mm/vmalloc.c

/*
 *  linux/mm/vmalloc.c
 *
 *  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
 */

#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/sched.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/debugobjects.h>
#include <linux/kallsyms.h>
#include <linux/list.h>
#include <linux/notifier.h>
#include <linux/rbtree.h>
#include <linux/radix-tree.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/overflow.h>

#include <asm/uaccess.h>
#include <asm/tlbflush.h>
#include <asm/shmparam.h>

#include "internal.h"

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 *llnode = llist_del_all(&p->list);
	while (llnode) {
		void *p = llnode;
		llnode = llist_next(llnode);
		__vunmap(p, 1);
	}
}

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

static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
{
	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);
}

static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end)
{
	pmd_t *pmd;
	unsigned long next;

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_clear_huge(pmd))
			continue;
		if (pmd_none_or_clear_bad(pmd))
			continue;
		vunmap_pte_range(pmd, addr, next);
	} while (pmd++, addr = next, addr != end);
}

static void vunmap_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end)
{
	pud_t *pud;
	unsigned long next;

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_clear_huge(pud))
			continue;
		if (pud_none_or_clear_bad(pud))
			continue;
		vunmap_pmd_range(pud, addr, next);
	} while (pud++, addr = next, addr != end);
}

static void vunmap_page_range(unsigned long addr, unsigned long end)
{
	pgd_t *pgd;
	unsigned long next;

	BUG_ON(addr >= end);
	pgd = pgd_offset_k(addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
		vunmap_pud_range(pgd, addr, next);
	} while (pgd++, addr = next, addr != end);
}

static int vmap_pte_range(pmd_t *pmd, unsigned long addr,
		unsigned long end, pgprot_t prot, struct page **pages, int *nr)
{
	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(pmd, addr);
	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);
	return 0;
}

static int vmap_pmd_range(pud_t *pud, unsigned long addr,
		unsigned long end, pgprot_t prot, struct page **pages, int *nr)
{
	pmd_t *pmd;
	unsigned long next;

	pmd = pmd_alloc(&init_mm, pud, addr);
	if (!pmd)
		return -ENOMEM;
	do {
		next = pmd_addr_end(addr, end);
		if (vmap_pte_range(pmd, addr, next, prot, pages, nr))
			return -ENOMEM;
	} while (pmd++, addr = next, addr != end);
	return 0;
}

static int vmap_pud_range(pgd_t *pgd, unsigned long addr,
		unsigned long end, pgprot_t prot, struct page **pages, int *nr)
{
	pud_t *pud;
	unsigned long next;

	pud = pud_alloc(&init_mm, pgd, addr);
	if (!pud)
		return -ENOMEM;
	do {
		next = pud_addr_end(addr, end);
		if (vmap_pmd_range(pud, addr, next, prot, pages, nr))
			return -ENOMEM;
	} while (pud++, addr = next, addr != end);
	return 0;
}

/*
 * Set up page tables in kva (addr, end). The ptes shall have prot "prot", and
 * will have pfns corresponding to the "pages" array.
 *
 * Ie. pte at addr+N*PAGE_SIZE shall point to pfn corresponding to pages[N]
 */
static int vmap_page_range_noflush(unsigned long start, unsigned long end,
				   pgprot_t prot, struct page **pages)
{
	pgd_t *pgd;
	unsigned long next;
	unsigned long addr = start;
	int err = 0;
	int nr = 0;

	BUG_ON(addr >= end);
	pgd = pgd_offset_k(addr);
	do {
		next = pgd_addr_end(addr, end);
		err = vmap_pud_range(pgd, addr, next, prot, pages, &nr);
		if (err)
			return err;
	} while (pgd++, addr = next, addr != end);

	return nr;
}

static int vmap_page_range(unsigned long start, unsigned long end,
			   pgprot_t prot, struct page **pages)
{
	int ret;

	ret = vmap_page_range_noflush(start, end, prot, pages);
	flush_cache_vmap(start, end);
	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);

	/*
	 * 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));

	/*
	 * 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.
	 */
	if (!pgd_none(*pgd)) {
		pud_t *pud = pud_offset(pgd, addr);
		WARN_ON_ONCE(pud_bad(*pud));
		if (!pud_none(*pud) && !pud_bad(*pud)) {
			pmd_t *pmd = pmd_offset(pud, addr);
			WARN_ON_ONCE(pmd_bad(*pmd));
			if (!pmd_none(*pmd) && !pmd_bad(*pmd)) {
				pte_t *ptep, pte;

				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 VM_VM_AREA	0x04

static DEFINE_SPINLOCK(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;

/* The vmap cache globals are protected by vmap_area_lock */
static struct rb_node *free_vmap_cache;
static unsigned long cached_hole_size;
static unsigned long cached_vstart;
static unsigned long cached_align;

static unsigned long vmap_area_pcpu_hole;

#ifdef CONFIG_ENABLE_VMALLOC_SAVING
#define POSSIBLE_VMALLOC_START	PAGE_OFFSET

#define VMALLOC_BITMAP_SIZE	((VMALLOC_END - PAGE_OFFSET) >> \
					PAGE_SHIFT)
#define VMALLOC_TO_BIT(addr)	((addr - PAGE_OFFSET) >> PAGE_SHIFT)
#define BIT_TO_VMALLOC(i)	(PAGE_OFFSET + i * PAGE_SIZE)

unsigned long total_vmalloc_size;
unsigned long vmalloc_reserved;

DECLARE_BITMAP(possible_areas, VMALLOC_BITMAP_SIZE);

void mark_vmalloc_reserved_area(void *x, unsigned long size)
{
	unsigned long addr = (unsigned long)x;

	bitmap_set(possible_areas, VMALLOC_TO_BIT(addr), size >> PAGE_SHIFT);
	vmalloc_reserved += size;
}

int is_vmalloc_addr(const void *x)
{
	unsigned long addr = (unsigned long)x;

	if (addr < POSSIBLE_VMALLOC_START || addr >= VMALLOC_END)
		return 0;

	if (test_bit(VMALLOC_TO_BIT(addr), possible_areas))
		return 0;

	return 1;
}

static void calc_total_vmalloc_size(void)
{
	total_vmalloc_size = VMALLOC_END - POSSIBLE_VMALLOC_START -
		vmalloc_reserved;
}
#else
int is_vmalloc_addr(const void *x)
{
	unsigned long addr = (unsigned long)x;

	return addr >= VMALLOC_START && addr < VMALLOC_END;
}

static void calc_total_vmalloc_size(void) { }
#endif
EXPORT_SYMBOL(is_vmalloc_addr);

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;
}

static void __insert_vmap_area(struct vmap_area *va)
{
	struct rb_node **p = &vmap_area_root.rb_node;
	struct rb_node *parent = NULL;
	struct rb_node *tmp;

	while (*p) {
		struct vmap_area *tmp_va;

		parent = *p;
		tmp_va = rb_entry(parent, struct vmap_area, rb_node);
		if (va->va_start < tmp_va->va_end)
			p = &(*p)->rb_left;
		else if (va->va_end > tmp_va->va_start)
			p = &(*p)->rb_right;
		else
			BUG();
	}

	rb_link_node(&va->rb_node, parent, p);
	rb_insert_color(&va->rb_node, &vmap_area_root);

	/* address-sort this list */
	tmp = rb_prev(&va->rb_node);
	if (tmp) {
		struct vmap_area *prev;
		prev = rb_entry(tmp, struct vmap_area, rb_node);
		list_add_rcu(&va->list, &prev->list);
	} else
		list_add_rcu(&va->list, &vmap_area_list);
}

static void purge_vmap_area_lazy(void);

static BLOCKING_NOTIFIER_HEAD(vmap_notify_list);

/*
 * 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;
	struct rb_node *n;
	unsigned long addr;
	int purged = 0;
	struct vmap_area *first;

	BUG_ON(!size);
	BUG_ON(offset_in_page(size));
	BUG_ON(!is_power_of_2(align));

	might_sleep();

	va = kmalloc_node(sizeof(struct vmap_area),
			gfp_mask & GFP_RECLAIM_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 & GFP_RECLAIM_MASK);

retry:
	spin_lock(&vmap_area_lock);
	/*
	 * Invalidate cache if we have more permissive parameters.
	 * cached_hole_size notes the largest hole noticed _below_
	 * the vmap_area cached in free_vmap_cache: if size fits
	 * into that hole, we want to scan from vstart to reuse
	 * the hole instead of allocating above free_vmap_cache.
	 * Note that __free_vmap_area may update free_vmap_cache
	 * without updating cached_hole_size or cached_align.
	 */
	if (!free_vmap_cache ||
			size < cached_hole_size ||
			vstart < cached_vstart ||
			align < cached_align) {
nocache:
		cached_hole_size = 0;
		free_vmap_cache = NULL;
	}
	/* record if we encounter less permissive parameters */
	cached_vstart = vstart;
	cached_align = align;

	/* find starting point for our search */
	if (free_vmap_cache) {
		first = rb_entry(free_vmap_cache, struct vmap_area, rb_node);
		addr = ALIGN(first->va_end, align);
		if (addr < vstart)
			goto nocache;
		if (addr + size < addr)
			goto overflow;

	} else {
		addr = ALIGN(vstart, align);
		if (addr + size < addr)
			goto overflow;

		n = vmap_area_root.rb_node;
		first = NULL;

		while (n) {
			struct vmap_area *tmp;
			tmp = rb_entry(n, struct vmap_area, rb_node);
			if (tmp->va_end >= addr) {
				first = tmp;
				if (tmp->va_start <= addr)
					break;
				n = n->rb_left;
			} else
				n = n->rb_right;
		}

		if (!first)
			goto found;
	}

	/* from the starting point, walk areas until a suitable hole is found */
	while (addr + size > first->va_start && addr + size <= vend) {
		if (addr + cached_hole_size < first->va_start)
			cached_hole_size = first->va_start - addr;
		addr = ALIGN(first->va_end, align);
		if (addr + size < addr)
			goto overflow;

		if (list_is_last(&first->list, &vmap_area_list))
			goto found;

		first = list_next_entry(first, list);
	}

found:
	/*
	 * Check also calculated address against the vstart,
	 * because it can be 0 because of big align request.
	 */
	if (addr + size > vend || addr < vstart)
		goto overflow;

	va->va_start = addr;
	va->va_end = addr + size;
	va->flags = 0;
	__insert_vmap_area(va);
	free_vmap_cache = &va->rb_node;
	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);

	return va;

overflow:
	spin_unlock(&vmap_area_lock);
	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\n",
			size);
	kfree(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);

static void __free_vmap_area(struct vmap_area *va)
{
	BUG_ON(RB_EMPTY_NODE(&va->rb_node));

	if (free_vmap_cache) {
		if (va->va_end < cached_vstart) {
			free_vmap_cache = NULL;
		} else {
			struct vmap_area *cache;
			cache = rb_entry(free_vmap_cache, struct vmap_area, rb_node);
			if (va->va_start <= cache->va_start) {
				free_vmap_cache = rb_prev(&va->rb_node);
				/*
				 * We don't try to update cached_hole_size or
				 * cached_align, but it won't go very wrong.
				 */
			}
		}
	}
	rb_erase(&va->rb_node, &vmap_area_root);
	RB_CLEAR_NODE(&va->rb_node);
	list_del_rcu(&va->list);

	/*
	 * Track the highest possible candidate for pcpu area
	 * allocation.  Areas outside of vmalloc area can be returned
	 * here too, consider only end addresses which fall inside
	 * vmalloc area proper.
	 */
	if (va->va_end > VMALLOC_START && va->va_end <= VMALLOC_END)
		vmap_area_pcpu_hole = max(vmap_area_pcpu_hole, va->va_end);

	kfree_rcu(va, rcu_head);
}

/*
 * Free a region of KVA allocated by alloc_vmap_area
 */
static void free_vmap_area(struct vmap_area *va)
{
	spin_lock(&vmap_area_lock);
	__free_vmap_area(va);
	spin_unlock(&vmap_area_lock);
}

/*
 * Clear the pagetable entries of a given vmap_area
 */
static void unmap_vmap_area(struct vmap_area *va)
{
	vunmap_page_range(va->va_start, va->va_end);
}

static void vmap_debug_free_range(unsigned long start, unsigned long end)
{
	/*
	 * Unmap page tables and force a TLB flush immediately if pagealloc
	 * debugging is enabled.  This catches use after free bugs similarly to
	 * those in linear kernel virtual address space after a page has been
	 * freed.
	 *
	 * All the lazy freeing logic is still retained, in order to minimise
	 * intrusiveness of this debugging feature.
	 *
	 * This is going to be *slow* (linear kernel virtual address debugging
	 * doesn't do a broadcast TLB flush so it is a lot faster).
	 */
	if (debug_pagealloc_enabled()) {
		vunmap_page_range(start, end);
		flush_tlb_kernel_range(start, end);
	}
}

/*
 * 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 * (1UL * CONFIG_VMAP_LAZY_PURGING_FACTOR *
					1024 * 1024 / PAGE_SIZE);
}

static atomic_t vmap_lazy_nr = ATOMIC_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_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)
{
	struct llist_node *valist;
	struct vmap_area *va;
	struct vmap_area *n_va;
	bool do_free = false;

	lockdep_assert_held(&vmap_purge_lock);

	valist = llist_del_all(&vmap_purge_list);
	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;
		do_free = true;
	}

	if (!do_free)
		return false;

	flush_tlb_kernel_range(start, end);

	spin_lock(&vmap_area_lock);
	llist_for_each_entry_safe(va, n_va, valist, purge_list) {
		int nr = (va->va_end - va->va_start) >> PAGE_SHIFT;

		__free_vmap_area(va);
		atomic_sub(nr, &vmap_lazy_nr);
		cond_resched_lock(&vmap_area_lock);
	}
	spin_unlock(&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)
{
	int nr_lazy;

	nr_lazy = atomic_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_vmap_area(va);
	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)

static bool vmap_initialized __read_mostly = false;

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);

/*
 * Radix tree 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_SPINLOCK(vmap_block_tree_lock);
static RADIX_TREE(vmap_block_tree, GFP_ATOMIC);

/*
 * 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
 *
 * Returns: 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);
	}

	err = radix_tree_preload(gfp_mask);
	if (unlikely(err)) {
		kfree(vb);
		free_vmap_area(va);
		return ERR_PTR(err);
	}

	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);
	spin_lock(&vmap_block_tree_lock);
	err = radix_tree_insert(&vmap_block_tree, vb_idx, vb);
	spin_unlock(&vmap_block_tree_lock);
	BUG_ON(err);
	radix_tree_preload_end();

	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;
	unsigned long vb_idx;

	vb_idx = addr_to_vb_idx(vb->va->va_start);
	spin_lock(&vmap_block_tree_lock);
	tmp = radix_tree_delete(&vmap_block_tree, vb_idx);
	spin_unlock(&vmap_block_tree_lock);
	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(const void *addr, unsigned long size)
{
	unsigned long offset;
	unsigned long vb_idx;
	unsigned int order;
	struct vmap_block *vb;

	BUG_ON(offset_in_page(size));
	BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);

	flush_cache_vunmap((unsigned long)addr, (unsigned long)addr + size);

	order = get_order(size);

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

	vb_idx = addr_to_vb_idx((unsigned long)addr);
	rcu_read_lock();
	vb = radix_tree_lookup(&vmap_block_tree, vb_idx);
	rcu_read_unlock();
	BUG_ON(!vb);

	vunmap_page_range((unsigned long)addr, (unsigned long)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);
}

/**
 * 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 cpu;
	int flush = 0;

	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);
}
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));

	debug_check_no_locks_freed(mem, size);
	vmap_debug_free_range(addr, addr+size);

	if (likely(count <= VMAP_MAX_ALLOC)) {
		vb_free(mem, size);
		return;
	}

	va = find_vmap_area(addr);
	BUG_ON(!va);
	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
 * @prot: memory protection to use. PAGE_KERNEL for regular RAM
 *
 * 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, pgprot_t prot)
{
	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;
	}
	if (vmap_page_range(addr, addr + size, prot, pages) < 0) {
		vm_unmap_ram(mem, count);
		return NULL;
	}
	return mem;
}
EXPORT_SYMBOL(vm_map_ram);

static struct vm_struct *vmlist __initdata;

/**
 * vm_area_check_early - check if vmap area is already mapped
 * @vm: vm_struct to be checked
 *
 * This function is used to check if the vmap area has been
 * mapped already. @vm->addr, @vm->size and @vm->flags should
 * contain proper values.
 *
 */
int __init vm_area_check_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) {
			if (tmp->addr < vm->addr + vm->size)
				return 1;
		} else {
			if (tmp->addr + tmp->size > vm->addr)
				return 1;
		}
	}
	return 0;
}

/**
 * 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);
}

void __init vmalloc_init(void)
{
	struct vmap_area *va;
	struct vm_struct *tmp;
	int i;

	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 = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
		va->flags = VM_VM_AREA;
		va->va_start = (unsigned long)tmp->addr;
		va->va_end = va->va_start + tmp->size;
		va->vm = tmp;
		__insert_vmap_area(va);
	}

	vmap_area_pcpu_hole = VMALLOC_END;
	calc_total_vmalloc_size();
	vmap_initialized = true;
}

/**
 * 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:
 * The number of pages mapped on success, -errno on failure.
 */
int map_kernel_range_noflush(unsigned long addr, unsigned long size,
			     pgprot_t prot, struct page **pages)
{
	return vmap_page_range_noflush(addr, addr + size, prot, pages);
}

/**
 * unmap_kernel_range_noflush - unmap kernel VM area
 * @addr: 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 addr, unsigned long size)
{
	vunmap_page_range(addr, addr + size);
}
EXPORT_SYMBOL_GPL(unmap_kernel_range_noflush);

/**
 * 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);
	vunmap_page_range(addr, end);
	flush_tlb_kernel_range(addr, end);
}
EXPORT_SYMBOL_GPL(unmap_kernel_range);

int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page **pages)
{
	unsigned long addr = (unsigned long)area->addr;
	unsigned long end = addr + get_vm_area_size(area);
	int err;

	err = vmap_page_range(addr, end, prot, pages);

	return err > 0 ? 0 : err;
}
EXPORT_SYMBOL_GPL(map_vm_area);

static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
			      unsigned long flags, const void *caller)
{
	spin_lock(&vmap_area_lock);
	vm->flags = flags;
	vm->addr = (void *)va->va_start;
	vm->size = va->va_end - va->va_start;
	vm->caller = caller;
	va->vm = vm;
	va->flags |= VM_VM_AREA;
	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;

	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;
	}

	setup_vmalloc_vm(area, va, flags, caller);

	return area;
}

struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
				unsigned long start, unsigned long end)
{
	return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE,
				  GFP_KERNEL, __builtin_return_address(0));
}
EXPORT_SYMBOL_GPL(__get_vm_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);
}

/**
 *	get_vm_area  -  reserve a contiguous kernel virtual area
 *	@size:		size of the area
 *	@flags:		%VM_IOREMAP for I/O mappings or VM_ALLOC
 *
 *	Search an area of @size in the kernel virtual mapping area,
 *	and reserved it for out purposes.  Returns the area descriptor
 *	on success or %NULL on failure.
 */
struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
{
#ifdef CONFIG_ENABLE_VMALLOC_SAVING
	return __get_vm_area_node(size, 1, flags, PAGE_OFFSET, VMALLOC_END,
				  NUMA_NO_NODE, GFP_KERNEL,
				  __builtin_return_address(0));
#else
	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
				  NUMA_NO_NODE, GFP_KERNEL,
				  __builtin_return_address(0));
#endif
}

struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
				const void *caller)
{
#ifdef CONFIG_ENABLE_VMALLOC_SAVING
	return __get_vm_area_node(size, 1, flags, PAGE_OFFSET, VMALLOC_END,
				  NUMA_NO_NODE, GFP_KERNEL, caller);
#else
	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
				  NUMA_NO_NODE, GFP_KERNEL, caller);
#endif
}

/**
 *	find_vm_area  -  find a continuous kernel virtual area
 *	@addr:		base address
 *
 *	Search for the kernel VM area starting at @addr, and return it.
 *	It is up to the caller to do all required locking to keep the returned
 *	pointer valid.
 */
struct vm_struct *find_vm_area(const void *addr)
{
	struct vmap_area *va;

	va = find_vmap_area((unsigned long)addr);
	if (va && va->flags & VM_VM_AREA)
		return va->vm;

	return NULL;
}

/**
 *	remove_vm_area  -  find and remove a continuous kernel virtual area
 *	@addr:		base address
 *
 *	Search for the kernel VM area starting at @addr, and remove it.
 *	This function returns the found VM area, but using it is NOT safe
 *	on SMP machines, except for its size or flags.
 */
struct vm_struct *remove_vm_area(const void *addr)
{
	struct vmap_area *va;

	might_sleep();

	va = find_vmap_area((unsigned long)addr);
	if (va && va->flags & VM_VM_AREA) {
		struct vm_struct *vm = va->vm;

		spin_lock(&vmap_area_lock);
		va->vm = NULL;
		va->flags &= ~VM_VM_AREA;
		spin_unlock(&vmap_area_lock);

		vmap_debug_free_range(va->va_start, va->va_end);
		kasan_free_shadow(vm);
		free_unmap_vmap_area(va);

		return vm;
	}
	return NULL;
}

static void __vunmap(const void *addr, int deallocate_pages)
{
	struct vm_struct *area;

	if (!addr)
		return;

	if (WARN(!PAGE_ALIGNED(addr), "Trying to vfree() bad address (%p)\n",
			addr))
		return;

	area = find_vm_area(addr);
	if (unlikely(!area)) {
		WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
				addr);
		return;
	}

	debug_check_no_locks_freed(addr, get_vm_area_size(area));
	debug_check_no_obj_freed(addr, get_vm_area_size(area));

	remove_vm_area(addr);
	if (deallocate_pages) {
		int i;

		for (i = 0; i < area->nr_pages; i++) {
			struct page *page = area->pages[i];

			BUG_ON(!page);
			__free_pages(page, 0);
		}

		kvfree(area->pages);
	}

	kfree(area);
	return;
}

static inline void __vfree_deferred(const void *addr)
{
	/*
	 * Use raw_cpu_ptr() because this can be called from preemptible
	 * context. Preemption is absolutely fine here, because the llist_add()
	 * implementation is lockless, so it works even if we are adding to
	 * nother cpu's list.  schedule_work() should be fine with this too.
	 */
	struct vfree_deferred *p = raw_cpu_ptr(&vfree_deferred);

	if (llist_add((struct llist_node *)addr, &p->list))
		schedule_work(&p->wq);
}

/**
 *	vfree_atomic  -  release memory allocated by vmalloc()
 *	@addr:		memory base address
 *
 *	This one is just like vfree() but can be called in any atomic context
 *	except NMIs.
 */
void vfree_atomic(const void *addr)
{
	BUG_ON(in_nmi());

	kmemleak_free(addr);

	if (!addr)
		return;
	__vfree_deferred(addr);
}

/**
 *	vfree  -  release memory allocated by vmalloc()
 *	@addr:		memory base address
 *
 *	Free the virtually continuous memory area starting at @addr, as
 *	obtained from vmalloc(), vmalloc_32() or __vmalloc(). If @addr is
 *	NULL, no operation is performed.
 *
 *	Must not be called in NMI context (strictly speaking, only if we don't
 *	have CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG, but making the calling
 *	conventions for vfree() arch-depenedent would be a really bad idea)
 *
 *	NOTE: assumes that the object at *addr has a size >= sizeof(llist_node)
 */
void vfree(const void *addr)
{
	BUG_ON(in_nmi());

	kmemleak_free(addr);

	if (!addr)
		return;
	if (unlikely(in_interrupt()))
		__vfree_deferred(addr);
	else
		__vunmap(addr, 1);
}
EXPORT_SYMBOL(vfree);

/**
 *	vunmap  -  release virtual mapping obtained by vmap()
 *	@addr:		memory base address
 *
 *	Free the virtually contiguous memory area starting at @addr,
 *	which was created from the page array passed to vmap().
 *
 *	Must not be called in interrupt context.
 */
void vunmap(const void *addr)
{
	BUG_ON(in_interrupt());
	might_sleep();
	if (addr)
		__vunmap(addr, 0);
}
EXPORT_SYMBOL(vunmap);

/**
 *	vmap  -  map an array of pages into virtually contiguous space
 *	@pages:		array of page pointers
 *	@count:		number of pages to map
 *	@flags:		vm_area->flags
 *	@prot:		page protection for the mapping
 *
 *	Maps @count pages from @pages into contiguous kernel virtual
 *	space.
 */
void *vmap(struct page **pages, unsigned int count,
		unsigned long flags, pgprot_t prot)
{
	struct vm_struct *area;
	unsigned long size;		/* In bytes */

	might_sleep();

	if (count > totalram_pages)
		return NULL;

	size = (unsigned long)count << PAGE_SHIFT;
	area = get_vm_area_caller(size, flags, __builtin_return_address(0));
	if (!area)
		return NULL;

	if (map_vm_area(area, prot, pages)) {
		vunmap(area->addr);
		return NULL;
	}

	return area->addr;
}
EXPORT_SYMBOL(vmap);

static void *__vmalloc_node(unsigned long size, unsigned long align,
			    gfp_t gfp_mask, pgprot_t prot,
			    int node, const void *caller);
static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
				 pgprot_t prot, int node)
{
	struct page **pages;
	unsigned int nr_pages, array_size, i;
	const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
	const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;

	nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
	array_size = (nr_pages * sizeof(struct page *));

	area->nr_pages = nr_pages;
	/* Please note that the recursion is strictly bounded. */
	if (array_size > PAGE_SIZE) {
		pages = __vmalloc_node(array_size, 1, nested_gfp|__GFP_HIGHMEM,
				PAGE_KERNEL, node, area->caller);
	} else {
		pages = kmalloc_node(array_size, nested_gfp, node);
	}
	area->pages = pages;
	if (!area->pages) {
		remove_vm_area(area->addr);
		kfree(area);
		return NULL;
	}

	for (i = 0; i < area->nr_pages; i++) {
		struct page *page;

		if (node == NUMA_NO_NODE)
			page = alloc_page(alloc_mask);
		else
			page = alloc_pages_node(node, alloc_mask, 0);

		if (unlikely(!page)) {
			/* Successfully allocated i pages, free them in __vunmap() */
			area->nr_pages = i;
			goto fail;
		}
		area->pages[i] = page;
		if (gfpflags_allow_blocking(gfp_mask))
			cond_resched();
	}

	if (map_vm_area(area, prot, pages))
		goto fail;
	return area->addr;

fail:
	warn_alloc(gfp_mask,
			  "vmalloc: allocation failure, allocated %ld of %ld bytes",
			  (area->nr_pages*PAGE_SIZE), area->size);
	vfree(area->addr);
	return NULL;
}

/**
 *	__vmalloc_node_range  -  allocate virtually contiguous memory
 *	@size:		allocation size
 *	@align:		desired alignment
 *	@start:		vm area range start
 *	@end:		vm area range end
 *	@gfp_mask:	flags for the page level allocator
 *	@prot:		protection mask for the allocated pages
 *	@vm_flags:	additional vm area flags (e.g. %VM_NO_GUARD)
 *	@node:		node to use for allocation or NUMA_NO_NODE
 *	@caller:	caller's return address
 *
 *	Allocate enough pages to cover @size from the page level
 *	allocator with @gfp_mask flags.  Map them into contiguous
 *	kernel virtual space, using a pagetable protection of @prot.
 */
void *__vmalloc_node_range(unsigned long size, unsigned long align,
			unsigned long start, unsigned long end, gfp_t gfp_mask,
			pgprot_t prot, unsigned long vm_flags, int node,
			const void *caller)
{
	struct vm_struct *area;
	void *addr;
	unsigned long real_size = size;

	size = PAGE_ALIGN(size);
	if (!size || (size >> PAGE_SHIFT) > totalram_pages)
		goto fail;

	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
				vm_flags, start, end, node, gfp_mask, caller);
	if (!area)
		goto fail;

	addr = __vmalloc_area_node(area, gfp_mask, prot, node);
	if (!addr)
		return NULL;

	/*
	 * First make sure the mappings are removed from all page-tables
	 * before they are freed.
	 */
	vmalloc_sync_unmappings();

	/*
	 * In this function, newly allocated vm_struct has VM_UNINITIALIZED
	 * flag. It means that vm_struct is not fully initialized.
	 * Now, it is fully initialized, so remove this flag here.
	 */
	clear_vm_uninitialized_flag(area);

	/*
	 * A ref_count = 2 is needed because vm_struct allocated in
	 * __get_vm_area_node() contains a reference to the virtual address of
	 * the vmalloc'ed block.
	 */
	kmemleak_alloc(addr, real_size, 2, gfp_mask);

	return addr;

fail:
	warn_alloc(gfp_mask,
			  "vmalloc: allocation failure: %lu bytes", real_size);
	return NULL;
}

/**
 *	__vmalloc_node  -  allocate virtually contiguous memory
 *	@size:		allocation size
 *	@align:		desired alignment
 *	@gfp_mask:	flags for the page level allocator
 *	@prot:		protection mask for the allocated pages
 *	@node:		node to use for allocation or NUMA_NO_NODE
 *	@caller:	caller's return address
 *
 *	Allocate enough pages to cover @size from the page level
 *	allocator with @gfp_mask flags.  Map them into contiguous
 *	kernel virtual space, using a pagetable protection of @prot.
 */
static void *__vmalloc_node(unsigned long size, unsigned long align,
			    gfp_t gfp_mask, pgprot_t prot,
			    int node, const void *caller)
{
	return __vmalloc_node_range(size, align, VMALLOC_START, VMALLOC_END,
				gfp_mask, prot, 0, node, caller);
}

void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
{
	return __vmalloc_node(size, 1, gfp_mask, prot, NUMA_NO_NODE,
				__builtin_return_address(0));
}
EXPORT_SYMBOL(__vmalloc);

static inline void *__vmalloc_node_flags(unsigned long size,
					int node, gfp_t flags)
{
	return __vmalloc_node(size, 1, flags, PAGE_KERNEL,
					node, __builtin_return_address(0));
}

/**
 *	vmalloc  -  allocate virtually contiguous memory
 *	@size:		allocation size
 *	Allocate enough pages to cover @size from the page level
 *	allocator and map them into contiguous kernel virtual space.
 *
 *	For tight control over page level allocator and protection flags
 *	use __vmalloc() instead.
 */
void *vmalloc(unsigned long size)
{
	return __vmalloc_node_flags(size, NUMA_NO_NODE,
				    GFP_KERNEL | __GFP_HIGHMEM);
}
EXPORT_SYMBOL(vmalloc);

/**
 *	vzalloc - allocate virtually contiguous memory with zero fill
 *	@size:	allocation size
 *	Allocate enough pages to cover @size from the page level
 *	allocator and map them into contiguous kernel virtual space.
 *	The memory allocated is set to zero.
 *
 *	For tight control over page level allocator and protection flags
 *	use __vmalloc() instead.
 */
void *vzalloc(unsigned long size)
{
	return __vmalloc_node_flags(size, NUMA_NO_NODE,
				GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
}
EXPORT_SYMBOL(vzalloc);

/**
 * vmalloc_user - allocate zeroed virtually contiguous memory for userspace
 * @size: allocation size
 *
 * The resulting memory area is zeroed so it can be mapped to userspace
 * without leaking data.
 */
void *vmalloc_user(unsigned long size)
{
	struct vm_struct *area;
	void *ret;

	ret = __vmalloc_node(size, SHMLBA,
			     GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
			     PAGE_KERNEL, NUMA_NO_NODE,
			     __builtin_return_address(0));
	if (ret) {
		area = find_vm_area(ret);
		area->flags |= VM_USERMAP;
	}
	return ret;
}
EXPORT_SYMBOL(vmalloc_user);

/**
 *	vmalloc_node  -  allocate memory on a specific node
 *	@size:		allocation size
 *	@node:		numa node
 *
 *	Allocate enough pages to cover @size from the page level
 *	allocator and map them into contiguous kernel virtual space.
 *
 *	For tight control over page level allocator and protection flags
 *	use __vmalloc() instead.
 */
void *vmalloc_node(unsigned long size, int node)
{
	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
					node, __builtin_return_address(0));
}
EXPORT_SYMBOL(vmalloc_node);

/**
 * vzalloc_node - allocate memory on a specific node with zero fill
 * @size:	allocation size
 * @node:	numa node
 *
 * Allocate enough pages to cover @size from the page level
 * allocator and map them into contiguous kernel virtual space.
 * The memory allocated is set to zero.
 *
 * For tight control over page level allocator and protection flags
 * use __vmalloc_node() instead.
 */
void *vzalloc_node(unsigned long size, int node)
{
	return __vmalloc_node_flags(size, node,
			 GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
}
EXPORT_SYMBOL(vzalloc_node);

#ifndef PAGE_KERNEL_EXEC
# define PAGE_KERNEL_EXEC PAGE_KERNEL
#endif

/**
 *	vmalloc_exec  -  allocate virtually contiguous, executable memory
 *	@size:		allocation size
 *
 *	Kernel-internal function to allocate enough pages to cover @size
 *	the page level allocator and map them into contiguous and
 *	executable kernel virtual space.
 *
 *	For tight control over page level allocator and protection flags
 *	use __vmalloc() instead.
 */

void *vmalloc_exec(unsigned long size)
{
	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
			      NUMA_NO_NODE, __builtin_return_address(0));
}

#if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
#elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
#define GFP_VMALLOC32 GFP_DMA | GFP_KERNEL
#else
#define GFP_VMALLOC32 GFP_KERNEL
#endif

/**
 *	vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
 *	@size:		allocation size
 *
 *	Allocate enough 32bit PA addressable pages to cover @size from the
 *	page level allocator and map them into contiguous kernel virtual space.
 */
void *vmalloc_32(unsigned long size)
{
	return __vmalloc_node(size, 1, GFP_VMALLOC32, PAGE_KERNEL,
			      NUMA_NO_NODE, __builtin_return_address(0));
}
EXPORT_SYMBOL(vmalloc_32);

/**
 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
 *	@size:		allocation size
 *
 * The resulting memory area is 32bit addressable and zeroed so it can be
 * mapped to userspace without leaking data.
 */
void *vmalloc_32_user(unsigned long size)
{
	struct vm_struct *area;
	void *ret;

	ret = __vmalloc_node(size, 1, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
			     NUMA_NO_NODE, __builtin_return_address(0));
	if (ret) {
		area = find_vm_area(ret);
		area->flags |= VM_USERMAP;
	}
	return ret;
}
EXPORT_SYMBOL(vmalloc_32_user);

/*
 * small helper routine , copy contents to buf from addr.
 * If the page is not present, fill zero.
 */

static int aligned_vread(char *buf, char *addr, unsigned long count)
{
	struct page *p;
	int copied = 0;

	while (count) {
		unsigned long offset, length;

		offset = offset_in_page(addr);
		length = PAGE_SIZE - offset;
		if (length > count)
			length = count;
		p = vmalloc_to_page(addr);
		/*
		 * To do safe access to this _mapped_ area, we need
		 * lock. But adding lock here means that we need to add
		 * overhead of vmalloc()/vfree() calles for this _debug_
		 * interface, rarely used. Instead of that, we'll use
		 * kmap() and get small overhead in this access function.
		 */
		if (p) {
			/*
			 * we can expect USER0 is not used (see vread/vwrite's
			 * function description)
			 */
			void *map = kmap_atomic(p);
			memcpy(buf, map + offset, length);
			kunmap_atomic(map);
		} else
			memset(buf, 0, length);

		addr += length;
		buf += length;
		copied += length;
		count -= length;
	}
	return copied;
}

static int aligned_vwrite(char *buf, char *addr, unsigned long count)
{
	struct page *p;
	int copied = 0;

	while (count) {
		unsigned long offset, length;

		offset = offset_in_page(addr);
		length = PAGE_SIZE - offset;
		if (length > count)
			length = count;
		p = vmalloc_to_page(addr);
		/*
		 * To do safe access to this _mapped_ area, we need
		 * lock. But adding lock here means that we need to add
		 * overhead of vmalloc()/vfree() calles for this _debug_
		 * interface, rarely used. Instead of that, we'll use
		 * kmap() and get small overhead in this access function.
		 */
		if (p) {
			/*
			 * we can expect USER0 is not used (see vread/vwrite's
			 * function description)
			 */
			void *map = kmap_atomic(p);
			memcpy(map + offset, buf, length);
			kunmap_atomic(map);
		}
		addr += length;
		buf += length;
		copied += length;
		count -= length;
	}
	return copied;
}

/**
 *	vread() -  read vmalloc area in a safe way.
 *	@buf:		buffer for reading data
 *	@addr:		vm address.
 *	@count:		number of bytes to be read.
 *
 *	Returns # of bytes which addr and buf should be increased.
 *	(same number to @count). Returns 0 if [addr...addr+count) doesn't
 *	includes any intersect with alive vmalloc area.
 *
 *	This function checks that addr is a valid vmalloc'ed area, and
 *	copy data from that area to a given buffer. If the given memory range
 *	of [addr...addr+count) includes some valid address, data is copied to
 *	proper area of @buf. If there are memory holes, they'll be zero-filled.
 *	IOREMAP area is treated as memory hole and no copy is done.
 *
 *	If [addr...addr+count) doesn't includes any intersects with alive
 *	vm_struct area, returns 0. @buf should be kernel's buffer.
 *
 *	Note: In usual ops, vread() is never necessary because the caller
 *	should know vmalloc() area is valid and can use memcpy().
 *	This is for routines which have to access vmalloc area without
 *	any informaion, as /dev/kmem.
 *
 */

long vread(char *buf, char *addr, unsigned long count)
{
	struct vmap_area *va;
	struct vm_struct *vm;
	char *vaddr, *buf_start = buf;
	unsigned long buflen = count;
	unsigned long n;

	/* Don't allow overflow */
	if ((unsigned long) addr + count < count)
		count = -(unsigned long) addr;

	spin_lock(&vmap_area_lock);
	list_for_each_entry(va, &vmap_area_list, list) {
		if (!count)
			break;

		if (!(va->flags & VM_VM_AREA))
			continue;

		vm = va->vm;
		vaddr = (char *) vm->addr;
		if (addr >= vaddr + get_vm_area_size(vm))
			continue;
		while (addr < vaddr) {
			if (count == 0)
				goto finished;
			*buf = '\0';
			buf++;
			addr++;
			count--;
		}
		n = vaddr + get_vm_area_size(vm) - addr;
		if (n > count)
			n = count;
		if (!(vm->flags & VM_IOREMAP))
			aligned_vread(buf, addr, n);
		else /* IOREMAP area is treated as memory hole */
			memset(buf, 0, n);
		buf += n;
		addr += n;
		count -= n;
	}
finished:
	spin_unlock(&vmap_area_lock);

	if (buf == buf_start)
		return 0;
	/* zero-fill memory holes */
	if (buf != buf_start + buflen)
		memset(buf, 0, buflen - (buf - buf_start));

	return buflen;
}

/**
 *	vwrite() -  write vmalloc area in a safe way.
 *	@buf:		buffer for source data
 *	@addr:		vm address.
 *	@count:		number of bytes to be read.
 *
 *	Returns # of bytes which addr and buf should be incresed.
 *	(same number to @count).
 *	If [addr...addr+count) doesn't includes any intersect with valid
 *	vmalloc area, returns 0.
 *
 *	This function checks that addr is a valid vmalloc'ed area, and
 *	copy data from a buffer to the given addr. If specified range of
 *	[addr...addr+count) includes some valid address, data is copied from
 *	proper area of @buf. If there are memory holes, no copy to hole.
 *	IOREMAP area is treated as memory hole and no copy is done.
 *
 *	If [addr...addr+count) doesn't includes any intersects with alive
 *	vm_struct area, returns 0. @buf should be kernel's buffer.
 *
 *	Note: In usual ops, vwrite() is never necessary because the caller
 *	should know vmalloc() area is valid and can use memcpy().
 *	This is for routines which have to access vmalloc area without
 *	any informaion, as /dev/kmem.
 */

long vwrite(char *buf, char *addr, unsigned long count)
{
	struct vmap_area *va;
	struct vm_struct *vm;
	char *vaddr;
	unsigned long n, buflen;
	int copied = 0;

	/* Don't allow overflow */
	if ((unsigned long) addr + count < count)
		count = -(unsigned long) addr;
	buflen = count;

	spin_lock(&vmap_area_lock);
	list_for_each_entry(va, &vmap_area_list, list) {
		if (!count)
			break;

		if (!(va->flags & VM_VM_AREA))
			continue;

		vm = va->vm;
		vaddr = (char *) vm->addr;
		if (addr >= vaddr + get_vm_area_size(vm))
			continue;
		while (addr < vaddr) {
			if (count == 0)
				goto finished;
			buf++;
			addr++;
			count--;
		}
		n = vaddr + get_vm_area_size(vm) - addr;
		if (n > count)
			n = count;
		if (!(vm->flags & VM_IOREMAP)) {
			aligned_vwrite(buf, addr, n);
			copied++;
		}
		buf += n;
		addr += n;
		count -= n;
	}
finished:
	spin_unlock(&vmap_area_lock);
	if (!copied)
		return 0;
	return buflen;
}

/**
 *	remap_vmalloc_range_partial  -  map vmalloc pages to userspace
 *	@vma:		vma to cover
 *	@uaddr:		target user address to start at
 *	@kaddr:		virtual address of vmalloc kernel memory
 *	@pgoff:		offset from @kaddr to start at
 *	@size:		size of map area
 *
 *	Returns:	0 for success, -Exxx on failure
 *
 *	This function checks that @kaddr is a valid vmalloc'ed area,
 *	and that it is big enough to cover the range starting at
 *	@uaddr in @vma. Will return failure if that criteria isn't
 *	met.
 *
 *	Similar to remap_pfn_range() (see mm/memory.c)
 */
int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
				void *kaddr, unsigned long pgoff,
				unsigned long size)
{
	struct vm_struct *area;
	unsigned long off;
	unsigned long end_index;

	if (check_shl_overflow(pgoff, PAGE_SHIFT, &off))
		return -EINVAL;

	size = PAGE_ALIGN(size);

	if (!PAGE_ALIGNED(uaddr) || !PAGE_ALIGNED(kaddr))
		return -EINVAL;

	area = find_vm_area(kaddr);
	if (!area)
		return -EINVAL;

	if (!(area->flags & VM_USERMAP))
		return -EINVAL;

	if (check_add_overflow(size, off, &end_index) ||
	    end_index > get_vm_area_size(area))
		return -EINVAL;
	kaddr += off;

	do {
		struct page *page = vmalloc_to_page(kaddr);
		int ret;

		ret = vm_insert_page(vma, uaddr, page);
		if (ret)
			return ret;

		uaddr += PAGE_SIZE;
		kaddr += PAGE_SIZE;
		size -= PAGE_SIZE;
	} while (size > 0);

	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;

	return 0;
}
EXPORT_SYMBOL(remap_vmalloc_range_partial);

/**
 *	remap_vmalloc_range  -  map vmalloc pages to userspace
 *	@vma:		vma to cover (map full range of vma)
 *	@addr:		vmalloc memory
 *	@pgoff:		number of pages into addr before first page to map
 *
 *	Returns:	0 for success, -Exxx on failure
 *
 *	This function checks that addr is a valid vmalloc'ed area, and
 *	that it is big enough to cover the vma. Will return failure if
 *	that criteria isn't met.
 *
 *	Similar to remap_pfn_range() (see mm/memory.c)
 */
int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
						unsigned long pgoff)
{
	return remap_vmalloc_range_partial(vma, vma->vm_start,
					   addr, pgoff,
					   vma->vm_end - vma->vm_start);
}
EXPORT_SYMBOL(remap_vmalloc_range);

/*
 * Implement stubs for vmalloc_sync_[un]mappings () if the architecture chose
 * not to have one.
 *
 * The purpose of this function is to make sure the vmalloc area
 * mappings are identical in all page-tables in the system.
 */
void __weak vmalloc_sync_mappings(void)
{
}

void __weak vmalloc_sync_unmappings(void)
{
}

static int f(pte_t *pte, pgtable_t table, unsigned long addr, void *data)
{
	pte_t ***p = data;

	if (p) {
		*(*p) = pte;
		(*p)++;
	}
	return 0;
}

/**
 *	alloc_vm_area - allocate a range of kernel address space
 *	@size:		size of the area
 *	@ptes:		returns the PTEs for the address space
 *
 *	Returns:	NULL on failure, vm_struct on success
 *
 *	This function reserves a range of kernel address space, and
 *	allocates pagetables to map that range.  No actual mappings
 *	are created.
 *
 *	If @ptes is non-NULL, pointers to the PTEs (in init_mm)
 *	allocated for the VM area are returned.
 */
struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
{
	struct vm_struct *area;

	area = get_vm_area_caller(size, VM_IOREMAP,
				__builtin_return_address(0));
	if (area == NULL)
		return NULL;

	/*
	 * This ensures that page tables are constructed for this region
	 * of kernel virtual address space and mapped into init_mm.
	 */
	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
				size, f, ptes ? &ptes : NULL)) {
		free_vm_area(area);
		return NULL;
	}

	return area;
}
EXPORT_SYMBOL_GPL(alloc_vm_area);

void free_vm_area(struct vm_struct *area)
{
	struct vm_struct *ret;
	ret = remove_vm_area(area->addr);
	BUG_ON(ret != area);
	kfree(area);
}
EXPORT_SYMBOL_GPL(free_vm_area);

#ifdef CONFIG_SMP
static struct vmap_area *node_to_va(struct rb_node *n)
{
	return n ? rb_entry(n, struct vmap_area, rb_node) : NULL;
}

/**
 * pvm_find_next_prev - find the next and prev vmap_area surrounding @end
 * @end: target address
 * @pnext: out arg for the next vmap_area
 * @pprev: out arg for the previous vmap_area
 *
 * Returns: %true if either or both of next and prev are found,
 *	    %false if no vmap_area exists
 *
 * Find vmap_areas end addresses of which enclose @end.  ie. if not
 * NULL, *pnext->va_end > @end and *pprev->va_end <= @end.
 */
static bool pvm_find_next_prev(unsigned long end,
			       struct vmap_area **pnext,
			       struct vmap_area **pprev)
{
	struct rb_node *n = vmap_area_root.rb_node;
	struct vmap_area *va = NULL;

	while (n) {
		va = rb_entry(n, struct vmap_area, rb_node);
		if (end < va->va_end)
			n = n->rb_left;
		else if (end > va->va_end)
			n = n->rb_right;
		else
			break;
	}

	if (!va)
		return false;

	if (va->va_end > end) {
		*pnext = va;
		*pprev = node_to_va(rb_prev(&(*pnext)->rb_node));
	} else {
		*pprev = va;
		*pnext = node_to_va(rb_next(&(*pprev)->rb_node));
	}
	return true;
}

/**
 * pvm_determine_end - find the highest aligned address between two vmap_areas
 * @pnext: in/out arg for the next vmap_area
 * @pprev: in/out arg for the previous vmap_area
 * @align: alignment
 *
 * Returns: determined end address
 *
 * Find the highest aligned address between *@pnext and *@pprev below
 * VMALLOC_END.  *@pnext and *@pprev are adjusted so that the aligned
 * down address is between the end addresses of the two vmap_areas.
 *
 * Please note that the address returned by this function may fall
 * inside *@pnext vmap_area.  The caller is responsible for checking
 * that.
 */
static unsigned long pvm_determine_end(struct vmap_area **pnext,
				       struct vmap_area **pprev,
				       unsigned long align)
{
	const unsigned long vmalloc_end = VMALLOC_END & ~(align - 1);
	unsigned long addr;

	if (*pnext)
		addr = min((*pnext)->va_start & ~(align - 1), vmalloc_end);
	else
		addr = vmalloc_end;

	while (*pprev && (*pprev)->va_end > addr) {
		*pnext = *pprev;
		*pprev = node_to_va(rb_prev(&(*pnext)->rb_node));
	}

	return addr;
}

/**
 * pcpu_get_vm_areas - allocate vmalloc areas for percpu allocator
 * @offsets: array containing offset of each area
 * @sizes: array containing size of each area
 * @nr_vms: the number of areas to allocate
 * @align: alignment, all entries in @offsets and @sizes must be aligned to this
 *
 * Returns: kmalloc'd vm_struct pointer array pointing to allocated
 *	    vm_structs on success, %NULL on failure
 *
 * Percpu allocator wants to use congruent vm areas so that it can
 * maintain the offsets among percpu areas.  This function allocates
 * congruent vmalloc areas for it with GFP_KERNEL.  These areas tend to
 * be scattered pretty far, distance between two areas easily going up
 * to gigabytes.  To avoid interacting with regular vmallocs, these
 * areas are allocated from top.
 *
 * Despite its complicated look, this allocator is rather simple.  It
 * does everything top-down and scans areas from the end looking for
 * matching slot.  While scanning, if any of the areas overlaps with
 * existing vmap_area, the base address is pulled down to fit the
 * area.  Scanning is repeated till all the areas fit and then all
 * necessary data structres are inserted and the result is returned.
 */
struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
				     const size_t *sizes, int nr_vms,
				     size_t align)
{
	const unsigned long vmalloc_start = ALIGN(VMALLOC_START, align);
	const unsigned long vmalloc_end = VMALLOC_END & ~(align - 1);
	struct vmap_area **vas, *prev, *next;
	struct vm_struct **vms;
	int area, area2, last_area, term_area;
	unsigned long base, start, end, last_end;
	bool purged = false;

	/* verify parameters and allocate data structures */
	BUG_ON(offset_in_page(align) || !is_power_of_2(align));
	for (last_area = 0, area = 0; area < nr_vms; area++) {
		start = offsets[area];
		end = start + sizes[area];

		/* is everything aligned properly? */
		BUG_ON(!IS_ALIGNED(offsets[area], align));
		BUG_ON(!IS_ALIGNED(sizes[area], align));

		/* detect the area with the highest address */
		if (start > offsets[last_area])
			last_area = area;

		for (area2 = 0; area2 < nr_vms; area2++) {
			unsigned long start2 = offsets[area2];
			unsigned long end2 = start2 + sizes[area2];

			if (area2 == area)
				continue;

			BUG_ON(start2 >= start && start2 < end);
			BUG_ON(end2 <= end && end2 > start);
		}
	}
	last_end = offsets[last_area] + sizes[last_area];

	if (vmalloc_end - vmalloc_start < last_end) {
		WARN_ON(true);
		return NULL;
	}

	vms = kcalloc(nr_vms, sizeof(vms[0]), GFP_KERNEL);
	vas = kcalloc(nr_vms, sizeof(vas[0]), GFP_KERNEL);
	if (!vas || !vms)
		goto err_free2;

	for (area = 0; area < nr_vms; area++) {
		vas[area] = kzalloc(sizeof(struct vmap_area), GFP_KERNEL);
		vms[area] = kzalloc(sizeof(struct vm_struct), GFP_KERNEL);
		if (!vas[area] || !vms[area])
			goto err_free;
	}
retry:
	spin_lock(&vmap_area_lock);

	/* start scanning - we scan from the top, begin with the last area */
	area = term_area = last_area;
	start = offsets[area];
	end = start + sizes[area];

	if (!pvm_find_next_prev(vmap_area_pcpu_hole, &next, &prev)) {
		base = vmalloc_end - last_end;
		goto found;
	}
	base = pvm_determine_end(&next, &prev, align) - end;

	while (true) {
		BUG_ON(next && next->va_end <= base + end);
		BUG_ON(prev && prev->va_end > base + end);

		/*
		 * base might have underflowed, add last_end before
		 * comparing.
		 */
		if (base + last_end < vmalloc_start + last_end) {
			spin_unlock(&vmap_area_lock);
			if (!purged) {
				purge_vmap_area_lazy();
				purged = true;
				goto retry;
			}
			goto err_free;
		}

		/*
		 * If next overlaps, move base downwards so that it's
		 * right below next and then recheck.
		 */
		if (next && next->va_start < base + end) {
			base = pvm_determine_end(&next, &prev, align) - end;
			term_area = area;
			continue;
		}

		/*
		 * If prev overlaps, shift down next and prev and move
		 * base so that it's right below new next and then
		 * recheck.
		 */
		if (prev && prev->va_end > base + start)  {
			next = prev;
			prev = node_to_va(rb_prev(&next->rb_node));
			base = pvm_determine_end(&next, &prev, align) - end;
			term_area = area;
			continue;
		}

		/*
		 * This area fits, move on to the previous one.  If
		 * the previous one is the terminal one, we're done.
		 */
		area = (area + nr_vms - 1) % nr_vms;
		if (area == term_area)
			break;
		start = offsets[area];
		end = start + sizes[area];
		pvm_find_next_prev(base + end, &next, &prev);
	}
found:
	/* we've found a fitting base, insert all va's */
	for (area = 0; area < nr_vms; area++) {
		struct vmap_area *va = vas[area];

		va->va_start = base + offsets[area];
		va->va_end = va->va_start + sizes[area];
		__insert_vmap_area(va);
	}

	vmap_area_pcpu_hole = base + offsets[last_area];

	spin_unlock(&vmap_area_lock);

	/* insert all vm's */
	for (area = 0; area < nr_vms; area++)
		setup_vmalloc_vm(vms[area], vas[area], VM_ALLOC,
				 pcpu_get_vm_areas);

	kfree(vas);
	return vms;

err_free:
	for (area = 0; area < nr_vms; area++) {
		kfree(vas[area]);
		kfree(vms[area]);
	}
err_free2:
	kfree(vas);
	kfree(vms);
	return NULL;
}

/**
 * pcpu_free_vm_areas - free vmalloc areas for percpu allocator
 * @vms: vm_struct pointer array returned by pcpu_get_vm_areas()
 * @nr_vms: the number of allocated areas
 *
 * Free vm_structs and the array allocated by pcpu_get_vm_areas().
 */
void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
{
	int i;

	for (i = 0; i < nr_vms; i++)
		free_vm_area(vms[i]);
	kfree(vms);
}
#endif	/* CONFIG_SMP */

#ifdef CONFIG_PROC_FS
static void *s_start(struct seq_file *m, loff_t *pos)
	__acquires(&vmap_area_lock)
{
	loff_t n = *pos;
	struct vmap_area *va;

	spin_lock(&vmap_area_lock);
	va = list_first_entry(&vmap_area_list, typeof(*va), list);
	while (n > 0 && &va->list != &vmap_area_list) {
		n--;
		va = list_next_entry(va, list);
	}
	if (!n && &va->list != &vmap_area_list)
		return va;

	return NULL;

}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
	struct vmap_area *va = p, *next;

	++*pos;
	next = list_next_entry(va, list);
	if (&next->list != &vmap_area_list)
		return next;

	return NULL;
}

static void s_stop(struct seq_file *m, void *p)
	__releases(&vmap_area_lock)
{
	spin_unlock(&vmap_area_lock);
}

static void show_numa_info(struct seq_file *m, struct vm_struct *v)
{
	if (IS_ENABLED(CONFIG_NUMA)) {
		unsigned int nr, *counters = m->private;

		if (!counters)
			return;

		if (v->flags & VM_UNINITIALIZED)
			return;
		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
		smp_rmb();

		memset(counters, 0, nr_node_ids * sizeof(unsigned int));

		for (nr = 0; nr < v->nr_pages; nr++)
			counters[page_to_nid(v->pages[nr])]++;

		for_each_node_state(nr, N_HIGH_MEMORY)
			if (counters[nr])
				seq_printf(m, " N%u=%u", nr, counters[nr]);
	}
}

static int s_show(struct seq_file *m, void *p)
{
	struct vmap_area *va = p;
	struct vm_struct *v;

	/*
	 * s_show can encounter race with remove_vm_area, !VM_VM_AREA on
	 * behalf of vmap area is being tear down or vm_map_ram allocation.
	 */
	if (!(va->flags & VM_VM_AREA))
		return 0;

	v = va->vm;

	if (v->flags & VM_LOWMEM)
		return 0;

	seq_printf(m, "0x%pK-0x%pK %7ld",
		v->addr, v->addr + v->size, v->size);

	if (v->caller)
		seq_printf(m, " %pS", v->caller);

	if (v->nr_pages)
		seq_printf(m, " pages=%d", v->nr_pages);

	if (v->phys_addr)
		seq_printf(m, " phys=%llx", (unsigned long long)v->phys_addr);

	if (v->flags & VM_IOREMAP)
		seq_puts(m, " ioremap");

	if (v->flags & VM_ALLOC)
		seq_puts(m, " vmalloc");

	if (v->flags & VM_MAP)
		seq_puts(m, " vmap");

	if (v->flags & VM_USERMAP)
		seq_puts(m, " user");

	if (is_vmalloc_addr(v->pages))
		seq_puts(m, " vpages");

	show_numa_info(m, v);
	seq_putc(m, '\n');
	return 0;
}

static const struct seq_operations vmalloc_op = {
	.start = s_start,
	.next = s_next,
	.stop = s_stop,
	.show = s_show,
};

static int vmalloc_open(struct inode *inode, struct file *file)
{
	if (IS_ENABLED(CONFIG_NUMA))
		return seq_open_private(file, &vmalloc_op,
					nr_node_ids * sizeof(unsigned int));
	else
		return seq_open(file, &vmalloc_op);
}

static const struct file_operations proc_vmalloc_operations = {
	.open		= vmalloc_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release_private,
};

static int __init proc_vmalloc_init(void)
{
	proc_create("vmallocinfo", S_IRUSR, NULL, &proc_vmalloc_operations);
	return 0;
}
module_init(proc_vmalloc_init);

#endif