// SPDX-License-Identifier: GPL-2.0-only

  /*

   *  Copyright (C) 1993  Linus Torvalds
   *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
   *  SMP-safe vmalloc/vfree/ioremap, Tigran Aivazian <tigran@veritas.com>, May 2000
   *  Major rework to support vmap/vunmap, Christoph Hellwig, SGI, August 2002

   *  Numa awareness, Christoph Lameter, SGI, June 2005

   *  Improving global KVA allocator, Uladzislau Rezki, Sony, May 2019

   */

  #include <linux/vmalloc.h>

  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/highmem.h>

  #include <linux/sched/signal.h>

  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/interrupt.h>

  #include <linux/proc_fs.h>

  #include <linux/seq_file.h>

  #include <linux/set_memory.h>

  #include <linux/debugobjects.h>

  #include <linux/kallsyms.h>

  #include <linux/list.h>

  #include <linux/notifier.h>

  #include <linux/rbtree.h>

  #include <linux/xarray.h>

  #include <linux/rcupdate.h>

  #include <linux/pfn.h>

  #include <linux/kmemleak.h>

  #include <linux/atomic.h>

  #include <linux/compiler.h>

  #include <linux/llist.h>

  #include <linux/bitops.h>

  #include <linux/rbtree_augmented.h>

  #include <linux/overflow.h>

  #include <linux/uaccess.h>

  #include <asm/tlbflush.h>

  #include <asm/shmparam.h>

  #include "internal.h"

  #include "pgalloc-track.h"

  bool is_vmalloc_addr(const void *x)
  {
  	unsigned long addr = (unsigned long)x;
  
  	return addr >= VMALLOC_START && addr < VMALLOC_END;
  }
  EXPORT_SYMBOL(is_vmalloc_addr);

  struct vfree_deferred {
  	struct llist_head list;
  	struct work_struct wq;
  };
  static DEFINE_PER_CPU(struct vfree_deferred, vfree_deferred);
  
  static void __vunmap(const void *, int);
  
  static void free_work(struct work_struct *w)
  {
  	struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);

  	struct llist_node *t, *llnode;
  
  	llist_for_each_safe(llnode, t, llist_del_all(&p->list))
  		__vunmap((void *)llnode, 1);

  }

  /*** Page table manipulation functions ***/

  static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
  			     pgtbl_mod_mask *mask)

  {
  	pte_t *pte;
  
  	pte = pte_offset_kernel(pmd, addr);
  	do {
  		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
  		WARN_ON(!pte_none(ptent) && !pte_present(ptent));
  	} while (pte++, addr += PAGE_SIZE, addr != end);

  	*mask |= PGTBL_PTE_MODIFIED;

  }

  static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
  			     pgtbl_mod_mask *mask)

  {
  	pmd_t *pmd;
  	unsigned long next;

  	int cleared;

  
  	pmd = pmd_offset(pud, addr);
  	do {
  		next = pmd_addr_end(addr, end);

  
  		cleared = pmd_clear_huge(pmd);
  		if (cleared || pmd_bad(*pmd))
  			*mask |= PGTBL_PMD_MODIFIED;
  
  		if (cleared)

  			continue;

  		if (pmd_none_or_clear_bad(pmd))
  			continue;

  		vunmap_pte_range(pmd, addr, next, mask);

  
  		cond_resched();

  	} while (pmd++, addr = next, addr != end);
  }

  static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
  			     pgtbl_mod_mask *mask)

  {
  	pud_t *pud;
  	unsigned long next;

  	int cleared;

  	pud = pud_offset(p4d, addr);

  	do {
  		next = pud_addr_end(addr, end);

  
  		cleared = pud_clear_huge(pud);
  		if (cleared || pud_bad(*pud))
  			*mask |= PGTBL_PUD_MODIFIED;
  
  		if (cleared)

  			continue;

  		if (pud_none_or_clear_bad(pud))
  			continue;

  		vunmap_pmd_range(pud, addr, next, mask);

  	} while (pud++, addr = next, addr != end);
  }

  static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
  			     pgtbl_mod_mask *mask)

  {
  	p4d_t *p4d;
  	unsigned long next;

  	int cleared;

  
  	p4d = p4d_offset(pgd, addr);
  	do {
  		next = p4d_addr_end(addr, end);

  
  		cleared = p4d_clear_huge(p4d);
  		if (cleared || p4d_bad(*p4d))
  			*mask |= PGTBL_P4D_MODIFIED;
  
  		if (cleared)

  			continue;
  		if (p4d_none_or_clear_bad(p4d))
  			continue;

  		vunmap_pud_range(p4d, addr, next, mask);

  	} while (p4d++, addr = next, addr != end);
  }

  /**
   * unmap_kernel_range_noflush - unmap kernel VM area

   * @start: start of the VM area to unmap

   * @size: size of the VM area to unmap
   *
   * Unmap PFN_UP(@size) pages at @addr.  The VM area @addr and @size specify
   * should have been allocated using get_vm_area() and its friends.
   *
   * NOTE:
   * This function does NOT do any cache flushing.  The caller is responsible
   * for calling flush_cache_vunmap() on to-be-mapped areas before calling this
   * function and flush_tlb_kernel_range() after.
   */

  void unmap_kernel_range_noflush(unsigned long start, unsigned long size)

  {

  	unsigned long end = start + size;

  	unsigned long next;

  	pgd_t *pgd;

  	unsigned long addr = start;
  	pgtbl_mod_mask mask = 0;

  
  	BUG_ON(addr >= end);
  	pgd = pgd_offset_k(addr);

  	do {
  		next = pgd_addr_end(addr, end);

  		if (pgd_bad(*pgd))
  			mask |= PGTBL_PGD_MODIFIED;

  		if (pgd_none_or_clear_bad(pgd))
  			continue;

  		vunmap_p4d_range(pgd, addr, next, &mask);

  	} while (pgd++, addr = next, addr != end);

  
  	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
  		arch_sync_kernel_mappings(start, end);

  }
  
  static int vmap_pte_range(pmd_t *pmd, unsigned long addr,

  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
  		pgtbl_mod_mask *mask)

  {
  	pte_t *pte;

  	/*
  	 * nr is a running index into the array which helps higher level
  	 * callers keep track of where we're up to.
  	 */

  	pte = pte_alloc_kernel_track(pmd, addr, mask);

  	if (!pte)
  		return -ENOMEM;
  	do {

  		struct page *page = pages[*nr];
  
  		if (WARN_ON(!pte_none(*pte)))
  			return -EBUSY;
  		if (WARN_ON(!page))

  			return -ENOMEM;
  		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));

  		(*nr)++;

  	} while (pte++, addr += PAGE_SIZE, addr != end);

  	*mask |= PGTBL_PTE_MODIFIED;

  	return 0;
  }

  static int vmap_pmd_range(pud_t *pud, unsigned long addr,

  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
  		pgtbl_mod_mask *mask)

  {
  	pmd_t *pmd;
  	unsigned long next;

  	pmd = pmd_alloc_track(&init_mm, pud, addr, mask);

  	if (!pmd)
  		return -ENOMEM;
  	do {
  		next = pmd_addr_end(addr, end);

  		if (vmap_pte_range(pmd, addr, next, prot, pages, nr, mask))

  			return -ENOMEM;
  	} while (pmd++, addr = next, addr != end);
  	return 0;
  }

  static int vmap_pud_range(p4d_t *p4d, unsigned long addr,

  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
  		pgtbl_mod_mask *mask)

  {
  	pud_t *pud;
  	unsigned long next;

  	pud = pud_alloc_track(&init_mm, p4d, addr, mask);

  	if (!pud)
  		return -ENOMEM;
  	do {
  		next = pud_addr_end(addr, end);

  		if (vmap_pmd_range(pud, addr, next, prot, pages, nr, mask))

  			return -ENOMEM;
  	} while (pud++, addr = next, addr != end);
  	return 0;
  }

  static int vmap_p4d_range(pgd_t *pgd, unsigned long addr,

  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
  		pgtbl_mod_mask *mask)

  {
  	p4d_t *p4d;
  	unsigned long next;

  	p4d = p4d_alloc_track(&init_mm, pgd, addr, mask);

  	if (!p4d)
  		return -ENOMEM;
  	do {
  		next = p4d_addr_end(addr, end);

  		if (vmap_pud_range(p4d, addr, next, prot, pages, nr, mask))

  			return -ENOMEM;
  	} while (p4d++, addr = next, addr != end);
  	return 0;
  }

  /**
   * map_kernel_range_noflush - map kernel VM area with the specified pages
   * @addr: start of the VM area to map
   * @size: size of the VM area to map
   * @prot: page protection flags to use
   * @pages: pages to map

   *

   * Map PFN_UP(@size) pages at @addr.  The VM area @addr and @size specify should
   * have been allocated using get_vm_area() and its friends.
   *
   * NOTE:
   * This function does NOT do any cache flushing.  The caller is responsible for
   * calling flush_cache_vmap() on to-be-mapped areas before calling this
   * function.
   *
   * RETURNS:

   * 0 on success, -errno on failure.

   */

  int map_kernel_range_noflush(unsigned long addr, unsigned long size,
  			     pgprot_t prot, struct page **pages)

  {

  	unsigned long start = addr;

  	unsigned long end = addr + size;

  	unsigned long next;

  	pgd_t *pgd;

  	int err = 0;
  	int nr = 0;

  	pgtbl_mod_mask mask = 0;

  
  	BUG_ON(addr >= end);
  	pgd = pgd_offset_k(addr);

  	do {
  		next = pgd_addr_end(addr, end);

  		if (pgd_bad(*pgd))
  			mask |= PGTBL_PGD_MODIFIED;
  		err = vmap_p4d_range(pgd, addr, next, prot, pages, &nr, &mask);

  		if (err)

  			return err;

  	} while (pgd++, addr = next, addr != end);

  	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
  		arch_sync_kernel_mappings(start, end);

  	return 0;

  }

  int map_kernel_range(unsigned long start, unsigned long size, pgprot_t prot,
  		struct page **pages)

  {
  	int ret;

  	ret = map_kernel_range_noflush(start, size, prot, pages);
  	flush_cache_vmap(start, start + size);

  	return ret;
  }

  int is_vmalloc_or_module_addr(const void *x)

  {
  	/*

  	 * ARM, x86-64 and sparc64 put modules in a special place,

  	 * and fall back on vmalloc() if that fails. Others
  	 * just put it in the vmalloc space.
  	 */
  #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
  	unsigned long addr = (unsigned long)x;
  	if (addr >= MODULES_VADDR && addr < MODULES_END)
  		return 1;
  #endif
  	return is_vmalloc_addr(x);
  }

  /*

   * Walk a vmap address to the struct page it maps.

   */

  struct page *vmalloc_to_page(const void *vmalloc_addr)

  {
  	unsigned long addr = (unsigned long) vmalloc_addr;

  	struct page *page = NULL;

  	pgd_t *pgd = pgd_offset_k(addr);

  	p4d_t *p4d;
  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *ptep, pte;

  	/*
  	 * XXX we might need to change this if we add VIRTUAL_BUG_ON for
  	 * architectures that do not vmalloc module space
  	 */

  	VIRTUAL_BUG_ON(!is_vmalloc_or_module_addr(vmalloc_addr));

  	if (pgd_none(*pgd))
  		return NULL;
  	p4d = p4d_offset(pgd, addr);
  	if (p4d_none(*p4d))
  		return NULL;
  	pud = pud_offset(p4d, addr);

  
  	/*
  	 * Don't dereference bad PUD or PMD (below) entries. This will also
  	 * identify huge mappings, which we may encounter on architectures
  	 * that define CONFIG_HAVE_ARCH_HUGE_VMAP=y. Such regions will be
  	 * identified as vmalloc addresses by is_vmalloc_addr(), but are
  	 * not [unambiguously] associated with a struct page, so there is
  	 * no correct value to return for them.
  	 */
  	WARN_ON_ONCE(pud_bad(*pud));
  	if (pud_none(*pud) || pud_bad(*pud))

  		return NULL;
  	pmd = pmd_offset(pud, addr);

  	WARN_ON_ONCE(pmd_bad(*pmd));
  	if (pmd_none(*pmd) || pmd_bad(*pmd))

  		return NULL;
  
  	ptep = pte_offset_map(pmd, addr);
  	pte = *ptep;
  	if (pte_present(pte))
  		page = pte_page(pte);
  	pte_unmap(ptep);

  	return page;

  }

  EXPORT_SYMBOL(vmalloc_to_page);

  
  /*

   * Map a vmalloc()-space virtual address to the physical page frame number.

   */

  unsigned long vmalloc_to_pfn(const void *vmalloc_addr)

  {

  	return page_to_pfn(vmalloc_to_page(vmalloc_addr));

  }

  EXPORT_SYMBOL(vmalloc_to_pfn);

  
  /*** Global kva allocator ***/

  #define DEBUG_AUGMENT_PROPAGATE_CHECK 0

  #define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0

  static DEFINE_SPINLOCK(vmap_area_lock);

  static DEFINE_SPINLOCK(free_vmap_area_lock);

  /* Export for kexec only */
  LIST_HEAD(vmap_area_list);

  static LLIST_HEAD(vmap_purge_list);

  static struct rb_root vmap_area_root = RB_ROOT;

  static bool vmap_initialized __read_mostly;

  /*
   * This kmem_cache is used for vmap_area objects. Instead of
   * allocating from slab we reuse an object from this cache to
   * make things faster. Especially in "no edge" splitting of
   * free block.
   */
  static struct kmem_cache *vmap_area_cachep;
  
  /*
   * This linked list is used in pair with free_vmap_area_root.
   * It gives O(1) access to prev/next to perform fast coalescing.
   */
  static LIST_HEAD(free_vmap_area_list);
  
  /*
   * This augment red-black tree represents the free vmap space.
   * All vmap_area objects in this tree are sorted by va->va_start
   * address. It is used for allocation and merging when a vmap
   * object is released.
   *
   * Each vmap_area node contains a maximum available free block
   * of its sub-tree, right or left. Therefore it is possible to
   * find a lowest match of free area.
   */
  static struct rb_root free_vmap_area_root = RB_ROOT;

  /*
   * Preload a CPU with one object for "no edge" split case. The
   * aim is to get rid of allocations from the atomic context, thus
   * to use more permissive allocation masks.
   */
  static DEFINE_PER_CPU(struct vmap_area *, ne_fit_preload_node);

  static __always_inline unsigned long
  va_size(struct vmap_area *va)
  {
  	return (va->va_end - va->va_start);
  }
  
  static __always_inline unsigned long
  get_subtree_max_size(struct rb_node *node)
  {
  	struct vmap_area *va;
  
  	va = rb_entry_safe(node, struct vmap_area, rb_node);
  	return va ? va->subtree_max_size : 0;
  }

  /*
   * Gets called when remove the node and rotate.
   */
  static __always_inline unsigned long
  compute_subtree_max_size(struct vmap_area *va)
  {
  	return max3(va_size(va),
  		get_subtree_max_size(va->rb_node.rb_left),
  		get_subtree_max_size(va->rb_node.rb_right));
  }

  RB_DECLARE_CALLBACKS_MAX(static, free_vmap_area_rb_augment_cb,
  	struct vmap_area, rb_node, unsigned long, subtree_max_size, va_size)

  
  static void purge_vmap_area_lazy(void);
  static BLOCKING_NOTIFIER_HEAD(vmap_notify_list);
  static unsigned long lazy_max_pages(void);

  static atomic_long_t nr_vmalloc_pages;
  
  unsigned long vmalloc_nr_pages(void)
  {
  	return atomic_long_read(&nr_vmalloc_pages);
  }

  EXPORT_SYMBOL_GPL(vmalloc_nr_pages);

  static struct vmap_area *__find_vmap_area(unsigned long addr)

  {

  	struct rb_node *n = vmap_area_root.rb_node;
  
  	while (n) {
  		struct vmap_area *va;
  
  		va = rb_entry(n, struct vmap_area, rb_node);
  		if (addr < va->va_start)
  			n = n->rb_left;

  		else if (addr >= va->va_end)

  			n = n->rb_right;
  		else
  			return va;
  	}
  
  	return NULL;
  }

  /*
   * This function returns back addresses of parent node
   * and its left or right link for further processing.

   *
   * Otherwise NULL is returned. In that case all further
   * steps regarding inserting of conflicting overlap range
   * have to be declined and actually considered as a bug.

   */
  static __always_inline struct rb_node **
  find_va_links(struct vmap_area *va,
  	struct rb_root *root, struct rb_node *from,
  	struct rb_node **parent)
  {
  	struct vmap_area *tmp_va;
  	struct rb_node **link;
  
  	if (root) {
  		link = &root->rb_node;
  		if (unlikely(!*link)) {
  			*parent = NULL;
  			return link;
  		}
  	} else {
  		link = &from;
  	}

  	/*
  	 * Go to the bottom of the tree. When we hit the last point
  	 * we end up with parent rb_node and correct direction, i name
  	 * it link, where the new va->rb_node will be attached to.
  	 */
  	do {
  		tmp_va = rb_entry(*link, struct vmap_area, rb_node);

  		/*
  		 * During the traversal we also do some sanity check.
  		 * Trigger the BUG() if there are sides(left/right)
  		 * or full overlaps.
  		 */
  		if (va->va_start < tmp_va->va_end &&
  				va->va_end <= tmp_va->va_start)
  			link = &(*link)->rb_left;
  		else if (va->va_end > tmp_va->va_start &&
  				va->va_start >= tmp_va->va_end)
  			link = &(*link)->rb_right;

  		else {
  			WARN(1, "vmalloc bug: 0x%lx-0x%lx overlaps with 0x%lx-0x%lx
  ",
  				va->va_start, va->va_end, tmp_va->va_start, tmp_va->va_end);
  
  			return NULL;
  		}

  	} while (*link);
  
  	*parent = &tmp_va->rb_node;
  	return link;
  }
  
  static __always_inline struct list_head *
  get_va_next_sibling(struct rb_node *parent, struct rb_node **link)
  {
  	struct list_head *list;
  
  	if (unlikely(!parent))
  		/*
  		 * The red-black tree where we try to find VA neighbors
  		 * before merging or inserting is empty, i.e. it means
  		 * there is no free vmap space. Normally it does not
  		 * happen but we handle this case anyway.
  		 */
  		return NULL;
  
  	list = &rb_entry(parent, struct vmap_area, rb_node)->list;
  	return (&parent->rb_right == link ? list->next : list);
  }
  
  static __always_inline void
  link_va(struct vmap_area *va, struct rb_root *root,
  	struct rb_node *parent, struct rb_node **link, struct list_head *head)
  {
  	/*
  	 * VA is still not in the list, but we can
  	 * identify its future previous list_head node.
  	 */
  	if (likely(parent)) {
  		head = &rb_entry(parent, struct vmap_area, rb_node)->list;
  		if (&parent->rb_right != link)
  			head = head->prev;

  	}

  	/* Insert to the rb-tree */
  	rb_link_node(&va->rb_node, parent, link);
  	if (root == &free_vmap_area_root) {
  		/*
  		 * Some explanation here. Just perform simple insertion
  		 * to the tree. We do not set va->subtree_max_size to
  		 * its current size before calling rb_insert_augmented().
  		 * It is because of we populate the tree from the bottom
  		 * to parent levels when the node _is_ in the tree.
  		 *
  		 * Therefore we set subtree_max_size to zero after insertion,
  		 * to let __augment_tree_propagate_from() puts everything to
  		 * the correct order later on.
  		 */
  		rb_insert_augmented(&va->rb_node,
  			root, &free_vmap_area_rb_augment_cb);
  		va->subtree_max_size = 0;
  	} else {
  		rb_insert_color(&va->rb_node, root);
  	}

  	/* Address-sort this list */
  	list_add(&va->list, head);

  }

  static __always_inline void
  unlink_va(struct vmap_area *va, struct rb_root *root)
  {

  	if (WARN_ON(RB_EMPTY_NODE(&va->rb_node)))
  		return;

  	if (root == &free_vmap_area_root)
  		rb_erase_augmented(&va->rb_node,
  			root, &free_vmap_area_rb_augment_cb);
  	else
  		rb_erase(&va->rb_node, root);
  
  	list_del(&va->list);
  	RB_CLEAR_NODE(&va->rb_node);

  }

  #if DEBUG_AUGMENT_PROPAGATE_CHECK
  static void

  augment_tree_propagate_check(void)

  {
  	struct vmap_area *va;

  	unsigned long computed_size;

  	list_for_each_entry(va, &free_vmap_area_list, list) {
  		computed_size = compute_subtree_max_size(va);
  		if (computed_size != va->subtree_max_size)
  			pr_emerg("tree is corrupted: %lu, %lu
  ",
  				va_size(va), va->subtree_max_size);

  	}

  }
  #endif

  /*
   * This function populates subtree_max_size from bottom to upper
   * levels starting from VA point. The propagation must be done
   * when VA size is modified by changing its va_start/va_end. Or
   * in case of newly inserting of VA to the tree.
   *
   * It means that __augment_tree_propagate_from() must be called:
   * - After VA has been inserted to the tree(free path);
   * - After VA has been shrunk(allocation path);
   * - After VA has been increased(merging path).
   *
   * Please note that, it does not mean that upper parent nodes
   * and their subtree_max_size are recalculated all the time up
   * to the root node.
   *
   *       4--8
   *        /\
   *       /  \
   *      /    \
   *    2--2  8--8
   *
   * For example if we modify the node 4, shrinking it to 2, then
   * no any modification is required. If we shrink the node 2 to 1
   * its subtree_max_size is updated only, and set to 1. If we shrink
   * the node 8 to 6, then its subtree_max_size is set to 6 and parent
   * node becomes 4--6.
   */
  static __always_inline void
  augment_tree_propagate_from(struct vmap_area *va)
  {

  	/*
  	 * Populate the tree from bottom towards the root until
  	 * the calculated maximum available size of checked node
  	 * is equal to its current one.
  	 */
  	free_vmap_area_rb_augment_cb_propagate(&va->rb_node, NULL);

  
  #if DEBUG_AUGMENT_PROPAGATE_CHECK

  	augment_tree_propagate_check();

  #endif

  }
  
  static void
  insert_vmap_area(struct vmap_area *va,
  	struct rb_root *root, struct list_head *head)
  {
  	struct rb_node **link;
  	struct rb_node *parent;
  
  	link = find_va_links(va, root, NULL, &parent);

  	if (link)
  		link_va(va, root, parent, link, head);

  }
  
  static void
  insert_vmap_area_augment(struct vmap_area *va,
  	struct rb_node *from, struct rb_root *root,
  	struct list_head *head)
  {
  	struct rb_node **link;
  	struct rb_node *parent;
  
  	if (from)
  		link = find_va_links(va, NULL, from, &parent);
  	else
  		link = find_va_links(va, root, NULL, &parent);

  	if (link) {
  		link_va(va, root, parent, link, head);
  		augment_tree_propagate_from(va);
  	}

  }
  
  /*
   * Merge de-allocated chunk of VA memory with previous
   * and next free blocks. If coalesce is not done a new
   * free area is inserted. If VA has been merged, it is
   * freed.

   *
   * Please note, it can return NULL in case of overlap
   * ranges, followed by WARN() report. Despite it is a
   * buggy behaviour, a system can be alive and keep
   * ongoing.

   */

  static __always_inline struct vmap_area *

  merge_or_add_vmap_area(struct vmap_area *va,
  	struct rb_root *root, struct list_head *head)
  {
  	struct vmap_area *sibling;
  	struct list_head *next;
  	struct rb_node **link;
  	struct rb_node *parent;
  	bool merged = false;
  
  	/*
  	 * Find a place in the tree where VA potentially will be
  	 * inserted, unless it is merged with its sibling/siblings.
  	 */
  	link = find_va_links(va, root, NULL, &parent);

  	if (!link)
  		return NULL;

  
  	/*
  	 * Get next node of VA to check if merging can be done.
  	 */
  	next = get_va_next_sibling(parent, link);
  	if (unlikely(next == NULL))
  		goto insert;
  
  	/*
  	 * start            end
  	 * |                |
  	 * |<------VA------>|<-----Next----->|
  	 *                  |                |
  	 *                  start            end
  	 */
  	if (next != head) {
  		sibling = list_entry(next, struct vmap_area, list);
  		if (sibling->va_start == va->va_end) {
  			sibling->va_start = va->va_start;

  			/* Free vmap_area object. */
  			kmem_cache_free(vmap_area_cachep, va);
  
  			/* Point to the new merged area. */
  			va = sibling;
  			merged = true;
  		}
  	}
  
  	/*
  	 * start            end
  	 * |                |
  	 * |<-----Prev----->|<------VA------>|
  	 *                  |                |
  	 *                  start            end
  	 */
  	if (next->prev != head) {
  		sibling = list_entry(next->prev, struct vmap_area, list);
  		if (sibling->va_end == va->va_start) {

  			/*
  			 * If both neighbors are coalesced, it is important
  			 * to unlink the "next" node first, followed by merging
  			 * with "previous" one. Otherwise the tree might not be
  			 * fully populated if a sibling's augmented value is
  			 * "normalized" because of rotation operations.
  			 */

  			if (merged)
  				unlink_va(va, root);

  			sibling->va_end = va->va_end;

  			/* Free vmap_area object. */
  			kmem_cache_free(vmap_area_cachep, va);

  
  			/* Point to the new merged area. */
  			va = sibling;
  			merged = true;

  		}
  	}
  
  insert:

  	if (!merged)

  		link_va(va, root, parent, link, head);

  	/*
  	 * Last step is to check and update the tree.
  	 */
  	augment_tree_propagate_from(va);

  	return va;

  }
  
  static __always_inline bool
  is_within_this_va(struct vmap_area *va, unsigned long size,
  	unsigned long align, unsigned long vstart)
  {
  	unsigned long nva_start_addr;
  
  	if (va->va_start > vstart)
  		nva_start_addr = ALIGN(va->va_start, align);
  	else
  		nva_start_addr = ALIGN(vstart, align);
  
  	/* Can be overflowed due to big size or alignment. */
  	if (nva_start_addr + size < nva_start_addr ||
  			nva_start_addr < vstart)
  		return false;
  
  	return (nva_start_addr + size <= va->va_end);
  }
  
  /*
   * Find the first free block(lowest start address) in the tree,
   * that will accomplish the request corresponding to passing
   * parameters.
   */
  static __always_inline struct vmap_area *
  find_vmap_lowest_match(unsigned long size,
  	unsigned long align, unsigned long vstart)
  {
  	struct vmap_area *va;
  	struct rb_node *node;
  	unsigned long length;
  
  	/* Start from the root. */
  	node = free_vmap_area_root.rb_node;
  
  	/* Adjust the search size for alignment overhead. */
  	length = size + align - 1;
  
  	while (node) {
  		va = rb_entry(node, struct vmap_area, rb_node);
  
  		if (get_subtree_max_size(node->rb_left) >= length &&
  				vstart < va->va_start) {
  			node = node->rb_left;
  		} else {
  			if (is_within_this_va(va, size, align, vstart))
  				return va;
  
  			/*
  			 * Does not make sense to go deeper towards the right
  			 * sub-tree if it does not have a free block that is
  			 * equal or bigger to the requested search length.
  			 */
  			if (get_subtree_max_size(node->rb_right) >= length) {
  				node = node->rb_right;
  				continue;
  			}
  
  			/*

  			 * OK. We roll back and find the first right sub-tree,

  			 * that will satisfy the search criteria. It can happen
  			 * only once due to "vstart" restriction.
  			 */
  			while ((node = rb_parent(node))) {
  				va = rb_entry(node, struct vmap_area, rb_node);
  				if (is_within_this_va(va, size, align, vstart))
  					return va;
  
  				if (get_subtree_max_size(node->rb_right) >= length &&
  						vstart <= va->va_start) {
  					node = node->rb_right;
  					break;
  				}
  			}
  		}
  	}
  
  	return NULL;
  }

  #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
  #include <linux/random.h>
  
  static struct vmap_area *
  find_vmap_lowest_linear_match(unsigned long size,
  	unsigned long align, unsigned long vstart)
  {
  	struct vmap_area *va;
  
  	list_for_each_entry(va, &free_vmap_area_list, list) {
  		if (!is_within_this_va(va, size, align, vstart))
  			continue;
  
  		return va;
  	}
  
  	return NULL;
  }
  
  static void
  find_vmap_lowest_match_check(unsigned long size)
  {
  	struct vmap_area *va_1, *va_2;
  	unsigned long vstart;
  	unsigned int rnd;
  
  	get_random_bytes(&rnd, sizeof(rnd));
  	vstart = VMALLOC_START + rnd;
  
  	va_1 = find_vmap_lowest_match(size, 1, vstart);
  	va_2 = find_vmap_lowest_linear_match(size, 1, vstart);
  
  	if (va_1 != va_2)
  		pr_emerg("not lowest: t: 0x%p, l: 0x%p, v: 0x%lx
  ",
  			va_1, va_2, vstart);
  }
  #endif

  enum fit_type {
  	NOTHING_FIT = 0,
  	FL_FIT_TYPE = 1,	/* full fit */
  	LE_FIT_TYPE = 2,	/* left edge fit */
  	RE_FIT_TYPE = 3,	/* right edge fit */
  	NE_FIT_TYPE = 4		/* no edge fit */
  };
  
  static __always_inline enum fit_type
  classify_va_fit_type(struct vmap_area *va,
  	unsigned long nva_start_addr, unsigned long size)
  {
  	enum fit_type type;
  
  	/* Check if it is within VA. */
  	if (nva_start_addr < va->va_start ||
  			nva_start_addr + size > va->va_end)
  		return NOTHING_FIT;
  
  	/* Now classify. */
  	if (va->va_start == nva_start_addr) {
  		if (va->va_end == nva_start_addr + size)
  			type = FL_FIT_TYPE;
  		else
  			type = LE_FIT_TYPE;
  	} else if (va->va_end == nva_start_addr + size) {
  		type = RE_FIT_TYPE;
  	} else {
  		type = NE_FIT_TYPE;
  	}
  
  	return type;
  }
  
  static __always_inline int
  adjust_va_to_fit_type(struct vmap_area *va,
  	unsigned long nva_start_addr, unsigned long size,
  	enum fit_type type)
  {

  	struct vmap_area *lva = NULL;

  
  	if (type == FL_FIT_TYPE) {
  		/*
  		 * No need to split VA, it fully fits.
  		 *
  		 * |               |
  		 * V      NVA      V
  		 * |---------------|
  		 */
  		unlink_va(va, &free_vmap_area_root);
  		kmem_cache_free(vmap_area_cachep, va);
  	} else if (type == LE_FIT_TYPE) {
  		/*
  		 * Split left edge of fit VA.
  		 *
  		 * |       |
  		 * V  NVA  V   R
  		 * |-------|-------|
  		 */
  		va->va_start += size;
  	} else if (type == RE_FIT_TYPE) {
  		/*
  		 * Split right edge of fit VA.
  		 *
  		 *         |       |
  		 *     L   V  NVA  V
  		 * |-------|-------|
  		 */
  		va->va_end = nva_start_addr;
  	} else if (type == NE_FIT_TYPE) {
  		/*
  		 * Split no edge of fit VA.
  		 *
  		 *     |       |
  		 *   L V  NVA  V R
  		 * |---|-------|---|
  		 */

  		lva = __this_cpu_xchg(ne_fit_preload_node, NULL);
  		if (unlikely(!lva)) {
  			/*
  			 * For percpu allocator we do not do any pre-allocation
  			 * and leave it as it is. The reason is it most likely
  			 * never ends up with NE_FIT_TYPE splitting. In case of
  			 * percpu allocations offsets and sizes are aligned to
  			 * fixed align request, i.e. RE_FIT_TYPE and FL_FIT_TYPE
  			 * are its main fitting cases.
  			 *
  			 * There are a few exceptions though, as an example it is
  			 * a first allocation (early boot up) when we have "one"
  			 * big free space that has to be split.

  			 *
  			 * Also we can hit this path in case of regular "vmap"
  			 * allocations, if "this" current CPU was not preloaded.
  			 * See the comment in alloc_vmap_area() why. If so, then
  			 * GFP_NOWAIT is used instead to get an extra object for
  			 * split purpose. That is rare and most time does not
  			 * occur.
  			 *
  			 * What happens if an allocation gets failed. Basically,
  			 * an "overflow" path is triggered to purge lazily freed
  			 * areas to free some memory, then, the "retry" path is
  			 * triggered to repeat one more time. See more details
  			 * in alloc_vmap_area() function.

  			 */
  			lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT);
  			if (!lva)
  				return -1;
  		}

  
  		/*
  		 * Build the remainder.
  		 */
  		lva->va_start = va->va_start;
  		lva->va_end = nva_start_addr;
  
  		/*
  		 * Shrink this VA to remaining size.
  		 */
  		va->va_start = nva_start_addr + size;
  	} else {
  		return -1;
  	}
  
  	if (type != FL_FIT_TYPE) {
  		augment_tree_propagate_from(va);

  		if (lva)	/* type == NE_FIT_TYPE */

  			insert_vmap_area_augment(lva, &va->rb_node,
  				&free_vmap_area_root, &free_vmap_area_list);
  	}
  
  	return 0;
  }
  
  /*
   * Returns a start address of the newly allocated area, if success.
   * Otherwise a vend is returned that indicates failure.
   */
  static __always_inline unsigned long
  __alloc_vmap_area(unsigned long size, unsigned long align,

  	unsigned long vstart, unsigned long vend)

  {
  	unsigned long nva_start_addr;
  	struct vmap_area *va;
  	enum fit_type type;
  	int ret;
  
  	va = find_vmap_lowest_match(size, align, vstart);
  	if (unlikely(!va))
  		return vend;
  
  	if (va->va_start > vstart)
  		nva_start_addr = ALIGN(va->va_start, align);
  	else
  		nva_start_addr = ALIGN(vstart, align);
  
  	/* Check the "vend" restriction. */
  	if (nva_start_addr + size > vend)
  		return vend;
  
  	/* Classify what we have found. */
  	type = classify_va_fit_type(va, nva_start_addr, size);
  	if (WARN_ON_ONCE(type == NOTHING_FIT))
  		return vend;
  
  	/* Update the free vmap_area. */
  	ret = adjust_va_to_fit_type(va, nva_start_addr, size, type);
  	if (ret)
  		return vend;

  #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
  	find_vmap_lowest_match_check(size);
  #endif

  	return nva_start_addr;
  }

  /*

   * Free a region of KVA allocated by alloc_vmap_area
   */
  static void free_vmap_area(struct vmap_area *va)
  {
  	/*
  	 * Remove from the busy tree/list.
  	 */
  	spin_lock(&vmap_area_lock);
  	unlink_va(va, &vmap_area_root);
  	spin_unlock(&vmap_area_lock);
  
  	/*
  	 * Insert/Merge it back to the free tree/list.
  	 */
  	spin_lock(&free_vmap_area_lock);
  	merge_or_add_vmap_area(va, &free_vmap_area_root, &free_vmap_area_list);
  	spin_unlock(&free_vmap_area_lock);
  }
  
  /*

   * Allocate a region of KVA of the specified size and alignment, within the
   * vstart and vend.
   */
  static struct vmap_area *alloc_vmap_area(unsigned long size,
  				unsigned long align,
  				unsigned long vstart, unsigned long vend,
  				int node, gfp_t gfp_mask)
  {

  	struct vmap_area *va, *pva;

  	unsigned long addr;

  	int purged = 0;

  	int ret;

  	BUG_ON(!size);

  	BUG_ON(offset_in_page(size));

  	BUG_ON(!is_power_of_2(align));

  	if (unlikely(!vmap_initialized))
  		return ERR_PTR(-EBUSY);

  	might_sleep();

  	gfp_mask = gfp_mask & GFP_RECLAIM_MASK;

  	va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);

  	if (unlikely(!va))
  		return ERR_PTR(-ENOMEM);

  	/*
  	 * Only scan the relevant parts containing pointers to other objects
  	 * to avoid false negatives.
  	 */

  	kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask);

  retry:

  	/*

  	 * Preload this CPU with one extra vmap_area object. It is used
  	 * when fit type of free area is NE_FIT_TYPE. Please note, it
  	 * does not guarantee that an allocation occurs on a CPU that
  	 * is preloaded, instead we minimize the case when it is not.
  	 * It can happen because of cpu migration, because there is a
  	 * race until the below spinlock is taken.

  	 *
  	 * The preload is done in non-atomic context, thus it allows us
  	 * to use more permissive allocation masks to be more stable under

  	 * low memory condition and high memory pressure. In rare case,
  	 * if not preloaded, GFP_NOWAIT is used.

  	 *

  	 * Set "pva" to NULL here, because of "retry" path.

  	 */

  	pva = NULL;

  	if (!this_cpu_read(ne_fit_preload_node))
  		/*
  		 * Even if it fails we do not really care about that.
  		 * Just proceed as it is. If needed "overflow" path
  		 * will refill the cache we allocate from.
  		 */

  		pva = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);

  	spin_lock(&free_vmap_area_lock);

  
  	if (pva && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, pva))
  		kmem_cache_free(vmap_area_cachep, pva);

  	/*

  	 * If an allocation fails, the "vend" address is
  	 * returned. Therefore trigger the overflow path.

  	 */

  	addr = __alloc_vmap_area(size, align, vstart, vend);

  	spin_unlock(&free_vmap_area_lock);

  	if (unlikely(addr == vend))

  		goto overflow;

  
  	va->va_start = addr;
  	va->va_end = addr + size;

  	va->vm = NULL;

  	spin_lock(&vmap_area_lock);
  	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);

  	spin_unlock(&vmap_area_lock);

  	BUG_ON(!IS_ALIGNED(va->va_start, align));

  	BUG_ON(va->va_start < vstart);
  	BUG_ON(va->va_end > vend);

  	ret = kasan_populate_vmalloc(addr, size);
  	if (ret) {
  		free_vmap_area(va);
  		return ERR_PTR(ret);
  	}

  	return va;

  
  overflow:

  	if (!purged) {
  		purge_vmap_area_lazy();
  		purged = 1;
  		goto retry;
  	}

  
  	if (gfpflags_allow_blocking(gfp_mask)) {
  		unsigned long freed = 0;
  		blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
  		if (freed > 0) {
  			purged = 0;
  			goto retry;
  		}
  	}

  	if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())

  		pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size
  ",
  			size);

  
  	kmem_cache_free(vmap_area_cachep, va);

  	return ERR_PTR(-EBUSY);

  }

  int register_vmap_purge_notifier(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_register(&vmap_notify_list, nb);
  }
  EXPORT_SYMBOL_GPL(register_vmap_purge_notifier);
  
  int unregister_vmap_purge_notifier(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_unregister(&vmap_notify_list, nb);
  }
  EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);

  /*

   * lazy_max_pages is the maximum amount of virtual address space we gather up
   * before attempting to purge with a TLB flush.
   *
   * There is a tradeoff here: a larger number will cover more kernel page tables
   * and take slightly longer to purge, but it will linearly reduce the number of
   * global TLB flushes that must be performed. It would seem natural to scale
   * this number up linearly with the number of CPUs (because vmapping activity
   * could also scale linearly with the number of CPUs), however it is likely
   * that in practice, workloads might be constrained in other ways that mean
   * vmap activity will not scale linearly with CPUs. Also, I want to be
   * conservative and not introduce a big latency on huge systems, so go with
   * a less aggressive log scale. It will still be an improvement over the old
   * code, and it will be simple to change the scale factor if we find that it
   * becomes a problem on bigger systems.
   */
  static unsigned long lazy_max_pages(void)
  {
  	unsigned int log;
  
  	log = fls(num_online_cpus());
  
  	return log * (32UL * 1024 * 1024 / PAGE_SIZE);
  }

  static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0);

  /*
   * Serialize vmap purging.  There is no actual criticial section protected
   * by this look, but we want to avoid concurrent calls for performance
   * reasons and to make the pcpu_get_vm_areas more deterministic.
   */

  static DEFINE_MUTEX(vmap_purge_lock);

  /* for per-CPU blocks */
  static void purge_fragmented_blocks_allcpus(void);

  /*

   * called before a call to iounmap() if the caller wants vm_area_struct's
   * immediately freed.
   */
  void set_iounmap_nonlazy(void)
  {

  	atomic_long_set(&vmap_lazy_nr, lazy_max_pages()+1);

  }
  
  /*

   * Purges all lazily-freed vmap areas.

   */

  static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)

  {

  	unsigned long resched_threshold;

  	struct llist_node *valist;

  	struct vmap_area *va;

  	struct vmap_area *n_va;

  	lockdep_assert_held(&vmap_purge_lock);

  	valist = llist_del_all(&vmap_purge_list);

  	if (unlikely(valist == NULL))
  		return false;
  
  	/*
  	 * TODO: to calculate a flush range without looping.
  	 * The list can be up to lazy_max_pages() elements.
  	 */

  	llist_for_each_entry(va, valist, purge_list) {

  		if (va->va_start < start)
  			start = va->va_start;
  		if (va->va_end > end)
  			end = va->va_end;

  	}

  	flush_tlb_kernel_range(start, end);

  	resched_threshold = lazy_max_pages() << 1;

  	spin_lock(&free_vmap_area_lock);

  	llist_for_each_entry_safe(va, n_va, valist, purge_list) {

  		unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT;

  		unsigned long orig_start = va->va_start;
  		unsigned long orig_end = va->va_end;

  		/*
  		 * Finally insert or merge lazily-freed area. It is
  		 * detached and there is no need to "unlink" it from
  		 * anything.
  		 */

  		va = merge_or_add_vmap_area(va, &free_vmap_area_root,
  					    &free_vmap_area_list);

  		if (!va)
  			continue;

  		if (is_vmalloc_or_module_addr((void *)orig_start))
  			kasan_release_vmalloc(orig_start, orig_end,
  					      va->va_start, va->va_end);

  		atomic_long_sub(nr, &vmap_lazy_nr);

  		if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)

  			cond_resched_lock(&free_vmap_area_lock);

  	}

  	spin_unlock(&free_vmap_area_lock);

  	return true;

  }
  
  /*

   * Kick off a purge of the outstanding lazy areas. Don't bother if somebody
   * is already purging.
   */
  static void try_purge_vmap_area_lazy(void)
  {

  	if (mutex_trylock(&vmap_purge_lock)) {

  		__purge_vmap_area_lazy(ULONG_MAX, 0);

  		mutex_unlock(&vmap_purge_lock);

  	}

  }
  
  /*

   * Kick off a purge of the outstanding lazy areas.
   */
  static void purge_vmap_area_lazy(void)
  {

  	mutex_lock(&vmap_purge_lock);

  	purge_fragmented_blocks_allcpus();
  	__purge_vmap_area_lazy(ULONG_MAX, 0);

  	mutex_unlock(&vmap_purge_lock);

  }
  
  /*

   * Free a vmap area, caller ensuring that the area has been unmapped
   * and flush_cache_vunmap had been called for the correct range
   * previously.

   */

  static void free_vmap_area_noflush(struct vmap_area *va)

  {

  	unsigned long nr_lazy;

  	spin_lock(&vmap_area_lock);
  	unlink_va(va, &vmap_area_root);
  	spin_unlock(&vmap_area_lock);

  	nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >>
  				PAGE_SHIFT, &vmap_lazy_nr);

  
  	/* After this point, we may free va at any time */
  	llist_add(&va->purge_list, &vmap_purge_list);
  
  	if (unlikely(nr_lazy > lazy_max_pages()))

  		try_purge_vmap_area_lazy();

  }

  /*
   * Free and unmap a vmap area
   */
  static void free_unmap_vmap_area(struct vmap_area *va)
  {
  	flush_cache_vunmap(va->va_start, va->va_end);

  	unmap_kernel_range_noflush(va->va_start, va->va_end - va->va_start);

  	if (debug_pagealloc_enabled_static())

  		flush_tlb_kernel_range(va->va_start, va->va_end);

  	free_vmap_area_noflush(va);

  }

  static struct vmap_area *find_vmap_area(unsigned long addr)
  {
  	struct vmap_area *va;
  
  	spin_lock(&vmap_area_lock);
  	va = __find_vmap_area(addr);
  	spin_unlock(&vmap_area_lock);
  
  	return va;
  }

  /*** Per cpu kva allocator ***/
  
  /*
   * vmap space is limited especially on 32 bit architectures. Ensure there is
   * room for at least 16 percpu vmap blocks per CPU.
   */
  /*
   * If we had a constant VMALLOC_START and VMALLOC_END, we'd like to be able
   * to #define VMALLOC_SPACE		(VMALLOC_END-VMALLOC_START). Guess
   * instead (we just need a rough idea)
   */
  #if BITS_PER_LONG == 32
  #define VMALLOC_SPACE		(128UL*1024*1024)
  #else
  #define VMALLOC_SPACE		(128UL*1024*1024*1024)
  #endif
  
  #define VMALLOC_PAGES		(VMALLOC_SPACE / PAGE_SIZE)
  #define VMAP_MAX_ALLOC		BITS_PER_LONG	/* 256K with 4K pages */
  #define VMAP_BBMAP_BITS_MAX	1024	/* 4MB with 4K pages */
  #define VMAP_BBMAP_BITS_MIN	(VMAP_MAX_ALLOC*2)
  #define VMAP_MIN(x, y)		((x) < (y) ? (x) : (y)) /* can't use min() */
  #define VMAP_MAX(x, y)		((x) > (y) ? (x) : (y)) /* can't use max() */

  #define VMAP_BBMAP_BITS		\
  		VMAP_MIN(VMAP_BBMAP_BITS_MAX,	\
  		VMAP_MAX(VMAP_BBMAP_BITS_MIN,	\
  			VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16))

  
  #define VMAP_BLOCK_SIZE		(VMAP_BBMAP_BITS * PAGE_SIZE)
  
  struct vmap_block_queue {
  	spinlock_t lock;
  	struct list_head free;

  };
  
  struct vmap_block {
  	spinlock_t lock;
  	struct vmap_area *va;

  	unsigned long free, dirty;

  	unsigned long dirty_min, dirty_max; /*< dirty range */

  	struct list_head free_list;
  	struct rcu_head rcu_head;

  	struct list_head purge;

  };
  
  /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */
  static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue);
  
  /*

   * XArray of vmap blocks, indexed by address, to quickly find a vmap block

   * in the free path. Could get rid of this if we change the API to return a
   * "cookie" from alloc, to be passed to free. But no big deal yet.
   */

  static DEFINE_XARRAY(vmap_blocks);

  
  /*
   * We should probably have a fallback mechanism to allocate virtual memory
   * out of partially filled vmap blocks. However vmap block sizing should be
   * fairly reasonable according to the vmalloc size, so it shouldn't be a
   * big problem.
   */
  
  static unsigned long addr_to_vb_idx(unsigned long addr)
  {
  	addr -= VMALLOC_START & ~(VMAP_BLOCK_SIZE-1);
  	addr /= VMAP_BLOCK_SIZE;
  	return addr;
  }

  static void *vmap_block_vaddr(unsigned long va_start, unsigned long pages_off)
  {
  	unsigned long addr;
  
  	addr = va_start + (pages_off << PAGE_SHIFT);
  	BUG_ON(addr_to_vb_idx(addr) != addr_to_vb_idx(va_start));
  	return (void *)addr;
  }
  
  /**
   * new_vmap_block - allocates new vmap_block and occupies 2^order pages in this
   *                  block. Of course pages number can't exceed VMAP_BBMAP_BITS
   * @order:    how many 2^order pages should be occupied in newly allocated block
   * @gfp_mask: flags for the page level allocator
   *

   * Return: virtual address in a newly allocated block or ERR_PTR(-errno)

   */
  static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)

  {
  	struct vmap_block_queue *vbq;
  	struct vmap_block *vb;
  	struct vmap_area *va;
  	unsigned long vb_idx;
  	int node, err;

  	void *vaddr;

  
  	node = numa_node_id();
  
  	vb = kmalloc_node(sizeof(struct vmap_block),
  			gfp_mask & GFP_RECLAIM_MASK, node);
  	if (unlikely(!vb))
  		return ERR_PTR(-ENOMEM);
  
  	va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
  					VMALLOC_START, VMALLOC_END,
  					node, gfp_mask);

  	if (IS_ERR(va)) {

  		kfree(vb);

  		return ERR_CAST(va);

  	}

  	vaddr = vmap_block_vaddr(va->va_start, 0);

  	spin_lock_init(&vb->lock);
  	vb->va = va;

  	/* At least something should be left free */
  	BUG_ON(VMAP_BBMAP_BITS <= (1UL << order));
  	vb->free = VMAP_BBMAP_BITS - (1UL << order);

  	vb->dirty = 0;

  	vb->dirty_min = VMAP_BBMAP_BITS;
  	vb->dirty_max = 0;

  	INIT_LIST_HEAD(&vb->free_list);

  
  	vb_idx = addr_to_vb_idx(va->va_start);

  	err = xa_insert(&vmap_blocks, vb_idx, vb, gfp_mask);
  	if (err) {
  		kfree(vb);
  		free_vmap_area(va);
  		return ERR_PTR(err);
  	}

  
  	vbq = &get_cpu_var(vmap_block_queue);

  	spin_lock(&vbq->lock);

  	list_add_tail_rcu(&vb->free_list, &vbq->free);

  	spin_unlock(&vbq->lock);

  	put_cpu_var(vmap_block_queue);

  	return vaddr;

  }

  static void free_vmap_block(struct vmap_block *vb)
  {
  	struct vmap_block *tmp;

  	tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start));

  	BUG_ON(tmp != vb);

  	free_vmap_area_noflush(vb->va);

  	kfree_rcu(vb, rcu_head);

  }

  static void purge_fragmented_blocks(int cpu)
  {
  	LIST_HEAD(purge);
  	struct vmap_block *vb;
  	struct vmap_block *n_vb;
  	struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(vb, &vbq->free, free_list) {
  
  		if (!(vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS))
  			continue;
  
  		spin_lock(&vb->lock);
  		if (vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS) {
  			vb->free = 0; /* prevent further allocs after releasing lock */
  			vb->dirty = VMAP_BBMAP_BITS; /* prevent purging it again */

  			vb->dirty_min = 0;
  			vb->dirty_max = VMAP_BBMAP_BITS;

  			spin_lock(&vbq->lock);
  			list_del_rcu(&vb->free_list);
  			spin_unlock(&vbq->lock);
  			spin_unlock(&vb->lock);
  			list_add_tail(&vb->purge, &purge);
  		} else
  			spin_unlock(&vb->lock);
  	}
  	rcu_read_unlock();
  
  	list_for_each_entry_safe(vb, n_vb, &purge, purge) {
  		list_del(&vb->purge);
  		free_vmap_block(vb);
  	}
  }

  static void purge_fragmented_blocks_allcpus(void)
  {
  	int cpu;
  
  	for_each_possible_cpu(cpu)
  		purge_fragmented_blocks(cpu);
  }

  static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
  {
  	struct vmap_block_queue *vbq;
  	struct vmap_block *vb;

  	void *vaddr = NULL;

  	unsigned int order;

  	BUG_ON(offset_in_page(size));

  	BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);

  	if (WARN_ON(size == 0)) {
  		/*
  		 * Allocating 0 bytes isn't what caller wants since
  		 * get_order(0) returns funny result. Just warn and terminate
  		 * early.
  		 */
  		return NULL;
  	}

  	order = get_order(size);

  	rcu_read_lock();
  	vbq = &get_cpu_var(vmap_block_queue);
  	list_for_each_entry_rcu(vb, &vbq->free, free_list) {

  		unsigned long pages_off;

  
  		spin_lock(&vb->lock);

  		if (vb->free < (1UL << order)) {
  			spin_unlock(&vb->lock);
  			continue;
  		}

  		pages_off = VMAP_BBMAP_BITS - vb->free;
  		vaddr = vmap_block_vaddr(vb->va->va_start, pages_off);

  		vb->free -= 1UL << order;
  		if (vb->free == 0) {
  			spin_lock(&vbq->lock);
  			list_del_rcu(&vb->free_list);
  			spin_unlock(&vbq->lock);
  		}

  		spin_unlock(&vb->lock);
  		break;

  	}

  	put_cpu_var(vmap_block_queue);

  	rcu_read_unlock();

  	/* Allocate new block if nothing was found */
  	if (!vaddr)
  		vaddr = new_vmap_block(order, gfp_mask);

  	return vaddr;

  }

  static void vb_free(unsigned long addr, unsigned long size)

  {
  	unsigned long offset;

  	unsigned int order;
  	struct vmap_block *vb;

  	BUG_ON(offset_in_page(size));

  	BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);

  	flush_cache_vunmap(addr, addr + size);

  	order = get_order(size);

  	offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;

  	vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr));

  	unmap_kernel_range_noflush(addr, size);

  	if (debug_pagealloc_enabled_static())

  		flush_tlb_kernel_range(addr, addr + size);

  	spin_lock(&vb->lock);

  
  	/* Expand dirty range */
  	vb->dirty_min = min(vb->dirty_min, offset);
  	vb->dirty_max = max(vb->dirty_max, offset + (1UL << order));

  	vb->dirty += 1UL << order;
  	if (vb->dirty == VMAP_BBMAP_BITS) {

  		BUG_ON(vb->free);

  		spin_unlock(&vb->lock);
  		free_vmap_block(vb);
  	} else
  		spin_unlock(&vb->lock);
  }

  static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)

  {

  	int cpu;

  	if (unlikely(!vmap_initialized))
  		return;

  	might_sleep();

  	for_each_possible_cpu(cpu) {
  		struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
  		struct vmap_block *vb;
  
  		rcu_read_lock();
  		list_for_each_entry_rcu(vb, &vbq->free, free_list) {

  			spin_lock(&vb->lock);

  			if (vb->dirty) {
  				unsigned long va_start = vb->va->va_start;

  				unsigned long s, e;

  				s = va_start + (vb->dirty_min << PAGE_SHIFT);
  				e = va_start + (vb->dirty_max << PAGE_SHIFT);

  				start = min(s, start);
  				end   = max(e, end);

  				flush = 1;

  			}
  			spin_unlock(&vb->lock);
  		}
  		rcu_read_unlock();
  	}

  	mutex_lock(&vmap_purge_lock);

  	purge_fragmented_blocks_allcpus();
  	if (!__purge_vmap_area_lazy(start, end) && flush)
  		flush_tlb_kernel_range(start, end);

  	mutex_unlock(&vmap_purge_lock);

  }

  
  /**
   * vm_unmap_aliases - unmap outstanding lazy aliases in the vmap layer
   *
   * The vmap/vmalloc layer lazily flushes kernel virtual mappings primarily
   * to amortize TLB flushing overheads. What this means is that any page you
   * have now, may, in a former life, have been mapped into kernel virtual
   * address by the vmap layer and so there might be some CPUs with TLB entries
   * still referencing that page (additional to the regular 1:1 kernel mapping).
   *
   * vm_unmap_aliases flushes all such lazy mappings. After it returns, we can
   * be sure that none of the pages we have control over will have any aliases
   * from the vmap layer.
   */
  void vm_unmap_aliases(void)
  {
  	unsigned long start = ULONG_MAX, end = 0;
  	int flush = 0;
  
  	_vm_unmap_aliases(start, end, flush);
  }

  EXPORT_SYMBOL_GPL(vm_unmap_aliases);
  
  /**
   * vm_unmap_ram - unmap linear kernel address space set up by vm_map_ram
   * @mem: the pointer returned by vm_map_ram
   * @count: the count passed to that vm_map_ram call (cannot unmap partial)
   */
  void vm_unmap_ram(const void *mem, unsigned int count)
  {

  	unsigned long size = (unsigned long)count << PAGE_SHIFT;

  	unsigned long addr = (unsigned long)mem;

  	struct vmap_area *va;

  	might_sleep();

  	BUG_ON(!addr);
  	BUG_ON(addr < VMALLOC_START);
  	BUG_ON(addr > VMALLOC_END);

  	BUG_ON(!PAGE_ALIGNED(addr));

  	kasan_poison_vmalloc(mem, size);

  	if (likely(count <= VMAP_MAX_ALLOC)) {

  		debug_check_no_locks_freed(mem, size);

  		vb_free(addr, size);

  		return;
  	}
  
  	va = find_vmap_area(addr);
  	BUG_ON(!va);

  	debug_check_no_locks_freed((void *)va->va_start,
  				    (va->va_end - va->va_start));

  	free_unmap_vmap_area(va);

  }
  EXPORT_SYMBOL(vm_unmap_ram);
  
  /**
   * vm_map_ram - map pages linearly into kernel virtual address (vmalloc space)
   * @pages: an array of pointers to the pages to be mapped
   * @count: number of pages
   * @node: prefer to allocate data structures on this node

   *

   * If you use this function for less than VMAP_MAX_ALLOC pages, it could be
   * faster than vmap so it's good.  But if you mix long-life and short-life
   * objects with vm_map_ram(), it could consume lots of address space through
   * fragmentation (especially on a 32bit machine).  You could see failures in
   * the end.  Please use this function for short-lived objects.
   *

   * Returns: a pointer to the address that has been mapped, or %NULL on failure

   */

  void *vm_map_ram(struct page **pages, unsigned int count, int node)

  {

  	unsigned long size = (unsigned long)count << PAGE_SHIFT;

  	unsigned long addr;
  	void *mem;
  
  	if (likely(count <= VMAP_MAX_ALLOC)) {
  		mem = vb_alloc(size, GFP_KERNEL);
  		if (IS_ERR(mem))
  			return NULL;
  		addr = (unsigned long)mem;
  	} else {
  		struct vmap_area *va;
  		va = alloc_vmap_area(size, PAGE_SIZE,
  				VMALLOC_START, VMALLOC_END, node, GFP_KERNEL);
  		if (IS_ERR(va))
  			return NULL;
  
  		addr = va->va_start;
  		mem = (void *)addr;
  	}

  
  	kasan_unpoison_vmalloc(mem, size);

  	if (map_kernel_range(addr, size, PAGE_KERNEL, pages) < 0) {

  		vm_unmap_ram(mem, count);
  		return NULL;
  	}
  	return mem;
  }
  EXPORT_SYMBOL(vm_map_ram);

  static struct vm_struct *vmlist __initdata;

  /**

   * vm_area_add_early - add vmap area early during boot
   * @vm: vm_struct to add
   *
   * This function is used to add fixed kernel vm area to vmlist before
   * vmalloc_init() is called.  @vm->addr, @vm->size, and @vm->flags
   * should contain proper values and the other fields should be zero.
   *
   * DO NOT USE THIS FUNCTION UNLESS YOU KNOW WHAT YOU'RE DOING.
   */
  void __init vm_area_add_early(struct vm_struct *vm)
  {
  	struct vm_struct *tmp, **p;
  
  	BUG_ON(vmap_initialized);
  	for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
  		if (tmp->addr >= vm->addr) {
  			BUG_ON(tmp->addr < vm->addr + vm->size);
  			break;
  		} else
  			BUG_ON(tmp->addr + tmp->size > vm->addr);
  	}
  	vm->next = *p;
  	*p = vm;
  }
  
  /**

   * vm_area_register_early - register vmap area early during boot
   * @vm: vm_struct to register

   * @align: requested alignment

   *
   * This function is used to register kernel vm area before
   * vmalloc_init() is called.  @vm->size and @vm->flags should contain
   * proper values on entry and other fields should be zero.  On return,
   * vm->addr contains the allocated address.
   *
   * DO NOT USE THIS FUNCTION UNLESS YOU KNOW WHAT YOU'RE DOING.
   */

  void __init vm_area_register_early(struct vm_struct *vm, size_t align)

  {
  	static size_t vm_init_off __initdata;

  	unsigned long addr;
  
  	addr = ALIGN(VMALLOC_START + vm_init_off, align);
  	vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;

  	vm->addr = (void *)addr;

  	vm_area_add_early(vm);

  }

  static void vmap_init_free_space(void)
  {
  	unsigned long vmap_start = 1;
  	const unsigned long vmap_end = ULONG_MAX;
  	struct vmap_area *busy, *free;
  
  	/*
  	 *     B     F     B     B     B     F
  	 * -|-----|.....|-----|-----|-----|.....|-
  	 *  |           The KVA space           |
  	 *  |<--------------------------------->|
  	 */
  	list_for_each_entry(busy, &vmap_area_list, list) {
  		if (busy->va_start - vmap_start > 0) {
  			free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
  			if (!WARN_ON_ONCE(!free)) {
  				free->va_start = vmap_start;
  				free->va_end = busy->va_start;
  
  				insert_vmap_area_augment(free, NULL,
  					&free_vmap_area_root,
  						&free_vmap_area_list);
  			}
  		}
  
  		vmap_start = busy->va_end;
  	}
  
  	if (vmap_end - vmap_start > 0) {
  		free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
  		if (!WARN_ON_ONCE(!free)) {
  			free->va_start = vmap_start;
  			free->va_end = vmap_end;
  
  			insert_vmap_area_augment(free, NULL,
  				&free_vmap_area_root,
  					&free_vmap_area_list);
  		}
  	}
  }

  void __init vmalloc_init(void)
  {

  	struct vmap_area *va;
  	struct vm_struct *tmp;

  	int i;

  	/*
  	 * Create the cache for vmap_area objects.
  	 */
  	vmap_area_cachep = KMEM_CACHE(vmap_area, SLAB_PANIC);

  	for_each_possible_cpu(i) {
  		struct vmap_block_queue *vbq;

  		struct vfree_deferred *p;

  
  		vbq = &per_cpu(vmap_block_queue, i);
  		spin_lock_init(&vbq->lock);
  		INIT_LIST_HEAD(&vbq->free);

  		p = &per_cpu(vfree_deferred, i);
  		init_llist_head(&p->list);
  		INIT_WORK(&p->wq, free_work);

  	}

  	/* Import existing vmlist entries. */
  	for (tmp = vmlist; tmp; tmp = tmp->next) {

  		va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
  		if (WARN_ON_ONCE(!va))
  			continue;

  		va->va_start = (unsigned long)tmp->addr;
  		va->va_end = va->va_start + tmp->size;

  		va->vm = tmp;

  		insert_vmap_area(va, &vmap_area_root, &vmap_area_list);

  	}

  	/*
  	 * Now we can initialize a free vmap space.
  	 */
  	vmap_init_free_space();

  	vmap_initialized = true;

  }

  /**

   * unmap_kernel_range - unmap kernel VM area and flush cache and TLB
   * @addr: start of the VM area to unmap
   * @size: size of the VM area to unmap
   *
   * Similar to unmap_kernel_range_noflush() but flushes vcache before
   * the unmapping and tlb after.
   */

  void unmap_kernel_range(unsigned long addr, unsigned long size)
  {
  	unsigned long end = addr + size;

  
  	flush_cache_vunmap(addr, end);

  	unmap_kernel_range_noflush(addr, size);

  	flush_tlb_kernel_range(addr, end);
  }

  static inline void setup_vmalloc_vm_locked(struct vm_struct *vm,
  	struct vmap_area *va, unsigned long flags, const void *caller)

  {

  	vm->flags = flags;
  	vm->addr = (void *)va->va_start;
  	vm->size = va->va_end - va->va_start;
  	vm->caller = caller;

  	va->vm = vm;

  }
  
  static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
  			      unsigned long flags, const void *caller)
  {
  	spin_lock(&vmap_area_lock);
  	setup_vmalloc_vm_locked(vm, va, flags, caller);

  	spin_unlock(&vmap_area_lock);

  }

  static void clear_vm_uninitialized_flag(struct vm_struct *vm)

  {

  	/*

  	 * Before removing VM_UNINITIALIZED,

  	 * we should make sure that vm has proper values.
  	 * Pair with smp_rmb() in show_numa_info().
  	 */
  	smp_wmb();

  	vm->flags &= ~VM_UNINITIALIZED;

  }

  static struct vm_struct *__get_vm_area_node(unsigned long size,

  		unsigned long align, unsigned long flags, unsigned long start,

  		unsigned long end, int node, gfp_t gfp_mask, const void *caller)

  {

  	struct vmap_area *va;

  	struct vm_struct *area;

  	unsigned long requested_size = size;

  	BUG_ON(in_interrupt());

  	size = PAGE_ALIGN(size);

  	if (unlikely(!size))
  		return NULL;

  	if (flags & VM_IOREMAP)
  		align = 1ul << clamp_t(int, get_count_order_long(size),
  				       PAGE_SHIFT, IOREMAP_MAX_ORDER);

  	area = kzalloc_node(sizeof(*area), gfp_mask & GFP_RECLAIM_MASK, node);

  	if (unlikely(!area))
  		return NULL;

  	if (!(flags & VM_NO_GUARD))
  		size += PAGE_SIZE;

  	va = alloc_vmap_area(size, align, start, end, node, gfp_mask);
  	if (IS_ERR(va)) {
  		kfree(area);
  		return NULL;

  	}

  	kasan_unpoison_vmalloc((void *)va->va_start, requested_size);

  	setup_vmalloc_vm(area, va, flags, caller);

  	return area;

  }

  struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
  				       unsigned long start, unsigned long end,

  				       const void *caller)

  {

  	return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE,
  				  GFP_KERNEL, caller);

  }