block: reorganize request fetching functions

[linux-2.6] / 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/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/rbtree.h>
#include <linux/radix-tree.h>
#include <linux/rcupdate.h>
#include <linux/bootmem.h>
#include <linux/pfn.h>

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


/*** 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_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_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)
                        break;
        } while (pgd++, addr = next, addr != end);

        if (unlikely(err))
                return err;
        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;
}

static inline 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));

        if (!pgd_none(*pgd)) {
                pud_t *pud = pud_offset(pgd, addr);
                if (!pud_none(*pud)) {
                        pmd_t *pmd = pmd_offset(pud, addr);
                        if (!pmd_none(*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_LAZY_FREE    0x01
#define VM_LAZY_FREEING 0x02
#define VM_VM_AREA      0x04

struct vmap_area {
        unsigned long va_start;
        unsigned long va_end;
        unsigned long flags;
        struct rb_node rb_node;         /* address sorted rbtree */
        struct list_head list;          /* address sorted list */
        struct list_head purge_list;    /* "lazy purge" list */
        void *private;
        struct rcu_head rcu_head;
};

static DEFINE_SPINLOCK(vmap_area_lock);
static struct rb_root vmap_area_root = RB_ROOT;
static LIST_HEAD(vmap_area_list);

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_start)
                        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;

                parent = *p;
                tmp = rb_entry(parent, struct vmap_area, rb_node);
                if (va->va_start < tmp->va_end)
                        p = &(*p)->rb_left;
                else if (va->va_end > tmp->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 so it is usable like the vmlist */
        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);

/*
 * 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;

        BUG_ON(!size);
        BUG_ON(size & ~PAGE_MASK);

        va = kmalloc_node(sizeof(struct vmap_area),
                        gfp_mask & GFP_RECLAIM_MASK, node);
        if (unlikely(!va))
                return ERR_PTR(-ENOMEM);

retry:
        addr = ALIGN(vstart, align);

        spin_lock(&vmap_area_lock);
        if (addr + size - 1 < addr)
                goto overflow;

        /* XXX: could have a last_hole cache */
        n = vmap_area_root.rb_node;
        if (n) {
                struct vmap_area *first = NULL;

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

                if (!first)
                        goto found;

                if (first->va_end < addr) {
                        n = rb_next(&first->rb_node);
                        if (n)
                                first = rb_entry(n, struct vmap_area, rb_node);
                        else
                                goto found;
                }

                while (addr + size > first->va_start && addr + size <= vend) {
                        addr = ALIGN(first->va_end + PAGE_SIZE, align);
                        if (addr + size - 1 < addr)
                                goto overflow;

                        n = rb_next(&first->rb_node);
                        if (n)
                                first = rb_entry(n, struct vmap_area, rb_node);
                        else
                                goto found;
                }
        }
found:
        if (addr + size > vend) {
overflow:
                spin_unlock(&vmap_area_lock);
                if (!purged) {
                        purge_vmap_area_lazy();
                        purged = 1;
                        goto retry;
                }
                if (printk_ratelimit())
                        printk(KERN_WARNING
                                "vmap allocation for size %lu failed: "
                                "use vmalloc=<size> to increase size.\n", size);
                return ERR_PTR(-EBUSY);
        }

        BUG_ON(addr & (align-1));

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

        return va;
}

static void rcu_free_va(struct rcu_head *head)
{
        struct vmap_area *va = container_of(head, struct vmap_area, rcu_head);

        kfree(va);
}

static void __free_vmap_area(struct vmap_area *va)
{
        BUG_ON(RB_EMPTY_NODE(&va->rb_node));
        rb_erase(&va->rb_node, &vmap_area_root);
        RB_CLEAR_NODE(&va->rb_node);
        list_del_rcu(&va->list);

        call_rcu(&va->rcu_head, rcu_free_va);
}

/*
 * 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
         * CONFIG_DEBUG_PAGEALLOC is set. 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).
         */
#ifdef CONFIG_DEBUG_PAGEALLOC
        vunmap_page_range(start, end);
        flush_tlb_kernel_range(start, end);
#endif
}

/*
 * 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_t vmap_lazy_nr = ATOMIC_INIT(0);

/*
 * Purges all lazily-freed vmap areas.
 *
 * If sync is 0 then don't purge if there is already a purge in progress.
 * If force_flush is 1, then flush kernel TLBs between *start and *end even
 * if we found no lazy vmap areas to unmap (callers can use this to optimise
 * their own TLB flushing).
 * Returns with *start = min(*start, lowest purged address)
 *              *end = max(*end, highest purged address)
 */
static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end,
                                        int sync, int force_flush)
{
        static DEFINE_SPINLOCK(purge_lock);
        LIST_HEAD(valist);
        struct vmap_area *va;
        struct vmap_area *n_va;
        int nr = 0;

        /*
         * If sync is 0 but force_flush is 1, we'll go sync anyway but callers
         * should not expect such behaviour. This just simplifies locking for
         * the case that isn't actually used at the moment anyway.
         */
        if (!sync && !force_flush) {
                if (!spin_trylock(&purge_lock))
                        return;
        } else
                spin_lock(&purge_lock);

        rcu_read_lock();
        list_for_each_entry_rcu(va, &vmap_area_list, list) {
                if (va->flags & VM_LAZY_FREE) {
                        if (va->va_start < *start)
                                *start = va->va_start;
                        if (va->va_end > *end)
                                *end = va->va_end;
                        nr += (va->va_end - va->va_start) >> PAGE_SHIFT;
                        unmap_vmap_area(va);
                        list_add_tail(&va->purge_list, &valist);
                        va->flags |= VM_LAZY_FREEING;
                        va->flags &= ~VM_LAZY_FREE;
                }
        }
        rcu_read_unlock();

        if (nr) {
                BUG_ON(nr > atomic_read(&vmap_lazy_nr));
                atomic_sub(nr, &vmap_lazy_nr);
        }

        if (nr || force_flush)
                flush_tlb_kernel_range(*start, *end);

        if (nr) {
                spin_lock(&vmap_area_lock);
                list_for_each_entry_safe(va, n_va, &valist, purge_list)
                        __free_vmap_area(va);
                spin_unlock(&vmap_area_lock);
        }
        spin_unlock(&purge_lock);
}

/*
 * 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)
{
        unsigned long start = ULONG_MAX, end = 0;

        __purge_vmap_area_lazy(&start, &end, 0, 0);
}

/*
 * Kick off a purge of the outstanding lazy areas.
 */
static void purge_vmap_area_lazy(void)
{
        unsigned long start = ULONG_MAX, end = 0;

        __purge_vmap_area_lazy(&start, &end, 1, 0);
}

/*
 * Free and unmap a vmap area, caller ensuring flush_cache_vunmap had been
 * called for the correct range previously.
 */
static void free_unmap_vmap_area_noflush(struct vmap_area *va)
{
        va->flags |= VM_LAZY_FREE;
        atomic_add((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr);
        if (unlikely(atomic_read(&vmap_lazy_nr) > 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);
        free_unmap_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;
}

static void free_unmap_vmap_area_addr(unsigned long addr)
{
        struct vmap_area *va;

        va = find_vmap_area(addr);
        BUG_ON(!va);
        free_unmap_vmap_area(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 / 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 list_head dirty;
        unsigned int nr_dirty;
};

struct vmap_block {
        spinlock_t lock;
        struct vmap_area *va;
        struct vmap_block_queue *vbq;
        unsigned long free, dirty;
        DECLARE_BITMAP(alloc_map, VMAP_BBMAP_BITS);
        DECLARE_BITMAP(dirty_map, VMAP_BBMAP_BITS);
        union {
                struct list_head free_list;
                struct rcu_head rcu_head;
        };
};

/* 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 struct vmap_block *new_vmap_block(gfp_t gfp_mask)
{
        struct vmap_block_queue *vbq;
        struct vmap_block *vb;
        struct vmap_area *va;
        unsigned long vb_idx;
        int node, err;

        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 (unlikely(IS_ERR(va))) {
                kfree(vb);
                return ERR_PTR(PTR_ERR(va));
        }

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

        spin_lock_init(&vb->lock);
        vb->va = va;
        vb->free = VMAP_BBMAP_BITS;
        vb->dirty = 0;
        bitmap_zero(vb->alloc_map, VMAP_BBMAP_BITS);
        bitmap_zero(vb->dirty_map, VMAP_BBMAP_BITS);
        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);
        vb->vbq = vbq;
        spin_lock(&vbq->lock);
        list_add(&vb->free_list, &vbq->free);
        spin_unlock(&vbq->lock);
        put_cpu_var(vmap_cpu_blocks);

        return vb;
}

static void rcu_free_vb(struct rcu_head *head)
{
        struct vmap_block *vb = container_of(head, struct vmap_block, rcu_head);

        kfree(vb);
}

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

        BUG_ON(!list_empty(&vb->free_list));

        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_unmap_vmap_area_noflush(vb->va);
        call_rcu(&vb->rcu_head, rcu_free_vb);
}

static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
{
        struct vmap_block_queue *vbq;
        struct vmap_block *vb;
        unsigned long addr = 0;
        unsigned int order;

        BUG_ON(size & ~PAGE_MASK);
        BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
        order = get_order(size);

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

                spin_lock(&vb->lock);
                i = bitmap_find_free_region(vb->alloc_map,
                                                VMAP_BBMAP_BITS, order);

                if (i >= 0) {
                        addr = vb->va->va_start + (i << PAGE_SHIFT);
                        BUG_ON(addr_to_vb_idx(addr) !=
                                        addr_to_vb_idx(vb->va->va_start));
                        vb->free -= 1UL << order;
                        if (vb->free == 0) {
                                spin_lock(&vbq->lock);
                                list_del_init(&vb->free_list);
                                spin_unlock(&vbq->lock);
                        }
                        spin_unlock(&vb->lock);
                        break;
                }
                spin_unlock(&vb->lock);
        }
        put_cpu_var(vmap_cpu_blocks);
        rcu_read_unlock();

        if (!addr) {
                vb = new_vmap_block(gfp_mask);
                if (IS_ERR(vb))
                        return vb;
                goto again;
        }

        return (void *)addr;
}

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(size & ~PAGE_MASK);
        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);

        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);

        spin_lock(&vb->lock);
        bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order);

        vb->dirty += 1UL << order;
        if (vb->dirty == VMAP_BBMAP_BITS) {
                BUG_ON(vb->free || !list_empty(&vb->free_list));
                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;

        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) {
                        int i;

                        spin_lock(&vb->lock);
                        i = find_first_bit(vb->dirty_map, VMAP_BBMAP_BITS);
                        while (i < VMAP_BBMAP_BITS) {
                                unsigned long s, e;
                                int j;
                                j = find_next_zero_bit(vb->dirty_map,
                                        VMAP_BBMAP_BITS, i);

                                s = vb->va->va_start + (i << PAGE_SHIFT);
                                e = vb->va->va_start + (j << PAGE_SHIFT);
                                vunmap_page_range(s, e);
                                flush = 1;

                                if (s < start)
                                        start = s;
                                if (e > end)
                                        end = e;

                                i = j;
                                i = find_next_bit(vb->dirty_map,
                                                        VMAP_BBMAP_BITS, i);
                        }
                        spin_unlock(&vb->lock);
                }
                rcu_read_unlock();
        }

        __purge_vmap_area_lazy(&start, &end, 1, 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 = count << PAGE_SHIFT;
        unsigned long addr = (unsigned long)mem;

        BUG_ON(!addr);
        BUG_ON(addr < VMALLOC_START);
        BUG_ON(addr > VMALLOC_END);
        BUG_ON(addr & (PAGE_SIZE-1));

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

        if (likely(count <= VMAP_MAX_ALLOC))
                vb_free(mem, size);
        else
                free_unmap_vmap_area_addr(addr);
}
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
 *
 * 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 = 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);

/**
 * 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->next = vmlist;
        vmlist = 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;

                vbq = &per_cpu(vmap_block_queue, i);
                spin_lock_init(&vbq->lock);
                INIT_LIST_HEAD(&vbq->free);
                INIT_LIST_HEAD(&vbq->dirty);
                vbq->nr_dirty = 0;
        }

        /* Import existing vmlist entries. */
        for (tmp = vmlist; tmp; tmp = tmp->next) {
                va = alloc_bootmem(sizeof(struct vmap_area));
                va->flags = tmp->flags | VM_VM_AREA;
                va->va_start = (unsigned long)tmp->addr;
                va->va_end = va->va_start + tmp->size;
                __insert_vmap_area(va);
        }
        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);
}

/**
 * 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);
}

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 + area->size - PAGE_SIZE;
        int err;

        err = vmap_page_range(addr, end, prot, *pages);
        if (err > 0) {
                *pages += err;
                err = 0;
        }

        return err;
}
EXPORT_SYMBOL_GPL(map_vm_area);

/*** Old vmalloc interfaces ***/
DEFINE_RWLOCK(vmlist_lock);
struct vm_struct *vmlist;

static struct vm_struct *__get_vm_area_node(unsigned long size,
                unsigned long flags, unsigned long start, unsigned long end,
                int node, gfp_t gfp_mask, void *caller)
{
        static struct vmap_area *va;
        struct vm_struct *area;
        struct vm_struct *tmp, **p;
        unsigned long align = 1;

        BUG_ON(in_interrupt());
        if (flags & VM_IOREMAP) {
                int bit = fls(size);

                if (bit > IOREMAP_MAX_ORDER)
                        bit = IOREMAP_MAX_ORDER;
                else if (bit < PAGE_SHIFT)
                        bit = PAGE_SHIFT;

                align = 1ul << bit;
        }

        size = PAGE_ALIGN(size);
        if (unlikely(!size))
                return NULL;

        area = kmalloc_node(sizeof(*area), gfp_mask & GFP_RECLAIM_MASK, node);
        if (unlikely(!area))
                return NULL;

        /*
         * We always allocate a guard page.
         */
        size += PAGE_SIZE;

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

        area->flags = flags;
        area->addr = (void *)va->va_start;
        area->size = size;
        area->pages = NULL;
        area->nr_pages = 0;
        area->phys_addr = 0;
        area->caller = caller;
        va->private = area;
        va->flags |= VM_VM_AREA;

        write_lock(&vmlist_lock);
        for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
                if (tmp->addr >= area->addr)
                        break;
        }
        area->next = *p;
        *p = area;
        write_unlock(&vmlist_lock);

        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, flags, start, end, -1, 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,
                                       void *caller)
{
        return __get_vm_area_node(size, flags, start, end, -1, 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)
{
        return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
                                -1, GFP_KERNEL, __builtin_return_address(0));
}

struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
                                void *caller)
{
        return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
                                                -1, GFP_KERNEL, caller);
}

struct vm_struct *get_vm_area_node(unsigned long size, unsigned long flags,
                                   int node, gfp_t gfp_mask)
{
        return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END, node,
                                  gfp_mask, __builtin_return_address(0));
}

static 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->private;

        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;

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

                vmap_debug_free_range(va->va_start, va->va_end);
                free_unmap_vmap_area(va);
                vm->size -= PAGE_SIZE;

                write_lock(&vmlist_lock);
                for (p = &vmlist; (tmp = *p) != vm; p = &tmp->next)
                        ;
                *p = tmp->next;
                write_unlock(&vmlist_lock);

                return vm;
        }
        return NULL;
}

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

        if (!addr)
                return;

        if ((PAGE_SIZE-1) & (unsigned long)addr) {
                WARN(1, KERN_ERR "Trying to vfree() bad address (%p)\n", addr);
                return;
        }

        area = remove_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, area->size);
        debug_check_no_obj_freed(addr, area->size);

        if (deallocate_pages) {
                int i;

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

                        BUG_ON(!page);
                        __free_page(page);
                }

                if (area->flags & VM_VPAGES)
                        vfree(area->pages);
                else
                        kfree(area->pages);
        }

        kfree(area);
        return;
}

/**
 *      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 interrupt context.
 */
void vfree(const void *addr)
{
        BUG_ON(in_interrupt());
        __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();
        __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;

        might_sleep();

        if (count > num_physpages)
                return NULL;

        area = get_vm_area_caller((count << PAGE_SHIFT), 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, gfp_t gfp_mask, pgprot_t prot,
                            int node, void *caller);
static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
                                 pgprot_t prot, int node, void *caller)
{
        struct page **pages;
        unsigned int nr_pages, array_size, i;

        nr_pages = (area->size - PAGE_SIZE) >> 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, gfp_mask | __GFP_ZERO,
                                PAGE_KERNEL, node, caller);
                area->flags |= VM_VPAGES;
        } else {
                pages = kmalloc_node(array_size,
                                (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
                                node);
        }
        area->pages = pages;
        area->caller = caller;
        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 < 0)
                        page = alloc_page(gfp_mask);
                else
                        page = alloc_pages_node(node, gfp_mask, 0);

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

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

fail:
        vfree(area->addr);
        return NULL;
}

void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot)
{
        return __vmalloc_area_node(area, gfp_mask, prot, -1,
                                        __builtin_return_address(0));
}

/**
 *      __vmalloc_node  -  allocate virtually contiguous memory
 *      @size:          allocation size
 *      @gfp_mask:      flags for the page level allocator
 *      @prot:          protection mask for the allocated pages
 *      @node:          node to use for allocation or -1
 *      @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, gfp_t gfp_mask, pgprot_t prot,
                                                int node, void *caller)
{
        struct vm_struct *area;

        size = PAGE_ALIGN(size);
        if (!size || (size >> PAGE_SHIFT) > num_physpages)
                return NULL;

        area = __get_vm_area_node(size, VM_ALLOC, VMALLOC_START, VMALLOC_END,
                                                node, gfp_mask, caller);

        if (!area)
                return NULL;

        return __vmalloc_area_node(area, gfp_mask, prot, node, caller);
}

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

/**
 *      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(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
                                        -1, __builtin_return_address(0));
}
EXPORT_SYMBOL(vmalloc);

/**
 * 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, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
                             PAGE_KERNEL, -1, __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, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
                                        node, __builtin_return_address(0));
}
EXPORT_SYMBOL(vmalloc_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, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
                              -1, __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, GFP_VMALLOC32, PAGE_KERNEL,
                              -1, __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, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
                             -1, __builtin_return_address(0));
        if (ret) {
                area = find_vm_area(ret);
                area->flags |= VM_USERMAP;
        }
        return ret;
}
EXPORT_SYMBOL(vmalloc_32_user);

long vread(char *buf, char *addr, unsigned long count)
{
        struct vm_struct *tmp;
        char *vaddr, *buf_start = buf;
        unsigned long n;

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

        read_lock(&vmlist_lock);
        for (tmp = vmlist; tmp; tmp = tmp->next) {
                vaddr = (char *) tmp->addr;
                if (addr >= vaddr + tmp->size - PAGE_SIZE)
                        continue;
                while (addr < vaddr) {
                        if (count == 0)
                                goto finished;
                        *buf = '\0';
                        buf++;
                        addr++;
                        count--;
                }
                n = vaddr + tmp->size - PAGE_SIZE - addr;
                do {
                        if (count == 0)
                                goto finished;
                        *buf = *addr;
                        buf++;
                        addr++;
                        count--;
                } while (--n > 0);
        }
finished:
        read_unlock(&vmlist_lock);
        return buf - buf_start;
}

long vwrite(char *buf, char *addr, unsigned long count)
{
        struct vm_struct *tmp;
        char *vaddr, *buf_start = buf;
        unsigned long n;

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

        read_lock(&vmlist_lock);
        for (tmp = vmlist; tmp; tmp = tmp->next) {
                vaddr = (char *) tmp->addr;
                if (addr >= vaddr + tmp->size - PAGE_SIZE)
                        continue;
                while (addr < vaddr) {
                        if (count == 0)
                                goto finished;
                        buf++;
                        addr++;
                        count--;
                }
                n = vaddr + tmp->size - PAGE_SIZE - addr;
                do {
                        if (count == 0)
                                goto finished;
                        *addr = *buf;
                        buf++;
                        addr++;
                        count--;
                } while (--n > 0);
        }
finished:
        read_unlock(&vmlist_lock);
        return buf - buf_start;
}

/**
 *      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)
{
        struct vm_struct *area;
        unsigned long uaddr = vma->vm_start;
        unsigned long usize = vma->vm_end - vma->vm_start;

        if ((PAGE_SIZE-1) & (unsigned long)addr)
                return -EINVAL;

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

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

        if (usize + (pgoff << PAGE_SHIFT) > area->size - PAGE_SIZE)
                return -EINVAL;

        addr += pgoff << PAGE_SHIFT;
        do {
                struct page *page = vmalloc_to_page(addr);
                int ret;

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

                uaddr += PAGE_SIZE;
                addr += PAGE_SIZE;
                usize -= PAGE_SIZE;
        } while (usize > 0);

        /* Prevent "things" like memory migration? VM_flags need a cleanup... */
        vma->vm_flags |= VM_RESERVED;

        return 0;
}
EXPORT_SYMBOL(remap_vmalloc_range);

/*
 * Implement a stub for vmalloc_sync_all() if the architecture chose not to
 * have one.
 */
void  __attribute__((weak)) vmalloc_sync_all(void)
{
}


static int f(pte_t *pte, pgtable_t table, unsigned long addr, void *data)
{
        /* apply_to_page_range() does all the hard work. */
        return 0;
}

/**
 *      alloc_vm_area - allocate a range of kernel address space
 *      @size:          size of the area
 *
 *      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 the kernel address space is not shared
 *      between processes, it syncs the pagetable across all
 *      processes.
 */
struct vm_struct *alloc_vm_area(size_t size)
{
        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,
                                area->size, f, NULL)) {
                free_vm_area(area);
                return NULL;
        }

        /* Make sure the pagetables are constructed in process kernel
           mappings */
        vmalloc_sync_all();

        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_PROC_FS
static void *s_start(struct seq_file *m, loff_t *pos)
{
        loff_t n = *pos;
        struct vm_struct *v;

        read_lock(&vmlist_lock);
        v = vmlist;
        while (n > 0 && v) {
                n--;
                v = v->next;
        }
        if (!n)
                return v;

        return NULL;

}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct vm_struct *v = p;

        ++*pos;
        return v->next;
}

static void s_stop(struct seq_file *m, void *p)
{
        read_unlock(&vmlist_lock);
}

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

                if (!counters)
                        return;

                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 vm_struct *v = p;

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

        if (v->caller) {
                char buff[KSYM_SYMBOL_LEN];

                seq_putc(m, ' ');
                sprint_symbol(buff, (unsigned long)v->caller);
                seq_puts(m, buff);
        }

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

        if (v->phys_addr)
                seq_printf(m, " phys=%lx", v->phys_addr);

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

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

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

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

        if (v->flags & VM_VPAGES)
                seq_printf(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)
{
        unsigned int *ptr = NULL;
        int ret;

        if (NUMA_BUILD)
                ptr = kmalloc(nr_node_ids * sizeof(unsigned int), GFP_KERNEL);
        ret = seq_open(file, &vmalloc_op);
        if (!ret) {
                struct seq_file *m = file->private_data;
                m->private = ptr;
        } else
                kfree(ptr);
        return ret;
}

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