

  			}

  		}
  		if (delta > 0) {

  			/*
  			 * Surplus cannot exceed the total number of pages
  			 */
  			if (h->surplus_huge_pages_node[nid] >=

  						h->nr_huge_pages_node[nid]) {

  				next_nid = hstate_next_node_to_free(h,
  								nodes_allowed);

  				continue;

  			}

  		}

  
  		h->surplus_huge_pages += delta;
  		h->surplus_huge_pages_node[nid] += delta;
  		ret = 1;
  		break;

  	} while (next_nid != start_nid);

  	return ret;
  }

  #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 (h->order >= MAX_ORDER)
  		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_buddy_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);

  		ret = alloc_fresh_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_buddy_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;

  	}

  	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
  ", nr_huge_pages);

  }

  static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
  			struct kobject *kobj, struct kobj_attribute *attr,
  			const char *buf, size_t len)

  {
  	int err;

  	int nid;

  	unsigned long count;

  	struct hstate *h;

  	NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);

  	err = strict_strtoul(buf, 10, &count);

  	if (err)

  		goto out;

  	h = kobj_to_hstate(kobj, &nid);

  	if (h->order >= MAX_ORDER) {
  		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_HIGH_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_HIGH_MEMORY];

  	h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);

  	if (nodes_allowed != &node_states[N_HIGH_MEMORY])

  		NODEMASK_FREE(nodes_allowed);
  
  	return len;

  out:
  	NODEMASK_FREE(nodes_allowed);
  	return err;

  }
  
  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, attr, 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, attr, 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
  ", 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 (h->order >= MAX_ORDER)
  		return -EINVAL;

  	err = strict_strtoul(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
  ", 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
  ", 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
  ", 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 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,
  				    struct attribute_group *hstate_attr_group)

  {
  	int retval;

  	int hi = h - hstates;

  	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)
  			printk(KERN_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 sysdevs in node_devices[] using a parallel array.  The array
   * index of a node sysdev or _hstate == node id.
   * This is here to avoid any static dependency of the node sysdev driver, in
   * the base kernel, on the hugetlb module.
   */
  struct node_hstate {
  	struct kobject		*hugepages_kobj;
  	struct kobject		*hstate_kobjs[HUGE_MAX_HSTATE];
  };
  struct node_hstate node_hstates[MAX_NUMNODES];
  
  /*
   * A subset of global hstate attributes for node sysdevs
   */
  static struct attribute *per_node_hstate_attrs[] = {
  	&nr_hugepages_attr.attr,
  	&free_hugepages_attr.attr,
  	&surplus_hugepages_attr.attr,
  	NULL,
  };
  
  static struct attribute_group per_node_hstate_attr_group = {
  	.attrs = per_node_hstate_attrs,
  };
  
  /*
   * kobj_to_node_hstate - lookup global hstate for node sysdev 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 sysdev.
   * No-op if no hstate attributes attached.
   */
  void hugetlb_unregister_node(struct node *node)
  {
  	struct hstate *h;
  	struct node_hstate *nhs = &node_hstates[node->sysdev.id];
  
  	if (!nhs->hugepages_kobj)

  		return;		/* no hstate attributes */

  
  	for_each_hstate(h)
  		if (nhs->hstate_kobjs[h - hstates]) {
  			kobject_put(nhs->hstate_kobjs[h - hstates]);
  			nhs->hstate_kobjs[h - hstates] = NULL;
  		}
  
  	kobject_put(nhs->hugepages_kobj);
  	nhs->hugepages_kobj = NULL;
  }
  
  /*
   * hugetlb module exit:  unregister hstate attributes from node sysdevs
   * that have them.
   */
  static void hugetlb_unregister_all_nodes(void)
  {
  	int nid;
  
  	/*
  	 * disable node sysdev registrations.
  	 */
  	register_hugetlbfs_with_node(NULL, NULL);
  
  	/*
  	 * remove hstate attributes from any nodes that have them.
  	 */
  	for (nid = 0; nid < nr_node_ids; nid++)
  		hugetlb_unregister_node(&node_devices[nid]);
  }
  
  /*
   * Register hstate attributes for a single node sysdev.
   * No-op if attributes already registered.
   */
  void hugetlb_register_node(struct node *node)
  {
  	struct hstate *h;
  	struct node_hstate *nhs = &node_hstates[node->sysdev.id];
  	int err;
  
  	if (nhs->hugepages_kobj)
  		return;		/* already allocated */
  
  	nhs->hugepages_kobj = kobject_create_and_add("hugepages",
  							&node->sysdev.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) {
  			printk(KERN_ERR "Hugetlb: Unable to add hstate %s"
  					" for node %d
  ",
  						h->name, node->sysdev.id);
  			hugetlb_unregister_node(node);
  			break;
  		}
  	}
  }
  
  /*

   * hugetlb init time:  register hstate attributes for all registered node
   * sysdevs of nodes that have memory.  All on-line nodes should have
   * registered their associated sysdev by this time.

   */
  static void hugetlb_register_all_nodes(void)
  {
  	int nid;

  	for_each_node_state(nid, N_HIGH_MEMORY) {

  		struct node *node = &node_devices[nid];
  		if (node->sysdev.id == nid)
  			hugetlb_register_node(node);
  	}
  
  	/*
  	 * Let the node sysdev 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_unregister_all_nodes(void) { }
  
  static void hugetlb_register_all_nodes(void) { }
  
  #endif

  static void __exit hugetlb_exit(void)
  {
  	struct hstate *h;

  	hugetlb_unregister_all_nodes();

  	for_each_hstate(h) {
  		kobject_put(hstate_kobjs[h - hstates]);
  	}
  
  	kobject_put(hugepages_kobj);
  }
  module_exit(hugetlb_exit);
  
  static int __init hugetlb_init(void)
  {

  	/* Some platform decide whether they support huge pages at boot
  	 * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when
  	 * there is no such support
  	 */
  	if (HPAGE_SHIFT == 0)
  		return 0;

  	if (!size_to_hstate(default_hstate_size)) {
  		default_hstate_size = HPAGE_SIZE;
  		if (!size_to_hstate(default_hstate_size))
  			hugetlb_add_hstate(HUGETLB_PAGE_ORDER);

  	}

  	default_hstate_idx = size_to_hstate(default_hstate_size) - hstates;
  	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();

  	return 0;
  }
  module_init(hugetlb_init);
  
  /* Should be called on processing a hugepagesz=... option */
  void __init hugetlb_add_hstate(unsigned order)
  {
  	struct hstate *h;

  	unsigned long i;

  	if (size_to_hstate(PAGE_SIZE << order)) {
  		printk(KERN_WARNING "hugepagesz= specified twice, ignoring
  ");
  		return;
  	}
  	BUG_ON(max_hstate >= HUGE_MAX_HSTATE);
  	BUG_ON(order == 0);
  	h = &hstates[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]);

  	h->next_nid_to_alloc = first_node(node_states[N_HIGH_MEMORY]);
  	h->next_nid_to_free = first_node(node_states[N_HIGH_MEMORY]);

  	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;

  
  	/*
  	 * !max_hstate means we haven't parsed a hugepagesz= parameter yet,
  	 * so this hugepages= parameter goes to the "default hstate".
  	 */
  	if (!max_hstate)
  		mhp = &default_hstate_max_huge_pages;
  	else
  		mhp = &parsed_hstate->max_huge_pages;

  	if (mhp == last_mhp) {
  		printk(KERN_WARNING "hugepages= specified twice without "
  			"interleaving hugepagesz=, ignoring
  ");
  		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 (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;

  	int ret;

  	tmp = h->max_huge_pages;

  	if (write && h->order >= MAX_ORDER)
  		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) {

  		NODEMASK_ALLOC(nodemask_t, nodes_allowed,
  						GFP_KERNEL | __GFP_NORETRY);

  		if (!(obey_mempolicy &&
  			       init_nodemask_of_mempolicy(nodes_allowed))) {
  			NODEMASK_FREE(nodes_allowed);
  			nodes_allowed = &node_states[N_HIGH_MEMORY];
  		}
  		h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);
  
  		if (nodes_allowed != &node_states[N_HIGH_MEMORY])
  			NODEMASK_FREE(nodes_allowed);
  	}

  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_treat_movable_handler(struct ctl_table *table, int write,

  			void __user *buffer,

  			size_t *length, loff_t *ppos)
  {

  	proc_dointvec(table, write, buffer, length, ppos);

  	if (hugepages_treat_as_movable)
  		htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
  	else
  		htlb_alloc_mask = GFP_HIGHUSER;
  	return 0;
  }

  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;

  	tmp = h->nr_overcommit_huge_pages;

  	if (write && h->order >= MAX_ORDER)
  		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 = &default_hstate;

  	seq_printf(m,

  			"HugePages_Total:   %5lu
  "
  			"HugePages_Free:    %5lu
  "
  			"HugePages_Rsvd:    %5lu
  "
  			"HugePages_Surp:    %5lu
  "
  			"Hugepagesize:   %8lu kB
  ",

  			h->nr_huge_pages,
  			h->free_huge_pages,
  			h->resv_huge_pages,
  			h->surplus_huge_pages,
  			1UL << (huge_page_order(h) + PAGE_SHIFT - 10));

  }
  
  int hugetlb_report_node_meminfo(int nid, char *buf)
  {

  	struct hstate *h = &default_hstate;

  	return sprintf(buf,
  		"Node %d HugePages_Total: %5u
  "

  		"Node %d HugePages_Free:  %5u
  "
  		"Node %d HugePages_Surp:  %5u
  ",

  		nid, h->nr_huge_pages_node[nid],
  		nid, h->free_huge_pages_node[nid],
  		nid, h->surplus_huge_pages_node[nid]);

  }

  /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
  unsigned long hugetlb_total_pages(void)
  {

  	struct hstate *h = &default_hstate;
  	return h->nr_huge_pages * pages_per_huge_page(h);

  }

  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 *reservations = 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