KVM: x86: Allow guests to see MSR_IA32_TSX_CTRL even if tsx=off

[mirror_ubuntu-jammy-kernel.git] / mm / vmalloc.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright (C) 1993  Linus Torvalds
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 *  SMP-safe vmalloc/vfree/ioremap, Tigran Aivazian <tigran@veritas.com>, May 2000
 *  Major rework to support vmap/vunmap, Christoph Hellwig, SGI, August 2002
 *  Numa awareness, Christoph Lameter, SGI, June 2005
 *  Improving global KVA allocator, Uladzislau Rezki, Sony, May 2019
 */

#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/set_memory.h>
#include <linux/debugobjects.h>
#include <linux/kallsyms.h>
#include <linux/list.h>
#include <linux/notifier.h>
#include <linux/rbtree.h>
#include <linux/xarray.h>
#include <linux/rcupdate.h>
#include <linux/pfn.h>
#include <linux/kmemleak.h>
#include <linux/atomic.h>
#include <linux/compiler.h>
#include <linux/llist.h>
#include <linux/bitops.h>
#include <linux/rbtree_augmented.h>
#include <linux/overflow.h>

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

#include "internal.h"
#include "pgalloc-track.h"

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

        return addr >= VMALLOC_START && addr < VMALLOC_END;
}
EXPORT_SYMBOL(is_vmalloc_addr);

struct vfree_deferred {
        struct llist_head list;
        struct work_struct wq;
};
static DEFINE_PER_CPU(struct vfree_deferred, vfree_deferred);

static void __vunmap(const void *, int);

static void free_work(struct work_struct *w)
{
        struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);
        struct llist_node *t, *llnode;

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

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

static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
                             pgtbl_mod_mask *mask)
{
        pte_t *pte;

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

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

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

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

                if (cleared)
                        continue;
                if (pmd_none_or_clear_bad(pmd))
                        continue;
                vunmap_pte_range(pmd, addr, next, mask);

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

static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
                             pgtbl_mod_mask *mask)
{
        pud_t *pud;
        unsigned long next;
        int cleared;

        pud = pud_offset(p4d, addr);
        do {
                next = pud_addr_end(addr, end);

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

                if (cleared)
                        continue;
                if (pud_none_or_clear_bad(pud))
                        continue;
                vunmap_pmd_range(pud, addr, next, mask);
        } while (pud++, addr = next, addr != end);
}

static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
                             pgtbl_mod_mask *mask)
{
        p4d_t *p4d;
        unsigned long next;
        int cleared;

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

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

                if (cleared)
                        continue;
                if (p4d_none_or_clear_bad(p4d))
                        continue;
                vunmap_pud_range(p4d, addr, next, mask);
        } while (p4d++, addr = next, addr != end);
}

/**
 * unmap_kernel_range_noflush - unmap kernel VM area
 * @start: start of the VM area to unmap
 * @size: size of the VM area to unmap
 *
 * Unmap PFN_UP(@size) pages at @addr.  The VM area @addr and @size specify
 * should have been allocated using get_vm_area() and its friends.
 *
 * NOTE:
 * This function does NOT do any cache flushing.  The caller is responsible
 * for calling flush_cache_vunmap() on to-be-mapped areas before calling this
 * function and flush_tlb_kernel_range() after.
 */
void unmap_kernel_range_noflush(unsigned long start, unsigned long size)
{
        unsigned long end = start + size;
        unsigned long next;
        pgd_t *pgd;
        unsigned long addr = start;
        pgtbl_mod_mask mask = 0;

        BUG_ON(addr >= end);
        pgd = pgd_offset_k(addr);
        do {
                next = pgd_addr_end(addr, end);
                if (pgd_bad(*pgd))
                        mask |= PGTBL_PGD_MODIFIED;
                if (pgd_none_or_clear_bad(pgd))
                        continue;
                vunmap_p4d_range(pgd, addr, next, &mask);
        } while (pgd++, addr = next, addr != end);

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

static int vmap_pte_range(pmd_t *pmd, unsigned long addr,
                unsigned long end, pgprot_t prot, struct page **pages, int *nr,
                pgtbl_mod_mask *mask)
{
        pte_t *pte;

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

        pte = pte_alloc_kernel_track(pmd, addr, mask);
        if (!pte)
                return -ENOMEM;
        do {
                struct page *page = pages[*nr];

                if (WARN_ON(!pte_none(*pte)))
                        return -EBUSY;
                if (WARN_ON(!page))
                        return -ENOMEM;
                set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
                (*nr)++;
        } while (pte++, addr += PAGE_SIZE, addr != end);
        *mask |= PGTBL_PTE_MODIFIED;
        return 0;
}

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

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

static int vmap_pud_range(p4d_t *p4d, unsigned long addr,
                unsigned long end, pgprot_t prot, struct page **pages, int *nr,
                pgtbl_mod_mask *mask)
{
        pud_t *pud;
        unsigned long next;

        pud = pud_alloc_track(&init_mm, p4d, addr, mask);
        if (!pud)
                return -ENOMEM;
        do {
                next = pud_addr_end(addr, end);
                if (vmap_pmd_range(pud, addr, next, prot, pages, nr, mask))
                        return -ENOMEM;
        } while (pud++, addr = next, addr != end);
        return 0;
}

static int vmap_p4d_range(pgd_t *pgd, unsigned long addr,
                unsigned long end, pgprot_t prot, struct page **pages, int *nr,
                pgtbl_mod_mask *mask)
{
        p4d_t *p4d;
        unsigned long next;

        p4d = p4d_alloc_track(&init_mm, pgd, addr, mask);
        if (!p4d)
                return -ENOMEM;
        do {
                next = p4d_addr_end(addr, end);
                if (vmap_pud_range(p4d, addr, next, prot, pages, nr, mask))
                        return -ENOMEM;
        } while (p4d++, addr = next, addr != end);
        return 0;
}

/**
 * map_kernel_range_noflush - map kernel VM area with the specified pages
 * @addr: start of the VM area to map
 * @size: size of the VM area to map
 * @prot: page protection flags to use
 * @pages: pages to map
 *
 * Map PFN_UP(@size) pages at @addr.  The VM area @addr and @size specify should
 * have been allocated using get_vm_area() and its friends.
 *
 * NOTE:
 * This function does NOT do any cache flushing.  The caller is responsible for
 * calling flush_cache_vmap() on to-be-mapped areas before calling this
 * function.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
int map_kernel_range_noflush(unsigned long addr, unsigned long size,
                             pgprot_t prot, struct page **pages)
{
        unsigned long start = addr;
        unsigned long end = addr + size;
        unsigned long next;
        pgd_t *pgd;
        int err = 0;
        int nr = 0;
        pgtbl_mod_mask mask = 0;

        BUG_ON(addr >= end);
        pgd = pgd_offset_k(addr);
        do {
                next = pgd_addr_end(addr, end);
                if (pgd_bad(*pgd))
                        mask |= PGTBL_PGD_MODIFIED;
                err = vmap_p4d_range(pgd, addr, next, prot, pages, &nr, &mask);
                if (err)
                        return err;
        } while (pgd++, addr = next, addr != end);

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

        return 0;
}

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

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

int is_vmalloc_or_module_addr(const void *x)
{
        /*
         * ARM, x86-64 and sparc64 put modules in a special place,
         * and fall back on vmalloc() if that fails. Others
         * just put it in the vmalloc space.
         */
#if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
        unsigned long addr = (unsigned long)x;
        if (addr >= MODULES_VADDR && addr < MODULES_END)
                return 1;
#endif
        return is_vmalloc_addr(x);
}

/*
 * Walk a vmap address to the struct page it maps.
 */
struct page *vmalloc_to_page(const void *vmalloc_addr)
{
        unsigned long addr = (unsigned long) vmalloc_addr;
        struct page *page = NULL;
        pgd_t *pgd = pgd_offset_k(addr);
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *ptep, pte;

        /*
         * XXX we might need to change this if we add VIRTUAL_BUG_ON for
         * architectures that do not vmalloc module space
         */
        VIRTUAL_BUG_ON(!is_vmalloc_or_module_addr(vmalloc_addr));

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

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

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

/*
 * Map a vmalloc()-space virtual address to the physical page frame number.
 */
unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
{
        return page_to_pfn(vmalloc_to_page(vmalloc_addr));
}
EXPORT_SYMBOL(vmalloc_to_pfn);


/*** Global kva allocator ***/

#define DEBUG_AUGMENT_PROPAGATE_CHECK 0
#define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0


static DEFINE_SPINLOCK(vmap_area_lock);
static DEFINE_SPINLOCK(free_vmap_area_lock);
/* Export for kexec only */
LIST_HEAD(vmap_area_list);
static struct rb_root vmap_area_root = RB_ROOT;
static bool vmap_initialized __read_mostly;

static struct rb_root purge_vmap_area_root = RB_ROOT;
static LIST_HEAD(purge_vmap_area_list);
static DEFINE_SPINLOCK(purge_vmap_area_lock);

/*
 * This kmem_cache is used for vmap_area objects. Instead of
 * allocating from slab we reuse an object from this cache to
 * make things faster. Especially in "no edge" splitting of
 * free block.
 */
static struct kmem_cache *vmap_area_cachep;

/*
 * This linked list is used in pair with free_vmap_area_root.
 * It gives O(1) access to prev/next to perform fast coalescing.
 */
static LIST_HEAD(free_vmap_area_list);

/*
 * This augment red-black tree represents the free vmap space.
 * All vmap_area objects in this tree are sorted by va->va_start
 * address. It is used for allocation and merging when a vmap
 * object is released.
 *
 * Each vmap_area node contains a maximum available free block
 * of its sub-tree, right or left. Therefore it is possible to
 * find a lowest match of free area.
 */
static struct rb_root free_vmap_area_root = RB_ROOT;

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

static __always_inline unsigned long
va_size(struct vmap_area *va)
{
        return (va->va_end - va->va_start);
}

static __always_inline unsigned long
get_subtree_max_size(struct rb_node *node)
{
        struct vmap_area *va;

        va = rb_entry_safe(node, struct vmap_area, rb_node);
        return va ? va->subtree_max_size : 0;
}

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

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

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

static atomic_long_t nr_vmalloc_pages;

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

static struct vmap_area *__find_vmap_area(unsigned long addr)
{
        struct rb_node *n = vmap_area_root.rb_node;

        while (n) {
                struct vmap_area *va;

                va = rb_entry(n, struct vmap_area, rb_node);
                if (addr < va->va_start)
                        n = n->rb_left;
                else if (addr >= va->va_end)
                        n = n->rb_right;
                else
                        return va;
        }

        return NULL;
}

/*
 * This function returns back addresses of parent node
 * and its left or right link for further processing.
 *
 * Otherwise NULL is returned. In that case all further
 * steps regarding inserting of conflicting overlap range
 * have to be declined and actually considered as a bug.
 */
static __always_inline struct rb_node **
find_va_links(struct vmap_area *va,
        struct rb_root *root, struct rb_node *from,
        struct rb_node **parent)
{
        struct vmap_area *tmp_va;
        struct rb_node **link;

        if (root) {
                link = &root->rb_node;
                if (unlikely(!*link)) {
                        *parent = NULL;
                        return link;
                }
        } else {
                link = &from;
        }

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

                /*
                 * During the traversal we also do some sanity check.
                 * Trigger the BUG() if there are sides(left/right)
                 * or full overlaps.
                 */
                if (va->va_start < tmp_va->va_end &&
                                va->va_end <= tmp_va->va_start)
                        link = &(*link)->rb_left;
                else if (va->va_end > tmp_va->va_start &&
                                va->va_start >= tmp_va->va_end)
                        link = &(*link)->rb_right;
                else {
                        WARN(1, "vmalloc bug: 0x%lx-0x%lx overlaps with 0x%lx-0x%lx\n",
                                va->va_start, va->va_end, tmp_va->va_start, tmp_va->va_end);

                        return NULL;
                }
        } while (*link);

        *parent = &tmp_va->rb_node;
        return link;
}

static __always_inline struct list_head *
get_va_next_sibling(struct rb_node *parent, struct rb_node **link)
{
        struct list_head *list;

        if (unlikely(!parent))
                /*
                 * The red-black tree where we try to find VA neighbors
                 * before merging or inserting is empty, i.e. it means
                 * there is no free vmap space. Normally it does not
                 * happen but we handle this case anyway.
                 */
                return NULL;

        list = &rb_entry(parent, struct vmap_area, rb_node)->list;
        return (&parent->rb_right == link ? list->next : list);
}

static __always_inline void
link_va(struct vmap_area *va, struct rb_root *root,
        struct rb_node *parent, struct rb_node **link, struct list_head *head)
{
        /*
         * VA is still not in the list, but we can
         * identify its future previous list_head node.
         */
        if (likely(parent)) {
                head = &rb_entry(parent, struct vmap_area, rb_node)->list;
                if (&parent->rb_right != link)
                        head = head->prev;
        }

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

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

static __always_inline void
unlink_va(struct vmap_area *va, struct rb_root *root)
{
        if (WARN_ON(RB_EMPTY_NODE(&va->rb_node)))
                return;

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

        list_del(&va->list);
        RB_CLEAR_NODE(&va->rb_node);
}

#if DEBUG_AUGMENT_PROPAGATE_CHECK
static void
augment_tree_propagate_check(void)
{
        struct vmap_area *va;
        unsigned long computed_size;

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

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

#if DEBUG_AUGMENT_PROPAGATE_CHECK
        augment_tree_propagate_check();
#endif
}

static void
insert_vmap_area(struct vmap_area *va,
        struct rb_root *root, struct list_head *head)
{
        struct rb_node **link;
        struct rb_node *parent;

        link = find_va_links(va, root, NULL, &parent);
        if (link)
                link_va(va, root, parent, link, head);
}

static void
insert_vmap_area_augment(struct vmap_area *va,
        struct rb_node *from, struct rb_root *root,
        struct list_head *head)
{
        struct rb_node **link;
        struct rb_node *parent;

        if (from)
                link = find_va_links(va, NULL, from, &parent);
        else
                link = find_va_links(va, root, NULL, &parent);

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

/*
 * Merge de-allocated chunk of VA memory with previous
 * and next free blocks. If coalesce is not done a new
 * free area is inserted. If VA has been merged, it is
 * freed.
 *
 * Please note, it can return NULL in case of overlap
 * ranges, followed by WARN() report. Despite it is a
 * buggy behaviour, a system can be alive and keep
 * ongoing.
 */
static __always_inline struct vmap_area *
merge_or_add_vmap_area(struct vmap_area *va,
        struct rb_root *root, struct list_head *head)
{
        struct vmap_area *sibling;
        struct list_head *next;
        struct rb_node **link;
        struct rb_node *parent;
        bool merged = false;

        /*
         * Find a place in the tree where VA potentially will be
         * inserted, unless it is merged with its sibling/siblings.
         */
        link = find_va_links(va, root, NULL, &parent);
        if (!link)
                return NULL;

        /*
         * Get next node of VA to check if merging can be done.
         */
        next = get_va_next_sibling(parent, link);
        if (unlikely(next == NULL))
                goto insert;

        /*
         * start            end
         * |                |
         * |<------VA------>|<-----Next----->|
         *                  |                |
         *                  start            end
         */
        if (next != head) {
                sibling = list_entry(next, struct vmap_area, list);
                if (sibling->va_start == va->va_end) {
                        sibling->va_start = va->va_start;

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

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

        /*
         * start            end
         * |                |
         * |<-----Prev----->|<------VA------>|
         *                  |                |
         *                  start            end
         */
        if (next->prev != head) {
                sibling = list_entry(next->prev, struct vmap_area, list);
                if (sibling->va_end == va->va_start) {
                        /*
                         * If both neighbors are coalesced, it is important
                         * to unlink the "next" node first, followed by merging
                         * with "previous" one. Otherwise the tree might not be
                         * fully populated if a sibling's augmented value is
                         * "normalized" because of rotation operations.
                         */
                        if (merged)
                                unlink_va(va, root);

                        sibling->va_end = va->va_end;

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

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

insert:
        if (!merged)
                link_va(va, root, parent, link, head);

        return va;
}

static __always_inline struct vmap_area *
merge_or_add_vmap_area_augment(struct vmap_area *va,
        struct rb_root *root, struct list_head *head)
{
        va = merge_or_add_vmap_area(va, root, head);
        if (va)
                augment_tree_propagate_from(va);

        return va;
}

static __always_inline bool
is_within_this_va(struct vmap_area *va, unsigned long size,
        unsigned long align, unsigned long vstart)
{
        unsigned long nva_start_addr;

        if (va->va_start > vstart)
                nva_start_addr = ALIGN(va->va_start, align);
        else
                nva_start_addr = ALIGN(vstart, align);

        /* Can be overflowed due to big size or alignment. */
        if (nva_start_addr + size < nva_start_addr ||
                        nva_start_addr < vstart)
                return false;

        return (nva_start_addr + size <= va->va_end);
}

/*
 * Find the first free block(lowest start address) in the tree,
 * that will accomplish the request corresponding to passing
 * parameters.
 */
static __always_inline struct vmap_area *
find_vmap_lowest_match(unsigned long size,
        unsigned long align, unsigned long vstart)
{
        struct vmap_area *va;
        struct rb_node *node;
        unsigned long length;

        /* Start from the root. */
        node = free_vmap_area_root.rb_node;

        /* Adjust the search size for alignment overhead. */
        length = size + align - 1;

        while (node) {
                va = rb_entry(node, struct vmap_area, rb_node);

                if (get_subtree_max_size(node->rb_left) >= length &&
                                vstart < va->va_start) {
                        node = node->rb_left;
                } else {
                        if (is_within_this_va(va, size, align, vstart))
                                return va;

                        /*
                         * Does not make sense to go deeper towards the right
                         * sub-tree if it does not have a free block that is
                         * equal or bigger to the requested search length.
                         */
                        if (get_subtree_max_size(node->rb_right) >= length) {
                                node = node->rb_right;
                                continue;
                        }

                        /*
                         * OK. We roll back and find the first right sub-tree,
                         * that will satisfy the search criteria. It can happen
                         * only once due to "vstart" restriction.
                         */
                        while ((node = rb_parent(node))) {
                                va = rb_entry(node, struct vmap_area, rb_node);
                                if (is_within_this_va(va, size, align, vstart))
                                        return va;

                                if (get_subtree_max_size(node->rb_right) >= length &&
                                                vstart <= va->va_start) {
                                        node = node->rb_right;
                                        break;
                                }
                        }
                }
        }

        return NULL;
}

#if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
#include <linux/random.h>

static struct vmap_area *
find_vmap_lowest_linear_match(unsigned long size,
        unsigned long align, unsigned long vstart)
{
        struct vmap_area *va;

        list_for_each_entry(va, &free_vmap_area_list, list) {
                if (!is_within_this_va(va, size, align, vstart))
                        continue;

                return va;
        }

        return NULL;
}

static void
find_vmap_lowest_match_check(unsigned long size)
{
        struct vmap_area *va_1, *va_2;
        unsigned long vstart;
        unsigned int rnd;

        get_random_bytes(&rnd, sizeof(rnd));
        vstart = VMALLOC_START + rnd;

        va_1 = find_vmap_lowest_match(size, 1, vstart);
        va_2 = find_vmap_lowest_linear_match(size, 1, vstart);

        if (va_1 != va_2)
                pr_emerg("not lowest: t: 0x%p, l: 0x%p, v: 0x%lx\n",
                        va_1, va_2, vstart);
}
#endif

enum fit_type {
        NOTHING_FIT = 0,
        FL_FIT_TYPE = 1,        /* full fit */
        LE_FIT_TYPE = 2,        /* left edge fit */
        RE_FIT_TYPE = 3,        /* right edge fit */
        NE_FIT_TYPE = 4         /* no edge fit */
};

static __always_inline enum fit_type
classify_va_fit_type(struct vmap_area *va,
        unsigned long nva_start_addr, unsigned long size)
{
        enum fit_type type;

        /* Check if it is within VA. */
        if (nva_start_addr < va->va_start ||
                        nva_start_addr + size > va->va_end)
                return NOTHING_FIT;

        /* Now classify. */
        if (va->va_start == nva_start_addr) {
                if (va->va_end == nva_start_addr + size)
                        type = FL_FIT_TYPE;
                else
                        type = LE_FIT_TYPE;
        } else if (va->va_end == nva_start_addr + size) {
                type = RE_FIT_TYPE;
        } else {
                type = NE_FIT_TYPE;
        }

        return type;
}

static __always_inline int
adjust_va_to_fit_type(struct vmap_area *va,
        unsigned long nva_start_addr, unsigned long size,
        enum fit_type type)
{
        struct vmap_area *lva = NULL;

        if (type == FL_FIT_TYPE) {
                /*
                 * No need to split VA, it fully fits.
                 *
                 * |               |
                 * V      NVA      V
                 * |---------------|
                 */
                unlink_va(va, &free_vmap_area_root);
                kmem_cache_free(vmap_area_cachep, va);
        } else if (type == LE_FIT_TYPE) {
                /*
                 * Split left edge of fit VA.
                 *
                 * |       |
                 * V  NVA  V   R
                 * |-------|-------|
                 */
                va->va_start += size;
        } else if (type == RE_FIT_TYPE) {
                /*
                 * Split right edge of fit VA.
                 *
                 *         |       |
                 *     L   V  NVA  V
                 * |-------|-------|
                 */
                va->va_end = nva_start_addr;
        } else if (type == NE_FIT_TYPE) {
                /*
                 * Split no edge of fit VA.
                 *
                 *     |       |
                 *   L V  NVA  V R
                 * |---|-------|---|
                 */
                lva = __this_cpu_xchg(ne_fit_preload_node, NULL);
                if (unlikely(!lva)) {
                        /*
                         * For percpu allocator we do not do any pre-allocation
                         * and leave it as it is. The reason is it most likely
                         * never ends up with NE_FIT_TYPE splitting. In case of
                         * percpu allocations offsets and sizes are aligned to
                         * fixed align request, i.e. RE_FIT_TYPE and FL_FIT_TYPE
                         * are its main fitting cases.
                         *
                         * There are a few exceptions though, as an example it is
                         * a first allocation (early boot up) when we have "one"
                         * big free space that has to be split.
                         *
                         * Also we can hit this path in case of regular "vmap"
                         * allocations, if "this" current CPU was not preloaded.
                         * See the comment in alloc_vmap_area() why. If so, then
                         * GFP_NOWAIT is used instead to get an extra object for
                         * split purpose. That is rare and most time does not
                         * occur.
                         *
                         * What happens if an allocation gets failed. Basically,
                         * an "overflow" path is triggered to purge lazily freed
                         * areas to free some memory, then, the "retry" path is
                         * triggered to repeat one more time. See more details
                         * in alloc_vmap_area() function.
                         */
                        lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT);
                        if (!lva)
                                return -1;
                }

                /*
                 * Build the remainder.
                 */
                lva->va_start = va->va_start;
                lva->va_end = nva_start_addr;

                /*
                 * Shrink this VA to remaining size.
                 */
                va->va_start = nva_start_addr + size;
        } else {
                return -1;
        }

        if (type != FL_FIT_TYPE) {
                augment_tree_propagate_from(va);

                if (lva)        /* type == NE_FIT_TYPE */
                        insert_vmap_area_augment(lva, &va->rb_node,
                                &free_vmap_area_root, &free_vmap_area_list);
        }

        return 0;
}

/*
 * Returns a start address of the newly allocated area, if success.
 * Otherwise a vend is returned that indicates failure.
 */
static __always_inline unsigned long
__alloc_vmap_area(unsigned long size, unsigned long align,
        unsigned long vstart, unsigned long vend)
{
        unsigned long nva_start_addr;
        struct vmap_area *va;
        enum fit_type type;
        int ret;

        va = find_vmap_lowest_match(size, align, vstart);
        if (unlikely(!va))
                return vend;

        if (va->va_start > vstart)
                nva_start_addr = ALIGN(va->va_start, align);
        else
                nva_start_addr = ALIGN(vstart, align);

        /* Check the "vend" restriction. */
        if (nva_start_addr + size > vend)
                return vend;

        /* Classify what we have found. */
        type = classify_va_fit_type(va, nva_start_addr, size);
        if (WARN_ON_ONCE(type == NOTHING_FIT))
                return vend;

        /* Update the free vmap_area. */
        ret = adjust_va_to_fit_type(va, nva_start_addr, size, type);
        if (ret)
                return vend;

#if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
        find_vmap_lowest_match_check(size);
#endif

        return nva_start_addr;
}

/*
 * Free a region of KVA allocated by alloc_vmap_area
 */
static void free_vmap_area(struct vmap_area *va)
{
        /*
         * Remove from the busy tree/list.
         */
        spin_lock(&vmap_area_lock);
        unlink_va(va, &vmap_area_root);
        spin_unlock(&vmap_area_lock);

        /*
         * Insert/Merge it back to the free tree/list.
         */
        spin_lock(&free_vmap_area_lock);
        merge_or_add_vmap_area_augment(va, &free_vmap_area_root, &free_vmap_area_list);
        spin_unlock(&free_vmap_area_lock);
}

/*
 * Allocate a region of KVA of the specified size and alignment, within the
 * vstart and vend.
 */
static struct vmap_area *alloc_vmap_area(unsigned long size,
                                unsigned long align,
                                unsigned long vstart, unsigned long vend,
                                int node, gfp_t gfp_mask)
{
        struct vmap_area *va, *pva;
        unsigned long addr;
        int purged = 0;
        int ret;

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

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

        might_sleep();
        gfp_mask = gfp_mask & GFP_RECLAIM_MASK;

        va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
        if (unlikely(!va))
                return ERR_PTR(-ENOMEM);

        /*
         * Only scan the relevant parts containing pointers to other objects
         * to avoid false negatives.
         */
        kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask);

retry:
        /*
         * Preload this CPU with one extra vmap_area object. It is used
         * when fit type of free area is NE_FIT_TYPE. Please note, it
         * does not guarantee that an allocation occurs on a CPU that
         * is preloaded, instead we minimize the case when it is not.
         * It can happen because of cpu migration, because there is a
         * race until the below spinlock is taken.
         *
         * The preload is done in non-atomic context, thus it allows us
         * to use more permissive allocation masks to be more stable under
         * low memory condition and high memory pressure. In rare case,
         * if not preloaded, GFP_NOWAIT is used.
         *
         * Set "pva" to NULL here, because of "retry" path.
         */
        pva = NULL;

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

        spin_lock(&free_vmap_area_lock);

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

        /*
         * If an allocation fails, the "vend" address is
         * returned. Therefore trigger the overflow path.
         */
        addr = __alloc_vmap_area(size, align, vstart, vend);
        spin_unlock(&free_vmap_area_lock);

        if (unlikely(addr == vend))
                goto overflow;

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


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

        BUG_ON(!IS_ALIGNED(va->va_start, align));
        BUG_ON(va->va_start < vstart);
        BUG_ON(va->va_end > vend);

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

        return va;

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

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

        if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
                pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
                        size);

        kmem_cache_free(vmap_area_cachep, va);
        return ERR_PTR(-EBUSY);
}

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

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

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

        log = fls(num_online_cpus());

        return log * (32UL * 1024 * 1024 / PAGE_SIZE);
}

static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0);

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

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

/*
 * called before a call to iounmap() if the caller wants vm_area_struct's
 * immediately freed.
 */
void set_iounmap_nonlazy(void)
{
        atomic_long_set(&vmap_lazy_nr, lazy_max_pages()+1);
}

/*
 * Purges all lazily-freed vmap areas.
 */
static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
{
        unsigned long resched_threshold;
        struct list_head local_pure_list;
        struct vmap_area *va, *n_va;

        lockdep_assert_held(&vmap_purge_lock);

        spin_lock(&purge_vmap_area_lock);
        purge_vmap_area_root = RB_ROOT;
        list_replace_init(&purge_vmap_area_list, &local_pure_list);
        spin_unlock(&purge_vmap_area_lock);

        if (unlikely(list_empty(&local_pure_list)))
                return false;

        start = min(start,
                list_first_entry(&local_pure_list,
                        struct vmap_area, list)->va_start);

        end = max(end,
                list_last_entry(&local_pure_list,
                        struct vmap_area, list)->va_end);

        flush_tlb_kernel_range(start, end);
        resched_threshold = lazy_max_pages() << 1;

        spin_lock(&free_vmap_area_lock);
        list_for_each_entry_safe(va, n_va, &local_pure_list, list) {
                unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT;
                unsigned long orig_start = va->va_start;
                unsigned long orig_end = va->va_end;

                /*
                 * Finally insert or merge lazily-freed area. It is
                 * detached and there is no need to "unlink" it from
                 * anything.
                 */
                va = merge_or_add_vmap_area_augment(va, &free_vmap_area_root,
                                &free_vmap_area_list);

                if (!va)
                        continue;

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

                atomic_long_sub(nr, &vmap_lazy_nr);

                if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)
                        cond_resched_lock(&free_vmap_area_lock);
        }
        spin_unlock(&free_vmap_area_lock);
        return true;
}

/*
 * Kick off a purge of the outstanding lazy areas. Don't bother if somebody
 * is already purging.
 */
static void try_purge_vmap_area_lazy(void)
{
        if (mutex_trylock(&vmap_purge_lock)) {
                __purge_vmap_area_lazy(ULONG_MAX, 0);
                mutex_unlock(&vmap_purge_lock);
        }
}

/*
 * Kick off a purge of the outstanding lazy areas.
 */
static void purge_vmap_area_lazy(void)
{
        mutex_lock(&vmap_purge_lock);
        purge_fragmented_blocks_allcpus();
        __purge_vmap_area_lazy(ULONG_MAX, 0);
        mutex_unlock(&vmap_purge_lock);
}

/*
 * Free a vmap area, caller ensuring that the area has been unmapped
 * and flush_cache_vunmap had been called for the correct range
 * previously.
 */
static void free_vmap_area_noflush(struct vmap_area *va)
{
        unsigned long nr_lazy;

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

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

        /*
         * Merge or place it to the purge tree/list.
         */
        spin_lock(&purge_vmap_area_lock);
        merge_or_add_vmap_area(va,
                &purge_vmap_area_root, &purge_vmap_area_list);
        spin_unlock(&purge_vmap_area_lock);

        /* After this point, we may free va at any time */
        if (unlikely(nr_lazy > lazy_max_pages()))
                try_purge_vmap_area_lazy();
}

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

        free_vmap_area_noflush(va);
}

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

        spin_lock(&vmap_area_lock);
        va = __find_vmap_area(addr);
        spin_unlock(&vmap_area_lock);

        return va;
}

/*** Per cpu kva allocator ***/

/*
 * vmap space is limited especially on 32 bit architectures. Ensure there is
 * room for at least 16 percpu vmap blocks per CPU.
 */
/*
 * If we had a constant VMALLOC_START and VMALLOC_END, we'd like to be able
 * to #define VMALLOC_SPACE             (VMALLOC_END-VMALLOC_START). Guess
 * instead (we just need a rough idea)
 */
#if BITS_PER_LONG == 32
#define VMALLOC_SPACE           (128UL*1024*1024)
#else
#define VMALLOC_SPACE           (128UL*1024*1024*1024)
#endif

#define VMALLOC_PAGES           (VMALLOC_SPACE / PAGE_SIZE)
#define VMAP_MAX_ALLOC          BITS_PER_LONG   /* 256K with 4K pages */
#define VMAP_BBMAP_BITS_MAX     1024    /* 4MB with 4K pages */
#define VMAP_BBMAP_BITS_MIN     (VMAP_MAX_ALLOC*2)
#define VMAP_MIN(x, y)          ((x) < (y) ? (x) : (y)) /* can't use min() */
#define VMAP_MAX(x, y)          ((x) > (y) ? (x) : (y)) /* can't use max() */
#define VMAP_BBMAP_BITS         \
                VMAP_MIN(VMAP_BBMAP_BITS_MAX,   \
                VMAP_MAX(VMAP_BBMAP_BITS_MIN,   \
                        VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16))

#define VMAP_BLOCK_SIZE         (VMAP_BBMAP_BITS * PAGE_SIZE)

struct vmap_block_queue {
        spinlock_t lock;
        struct list_head free;
};

struct vmap_block {
        spinlock_t lock;
        struct vmap_area *va;
        unsigned long free, dirty;
        unsigned long dirty_min, dirty_max; /*< dirty range */
        struct list_head free_list;
        struct rcu_head rcu_head;
        struct list_head purge;
};

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

/*
 * XArray of vmap blocks, indexed by address, to quickly find a vmap block
 * in the free path. Could get rid of this if we change the API to return a
 * "cookie" from alloc, to be passed to free. But no big deal yet.
 */
static DEFINE_XARRAY(vmap_blocks);

/*
 * We should probably have a fallback mechanism to allocate virtual memory
 * out of partially filled vmap blocks. However vmap block sizing should be
 * fairly reasonable according to the vmalloc size, so it shouldn't be a
 * big problem.
 */

static unsigned long addr_to_vb_idx(unsigned long addr)
{
        addr -= VMALLOC_START & ~(VMAP_BLOCK_SIZE-1);
        addr /= VMAP_BLOCK_SIZE;
        return addr;
}

static void *vmap_block_vaddr(unsigned long va_start, unsigned long pages_off)
{
        unsigned long addr;

        addr = va_start + (pages_off << PAGE_SHIFT);
        BUG_ON(addr_to_vb_idx(addr) != addr_to_vb_idx(va_start));
        return (void *)addr;
}

/**
 * new_vmap_block - allocates new vmap_block and occupies 2^order pages in this
 *                  block. Of course pages number can't exceed VMAP_BBMAP_BITS
 * @order:    how many 2^order pages should be occupied in newly allocated block
 * @gfp_mask: flags for the page level allocator
 *
 * Return: virtual address in a newly allocated block or ERR_PTR(-errno)
 */
static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
{
        struct vmap_block_queue *vbq;
        struct vmap_block *vb;
        struct vmap_area *va;
        unsigned long vb_idx;
        int node, err;
        void *vaddr;

        node = numa_node_id();

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

        va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
                                        VMALLOC_START, VMALLOC_END,
                                        node, gfp_mask);
        if (IS_ERR(va)) {
                kfree(vb);
                return ERR_CAST(va);
        }

        vaddr = vmap_block_vaddr(va->va_start, 0);
        spin_lock_init(&vb->lock);
        vb->va = va;
        /* At least something should be left free */
        BUG_ON(VMAP_BBMAP_BITS <= (1UL << order));
        vb->free = VMAP_BBMAP_BITS - (1UL << order);
        vb->dirty = 0;
        vb->dirty_min = VMAP_BBMAP_BITS;
        vb->dirty_max = 0;
        INIT_LIST_HEAD(&vb->free_list);

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

        vbq = &get_cpu_var(vmap_block_queue);
        spin_lock(&vbq->lock);
        list_add_tail_rcu(&vb->free_list, &vbq->free);
        spin_unlock(&vbq->lock);
        put_cpu_var(vmap_block_queue);

        return vaddr;
}

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

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

        free_vmap_area_noflush(vb->va);
        kfree_rcu(vb, rcu_head);
}

static void purge_fragmented_blocks(int cpu)
{
        LIST_HEAD(purge);
        struct vmap_block *vb;
        struct vmap_block *n_vb;
        struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);

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

                if (!(vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS))
                        continue;

                spin_lock(&vb->lock);
                if (vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS) {
                        vb->free = 0; /* prevent further allocs after releasing lock */
                        vb->dirty = VMAP_BBMAP_BITS; /* prevent purging it again */
                        vb->dirty_min = 0;
                        vb->dirty_max = VMAP_BBMAP_BITS;
                        spin_lock(&vbq->lock);
                        list_del_rcu(&vb->free_list);
                        spin_unlock(&vbq->lock);
                        spin_unlock(&vb->lock);
                        list_add_tail(&vb->purge, &purge);
                } else
                        spin_unlock(&vb->lock);
        }
        rcu_read_unlock();

        list_for_each_entry_safe(vb, n_vb, &purge, purge) {
                list_del(&vb->purge);
                free_vmap_block(vb);
        }
}

static void purge_fragmented_blocks_allcpus(void)
{
        int cpu;

        for_each_possible_cpu(cpu)
                purge_fragmented_blocks(cpu);
}

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

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

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

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

                pages_off = VMAP_BBMAP_BITS - vb->free;
                vaddr = vmap_block_vaddr(vb->va->va_start, pages_off);
                vb->free -= 1UL << order;
                if (vb->free == 0) {
                        spin_lock(&vbq->lock);
                        list_del_rcu(&vb->free_list);
                        spin_unlock(&vbq->lock);
                }

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

        put_cpu_var(vmap_block_queue);
        rcu_read_unlock();

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

        return vaddr;
}

static void vb_free(unsigned long addr, unsigned long size)
{
        unsigned long offset;
        unsigned int order;
        struct vmap_block *vb;

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

        flush_cache_vunmap(addr, addr + size);

        order = get_order(size);
        offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
        vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr));

        unmap_kernel_range_noflush(addr, size);

        if (debug_pagealloc_enabled_static())
                flush_tlb_kernel_range(addr, addr + size);

        spin_lock(&vb->lock);

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

        vb->dirty += 1UL << order;
        if (vb->dirty == VMAP_BBMAP_BITS) {
                BUG_ON(vb->free);
                spin_unlock(&vb->lock);
                free_vmap_block(vb);
        } else
                spin_unlock(&vb->lock);
}

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

        if (unlikely(!vmap_initialized))
                return;

        might_sleep();

        for_each_possible_cpu(cpu) {
                struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
                struct vmap_block *vb;

                rcu_read_lock();
                list_for_each_entry_rcu(vb, &vbq->free, free_list) {
                        spin_lock(&vb->lock);
                        if (vb->dirty) {
                                unsigned long va_start = vb->va->va_start;
                                unsigned long s, e;

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

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

                                flush = 1;
                        }
                        spin_unlock(&vb->lock);
                }
                rcu_read_unlock();
        }

        mutex_lock(&vmap_purge_lock);
        purge_fragmented_blocks_allcpus();
        if (!__purge_vmap_area_lazy(start, end) && flush)
                flush_tlb_kernel_range(start, end);
        mutex_unlock(&vmap_purge_lock);
}

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

        _vm_unmap_aliases(start, end, flush);
}
EXPORT_SYMBOL_GPL(vm_unmap_aliases);

/**
 * vm_unmap_ram - unmap linear kernel address space set up by vm_map_ram
 * @mem: the pointer returned by vm_map_ram
 * @count: the count passed to that vm_map_ram call (cannot unmap partial)
 */
void vm_unmap_ram(const void *mem, unsigned int count)
{
        unsigned long size = (unsigned long)count << PAGE_SHIFT;
        unsigned long addr = (unsigned long)mem;
        struct vmap_area *va;

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

        kasan_poison_vmalloc(mem, size);

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

        va = find_vmap_area(addr);
        BUG_ON(!va);
        debug_check_no_locks_freed((void *)va->va_start,
                                    (va->va_end - va->va_start));
        free_unmap_vmap_area(va);
}
EXPORT_SYMBOL(vm_unmap_ram);

/**
 * vm_map_ram - map pages linearly into kernel virtual address (vmalloc space)
 * @pages: an array of pointers to the pages to be mapped
 * @count: number of pages
 * @node: prefer to allocate data structures on this node
 *
 * If you use this function for less than VMAP_MAX_ALLOC pages, it could be
 * faster than vmap so it's good.  But if you mix long-life and short-life
 * objects with vm_map_ram(), it could consume lots of address space through
 * fragmentation (especially on a 32bit machine).  You could see failures in
 * the end.  Please use this function for short-lived objects.
 *
 * Returns: a pointer to the address that has been mapped, or %NULL on failure
 */
void *vm_map_ram(struct page **pages, unsigned int count, int node)
{
        unsigned long size = (unsigned long)count << PAGE_SHIFT;
        unsigned long addr;
        void *mem;

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

                addr = va->va_start;
                mem = (void *)addr;
        }

        kasan_unpoison_vmalloc(mem, size);

        if (map_kernel_range(addr, size, PAGE_KERNEL, pages) < 0) {
                vm_unmap_ram(mem, count);
                return NULL;
        }
        return mem;
}
EXPORT_SYMBOL(vm_map_ram);

static struct vm_struct *vmlist __initdata;

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

        BUG_ON(vmap_initialized);
        for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
                if (tmp->addr >= vm->addr) {
                        BUG_ON(tmp->addr < vm->addr + vm->size);
                        break;
                } else
                        BUG_ON(tmp->addr + tmp->size > vm->addr);
        }
        vm->next = *p;
        *p = vm;
}

/**
 * vm_area_register_early - register vmap area early during boot
 * @vm: vm_struct to register
 * @align: requested alignment
 *
 * This function is used to register kernel vm area before
 * vmalloc_init() is called.  @vm->size and @vm->flags should contain
 * proper values on entry and other fields should be zero.  On return,
 * vm->addr contains the allocated address.
 *
 * DO NOT USE THIS FUNCTION UNLESS YOU KNOW WHAT YOU'RE DOING.
 */
void __init vm_area_register_early(struct vm_struct *vm, size_t align)
{
        static size_t vm_init_off __initdata;
        unsigned long addr;

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

        vm->addr = (void *)addr;

        vm_area_add_early(vm);
}

static void vmap_init_free_space(void)
{
        unsigned long vmap_start = 1;
        const unsigned long vmap_end = ULONG_MAX;
        struct vmap_area *busy, *free;

        /*
         *     B     F     B     B     B     F
         * -|-----|.....|-----|-----|-----|.....|-
         *  |           The KVA space           |
         *  |<--------------------------------->|
         */
        list_for_each_entry(busy, &vmap_area_list, list) {
                if (busy->va_start - vmap_start > 0) {
                        free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
                        if (!WARN_ON_ONCE(!free)) {
                                free->va_start = vmap_start;
                                free->va_end = busy->va_start;

                                insert_vmap_area_augment(free, NULL,
                                        &free_vmap_area_root,
                                                &free_vmap_area_list);
                        }
                }

                vmap_start = busy->va_end;
        }

        if (vmap_end - vmap_start > 0) {
                free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
                if (!WARN_ON_ONCE(!free)) {
                        free->va_start = vmap_start;
                        free->va_end = vmap_end;

                        insert_vmap_area_augment(free, NULL,
                                &free_vmap_area_root,
                                        &free_vmap_area_list);
                }
        }
}

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

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

        for_each_possible_cpu(i) {
                struct vmap_block_queue *vbq;
                struct vfree_deferred *p;

                vbq = &per_cpu(vmap_block_queue, i);
                spin_lock_init(&vbq->lock);
                INIT_LIST_HEAD(&vbq->free);
                p = &per_cpu(vfree_deferred, i);
                init_llist_head(&p->list);
                INIT_WORK(&p->wq, free_work);
        }

        /* Import existing vmlist entries. */
        for (tmp = vmlist; tmp; tmp = tmp->next) {
                va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
                if (WARN_ON_ONCE(!va))
                        continue;

                va->va_start = (unsigned long)tmp->addr;
                va->va_end = va->va_start + tmp->size;
                va->vm = tmp;
                insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
        }

        /*
         * Now we can initialize a free vmap space.
         */
        vmap_init_free_space();
        vmap_initialized = true;
}

/**
 * unmap_kernel_range - unmap kernel VM area and flush cache and TLB
 * @addr: start of the VM area to unmap
 * @size: size of the VM area to unmap
 *
 * Similar to unmap_kernel_range_noflush() but flushes vcache before
 * the unmapping and tlb after.
 */
void unmap_kernel_range(unsigned long addr, unsigned long size)
{
        unsigned long end = addr + size;

        flush_cache_vunmap(addr, end);
        unmap_kernel_range_noflush(addr, size);
        flush_tlb_kernel_range(addr, end);
}

static inline void setup_vmalloc_vm_locked(struct vm_struct *vm,
        struct vmap_area *va, unsigned long flags, const void *caller)
{
        vm->flags = flags;
        vm->addr = (void *)va->va_start;
        vm->size = va->va_end - va->va_start;
        vm->caller = caller;
        va->vm = vm;
}

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

static void clear_vm_uninitialized_flag(struct vm_struct *vm)
{
        /*
         * Before removing VM_UNINITIALIZED,
         * we should make sure that vm has proper values.
         * Pair with smp_rmb() in show_numa_info().
         */
        smp_wmb();
        vm->flags &= ~VM_UNINITIALIZED;
}

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

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

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

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

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

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

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

        setup_vmalloc_vm(area, va, flags, caller);

        return area;
}

struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
                                       unsigned long start, unsigned long end,
                                       const void *caller)
{
        return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE,
                                  GFP_KERNEL, caller);
}

/**
 * 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.
 *
 * Return: 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, 1, flags, VMALLOC_START, VMALLOC_END,
                                  NUMA_NO_NODE, GFP_KERNEL,
                                  __builtin_return_address(0));
}

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

/**
 * 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.
 *
 * Return: the area descriptor on success or %NULL on failure.
 */
struct vm_struct *find_vm_area(const void *addr)
{
        struct vmap_area *va;

        va = find_vmap_area((unsigned long)addr);
        if (!va)
                return NULL;

        return va->vm;
}

/**
 * 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.
 *
 * Return: the area descriptor on success or %NULL on failure.
 */
struct vm_struct *remove_vm_area(const void *addr)
{
        struct vmap_area *va;

        might_sleep();

        spin_lock(&vmap_area_lock);
        va = __find_vmap_area((unsigned long)addr);
        if (va && va->vm) {
                struct vm_struct *vm = va->vm;

                va->vm = NULL;
                spin_unlock(&vmap_area_lock);

                kasan_free_shadow(vm);
                free_unmap_vmap_area(va);

                return vm;
        }

        spin_unlock(&vmap_area_lock);
        return NULL;
}

static inline void set_area_direct_map(const struct vm_struct *area,
                                       int (*set_direct_map)(struct page *page))
{
        int i;

        for (i = 0; i < area->nr_pages; i++)
                if (page_address(area->pages[i]))
                        set_direct_map(area->pages[i]);
}

/* Handle removing and resetting vm mappings related to the vm_struct. */
static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
{
        unsigned long start = ULONG_MAX, end = 0;
        int flush_reset = area->flags & VM_FLUSH_RESET_PERMS;
        int flush_dmap = 0;
        int i;

        remove_vm_area(area->addr);

        /* If this is not VM_FLUSH_RESET_PERMS memory, no need for the below. */
        if (!flush_reset)
                return;

        /*
         * If not deallocating pages, just do the flush of the VM area and
         * return.
         */
        if (!deallocate_pages) {
                vm_unmap_aliases();
                return;
        }

        /*
         * If execution gets here, flush the vm mapping and reset the direct
         * map. Find the start and end range of the direct mappings to make sure
         * the vm_unmap_aliases() flush includes the direct map.
         */
        for (i = 0; i < area->nr_pages; i++) {
                unsigned long addr = (unsigned long)page_address(area->pages[i]);
                if (addr) {
                        start = min(addr, start);
                        end = max(addr + PAGE_SIZE, end);
                        flush_dmap = 1;
                }
        }

        /*
         * Set direct map to something invalid so that it won't be cached if
         * there are any accesses after the TLB flush, then flush the TLB and
         * reset the direct map permissions to the default.
         */
        set_area_direct_map(area, set_direct_map_invalid_noflush);
        _vm_unmap_aliases(start, end, flush_dmap);
        set_area_direct_map(area, set_direct_map_default_noflush);
}

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(area->addr, get_vm_area_size(area));
        debug_check_no_obj_freed(area->addr, get_vm_area_size(area));

        kasan_poison_vmalloc(area->addr, get_vm_area_size(area));

        vm_remove_mappings(area, deallocate_pages);

        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);
                }
                atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);

                kvfree(area->pages);
        }

        kfree(area);
}

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
         * another 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);
}

static void __vfree(const void *addr)
{
        if (unlikely(in_interrupt()))
                __vfree_deferred(addr);
        else
                __vunmap(addr, 1);
}

/**
 * vfree - Release memory allocated by vmalloc()
 * @addr:  Memory base address
 *
 * Free the virtually continuous memory area starting at @addr, as obtained
 * from one of the vmalloc() family of APIs.  This will usually also free the
 * physical memory underlying the virtual allocation, but that memory is
 * reference counted, so it will not be freed until the last user goes away.
 *
 * If @addr is NULL, no operation is performed.
 *
 * Context:
 * May sleep if called *not* from interrupt context.
 * Must not be called in NMI context (strictly speaking, it could be
 * if we have CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG, but making the calling
 * conventions for vfree() arch-depenedent would be a really bad idea).
 */
void vfree(const void *addr)
{
        BUG_ON(in_nmi());

        kmemleak_free(addr);

        might_sleep_if(!in_interrupt());

        if (!addr)
                return;

        __vfree(addr);
}
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.
 * If @flags contains %VM_MAP_PUT_PAGES the ownership of the pages array itself
 * (which must be kmalloc or vmalloc memory) and one reference per pages in it
 * are transferred from the caller to vmap(), and will be freed / dropped when
 * vfree() is called on the return value.
 *
 * Return: the address of the area or %NULL on failure
 */
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_kernel_range((unsigned long)area->addr, size, pgprot_nx(prot),
                        pages) < 0) {
                vunmap(area->addr);
                return NULL;
        }

        if (flags & VM_MAP_PUT_PAGES)
                area->pages = pages;
        return area->addr;
}
EXPORT_SYMBOL(vmap);

#ifdef CONFIG_VMAP_PFN
struct vmap_pfn_data {
        unsigned long   *pfns;
        pgprot_t        prot;
        unsigned int    idx;
};

static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
{
        struct vmap_pfn_data *data = private;

        if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
                return -EINVAL;
        *pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
        return 0;
}

/**
 * vmap_pfn - map an array of PFNs into virtually contiguous space
 * @pfns: array of PFNs
 * @count: number of pages to map
 * @prot: page protection for the mapping
 *
 * Maps @count PFNs from @pfns into contiguous kernel virtual space and returns
 * the start address of the mapping.
 */
void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot)
{
        struct vmap_pfn_data data = { .pfns = pfns, .prot = pgprot_nx(prot) };
        struct vm_struct *area;

        area = get_vm_area_caller(count * PAGE_SIZE, VM_IOREMAP,
                        __builtin_return_address(0));
        if (!area)
                return NULL;
        if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
                        count * PAGE_SIZE, vmap_pfn_apply, &data)) {
                free_vm_area(area);
                return NULL;
        }
        return area->addr;
}
EXPORT_SYMBOL_GPL(vmap_pfn);
#endif /* CONFIG_VMAP_PFN */

static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
                                 pgprot_t prot, int node)
{
        const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
        unsigned int nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
        unsigned long array_size;
        unsigned int i;
        struct page **pages;

        array_size = (unsigned long)nr_pages * sizeof(struct page *);
        gfp_mask |= __GFP_NOWARN;
        if (!(gfp_mask & (GFP_DMA | GFP_DMA32)))
                gfp_mask |= __GFP_HIGHMEM;

        /* Please note that the recursion is strictly bounded. */
        if (array_size > PAGE_SIZE) {
                pages = __vmalloc_node(array_size, 1, nested_gfp, node,
                                        area->caller);
        } else {
                pages = kmalloc_node(array_size, nested_gfp, node);
        }

        if (!pages) {
                free_vm_area(area);
                return NULL;
        }

        area->pages = pages;
        area->nr_pages = nr_pages;

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

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

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

        if (map_kernel_range((unsigned long)area->addr, get_vm_area_size(area),
                        prot, pages) < 0)
                goto fail;

        return area->addr;

fail:
        warn_alloc(gfp_mask, NULL,
                          "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.
 *
 * Return: the address of the area or %NULL on failure
 */
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(real_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;

        /*
         * 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);

        kmemleak_vmalloc(area, size, gfp_mask);

        return addr;

fail:
        warn_alloc(gfp_mask, NULL,
                          "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
 * @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.
 *
 * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_RETRY_MAYFAIL
 * and __GFP_NOFAIL are not supported
 *
 * Any use of gfp flags outside of GFP_KERNEL should be consulted
 * with mm people.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *__vmalloc_node(unsigned long size, unsigned long align,
                            gfp_t gfp_mask, int node, const void *caller)
{
        return __vmalloc_node_range(size, align, VMALLOC_START, VMALLOC_END,
                                gfp_mask, PAGE_KERNEL, 0, node, caller);
}
/*
 * This is only for performance analysis of vmalloc and stress purpose.
 * It is required by vmalloc test module, therefore do not use it other
 * than that.
 */
#ifdef CONFIG_TEST_VMALLOC_MODULE
EXPORT_SYMBOL_GPL(__vmalloc_node);
#endif

void *__vmalloc(unsigned long size, gfp_t gfp_mask)
{
        return __vmalloc_node(size, 1, gfp_mask, NUMA_NO_NODE,
                                __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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vmalloc(unsigned long size)
{
        return __vmalloc_node(size, 1, GFP_KERNEL, NUMA_NO_NODE,
                                __builtin_return_address(0));
}
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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vzalloc(unsigned long size)
{
        return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_ZERO, NUMA_NO_NODE,
                                __builtin_return_address(0));
}
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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vmalloc_user(unsigned long size)
{
        return __vmalloc_node_range(size, SHMLBA,  VMALLOC_START, VMALLOC_END,
                                    GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL,
                                    VM_USERMAP, NUMA_NO_NODE,
                                    __builtin_return_address(0));
}
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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vmalloc_node(unsigned long size, int node)
{
        return __vmalloc_node(size, 1, GFP_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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vzalloc_node(unsigned long size, int node)
{
        return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_ZERO, node,
                                __builtin_return_address(0));
}
EXPORT_SYMBOL(vzalloc_node);

#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
/*
 * 64b systems should always have either DMA or DMA32 zones. For others
 * GFP_DMA32 should do the right thing and use the normal zone.
 */
#define GFP_VMALLOC32 GFP_DMA32 | 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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vmalloc_32(unsigned long size)
{
        return __vmalloc_node(size, 1, GFP_VMALLOC32, 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.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
void *vmalloc_32_user(unsigned long size)
{
        return __vmalloc_node_range(size, SHMLBA,  VMALLOC_START, VMALLOC_END,
                                    GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
                                    VM_USERMAP, NUMA_NO_NODE,
                                    __builtin_return_address(0));
}
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.
 *
 * 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 information, as /dev/kmem.
 *
 * Return: number of bytes for which addr and buf should be increased
 * (same number as @count) or %0 if [addr...addr+count) doesn't
 * include any intersection with valid vmalloc area
 */
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->vm)
                        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.
 *
 * 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 information, as /dev/kmem.
 *
 * Return: number of bytes for which addr and buf should be
 * increased (same number as @count) or %0 if [addr...addr+count)
 * doesn't include any intersection with valid vmalloc area
 */
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->vm)
                        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 | VM_DMA_COHERENT)))
                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);

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 rb_entry_safe(n, struct vmap_area, rb_node);
}

/**
 * pvm_find_va_enclose_addr - find the vmap_area @addr belongs to
 * @addr: target address
 *
 * Returns: vmap_area if it is found. If there is no such area
 *   the first highest(reverse order) vmap_area is returned
 *   i.e. va->va_start < addr && va->va_end < addr or NULL
 *   if there are no any areas before @addr.
 */
static struct vmap_area *
pvm_find_va_enclose_addr(unsigned long addr)
{
        struct vmap_area *va, *tmp;
        struct rb_node *n;

        n = free_vmap_area_root.rb_node;
        va = NULL;

        while (n) {
                tmp = rb_entry(n, struct vmap_area, rb_node);
                if (tmp->va_start <= addr) {
                        va = tmp;
                        if (tmp->va_end >= addr)
                                break;

                        n = n->rb_right;
                } else {
                        n = n->rb_left;
                }
        }

        return va;
}

/**
 * pvm_determine_end_from_reverse - find the highest aligned address
 * of free block below VMALLOC_END
 * @va:
 *   in - the VA we start the search(reverse order);
 *   out - the VA with the highest aligned end address.
 * @align: alignment for required highest address
 *
 * Returns: determined end address within vmap_area
 */
static unsigned long
pvm_determine_end_from_reverse(struct vmap_area **va, unsigned long align)
{
        unsigned long vmalloc_end = VMALLOC_END & ~(align - 1);
        unsigned long addr;

        if (likely(*va)) {
                list_for_each_entry_from_reverse((*va),
                                &free_vmap_area_list, list) {
                        addr = min((*va)->va_end & ~(align - 1), vmalloc_end);
                        if ((*va)->va_start < addr)
                                return addr;
                }
        }

        return 0;
}

/**
 * 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 free blocks from the end looking
 * for matching base. While scanning, if any of the areas do not fit the
 * base address is pulled down to fit the area. Scanning is repeated till
 * all the areas fit and then all necessary data structures 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, *va;
        struct vm_struct **vms;
        int area, area2, last_area, term_area;
        unsigned long base, start, size, end, last_end, orig_start, orig_end;
        bool purged = false;
        enum fit_type type;

        /* 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 = area + 1; area2 < nr_vms; area2++) {
                        unsigned long start2 = offsets[area2];
                        unsigned long end2 = start2 + sizes[area2];

                        BUG_ON(start2 < end && start < end2);
                }
        }
        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] = kmem_cache_zalloc(vmap_area_cachep, GFP_KERNEL);
                vms[area] = kzalloc(sizeof(struct vm_struct), GFP_KERNEL);
                if (!vas[area] || !vms[area])
                        goto err_free;
        }
retry:
        spin_lock(&free_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];

        va = pvm_find_va_enclose_addr(vmalloc_end);
        base = pvm_determine_end_from_reverse(&va, align) - end;

        while (true) {
                /*
                 * base might have underflowed, add last_end before
                 * comparing.
                 */
                if (base + last_end < vmalloc_start + last_end)
                        goto overflow;

                /*
                 * Fitting base has not been found.
                 */
                if (va == NULL)
                        goto overflow;

                /*
                 * If required width exceeds current VA block, move
                 * base downwards and then recheck.
                 */
                if (base + end > va->va_end) {
                        base = pvm_determine_end_from_reverse(&va, align) - end;
                        term_area = area;
                        continue;
                }

                /*
                 * If this VA does not fit, move base downwards and recheck.
                 */
                if (base + start < va->va_start) {
                        va = node_to_va(rb_prev(&va->rb_node));
                        base = pvm_determine_end_from_reverse(&va, 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];
                va = pvm_find_va_enclose_addr(base + end);
        }

        /* we've found a fitting base, insert all va's */
        for (area = 0; area < nr_vms; area++) {
                int ret;

                start = base + offsets[area];
                size = sizes[area];

                va = pvm_find_va_enclose_addr(start);
                if (WARN_ON_ONCE(va == NULL))
                        /* It is a BUG(), but trigger recovery instead. */
                        goto recovery;

                type = classify_va_fit_type(va, start, size);
                if (WARN_ON_ONCE(type == NOTHING_FIT))
                        /* It is a BUG(), but trigger recovery instead. */
                        goto recovery;

                ret = adjust_va_to_fit_type(va, start, size, type);
                if (unlikely(ret))
                        goto recovery;

                /* Allocated area. */
                va = vas[area];
                va->va_start = start;
                va->va_end = start + size;
        }

        spin_unlock(&free_vmap_area_lock);

        /* populate the kasan shadow space */
        for (area = 0; area < nr_vms; area++) {
                if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area]))
                        goto err_free_shadow;

                kasan_unpoison_vmalloc((void *)vas[area]->va_start,
                                       sizes[area]);
        }

        /* insert all vm's */
        spin_lock(&vmap_area_lock);
        for (area = 0; area < nr_vms; area++) {
                insert_vmap_area(vas[area], &vmap_area_root, &vmap_area_list);

                setup_vmalloc_vm_locked(vms[area], vas[area], VM_ALLOC,
                                 pcpu_get_vm_areas);
        }
        spin_unlock(&vmap_area_lock);

        kfree(vas);
        return vms;

recovery:
        /*
         * Remove previously allocated areas. There is no
         * need in removing these areas from the busy tree,
         * because they are inserted only on the final step
         * and when pcpu_get_vm_areas() is success.
         */
        while (area--) {
                orig_start = vas[area]->va_start;
                orig_end = vas[area]->va_end;
                va = merge_or_add_vmap_area_augment(vas[area], &free_vmap_area_root,
                                &free_vmap_area_list);
                if (va)
                        kasan_release_vmalloc(orig_start, orig_end,
                                va->va_start, va->va_end);
                vas[area] = NULL;
        }

overflow:
        spin_unlock(&free_vmap_area_lock);
        if (!purged) {
                purge_vmap_area_lazy();
                purged = true;

                /* Before "retry", check if we recover. */
                for (area = 0; area < nr_vms; area++) {
                        if (vas[area])
                                continue;

                        vas[area] = kmem_cache_zalloc(
                                vmap_area_cachep, GFP_KERNEL);
                        if (!vas[area])
                                goto err_free;
                }

                goto retry;
        }

err_free:
        for (area = 0; area < nr_vms; area++) {
                if (vas[area])
                        kmem_cache_free(vmap_area_cachep, vas[area]);

                kfree(vms[area]);
        }
err_free2:
        kfree(vas);
        kfree(vms);
        return NULL;

err_free_shadow:
        spin_lock(&free_vmap_area_lock);
        /*
         * We release all the vmalloc shadows, even the ones for regions that
         * hadn't been successfully added. This relies on kasan_release_vmalloc
         * being able to tolerate this case.
         */
        for (area = 0; area < nr_vms; area++) {
                orig_start = vas[area]->va_start;
                orig_end = vas[area]->va_end;
                va = merge_or_add_vmap_area_augment(vas[area], &free_vmap_area_root,
                                &free_vmap_area_list);
                if (va)
                        kasan_release_vmalloc(orig_start, orig_end,
                                va->va_start, va->va_end);
                vas[area] = NULL;
                kfree(vms[area]);
        }
        spin_unlock(&free_vmap_area_lock);
        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_purge_lock)
        __acquires(&vmap_area_lock)
{
        mutex_lock(&vmap_purge_lock);
        spin_lock(&vmap_area_lock);

        return seq_list_start(&vmap_area_list, *pos);
}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
        return seq_list_next(p, &vmap_area_list, pos);
}

static void s_stop(struct seq_file *m, void *p)
        __releases(&vmap_area_lock)
        __releases(&vmap_purge_lock)
{
        spin_unlock(&vmap_area_lock);
        mutex_unlock(&vmap_purge_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 void show_purge_info(struct seq_file *m)
{
        struct vmap_area *va;

        spin_lock(&purge_vmap_area_lock);
        list_for_each_entry(va, &purge_vmap_area_list, list) {
                seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n",
                        (void *)va->va_start, (void *)va->va_end,
                        va->va_end - va->va_start);
        }
        spin_unlock(&purge_vmap_area_lock);
}

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

        va = list_entry(p, struct vmap_area, list);

        /*
         * s_show can encounter race with remove_vm_area, !vm on behalf
         * of vmap area is being tear down or vm_map_ram allocation.
         */
        if (!va->vm) {
                seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
                        (void *)va->va_start, (void *)va->va_end,
                        va->va_end - va->va_start);

                return 0;
        }

        v = va->vm;

        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=%pa", &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 (v->flags & VM_DMA_COHERENT)
                seq_puts(m, " dma-coherent");

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

        show_numa_info(m, v);
        seq_putc(m, '\n');

        /*
         * As a final step, dump "unpurged" areas.
         */
        if (list_is_last(&va->list, &vmap_area_list))
                show_purge_info(m);

        return 0;
}

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

static int __init proc_vmalloc_init(void)
{
        if (IS_ENABLED(CONFIG_NUMA))
                proc_create_seq_private("vmallocinfo", 0400, NULL,
                                &vmalloc_op,
                                nr_node_ids * sizeof(unsigned int), NULL);
        else
                proc_create_seq("vmallocinfo", 0400, NULL, &vmalloc_op);
        return 0;
}
module_init(proc_vmalloc_init);

#endif