/*
 * mm/mmap.c
 *
 * Written by obz.
 *
 * Address space accounting code        <alan@redhat.com>
 */

#include <linux/slab.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/security.h>

#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>

extern void unmap_page_range(mmu_gather_t *,struct vm_area_struct *vma, unsigned long address, unsigned long size);
extern void clear_page_tables(mmu_gather_t *tlb, unsigned long first, int nr);

/*
 * WARNING: the debugging will use recursive algorithms so never enable this
 * unless you know what you are doing.
 */
#undef DEBUG_MM_RB

/* description of effects of mapping type and prot in current implementation.
 * this is due to the limited x86 page protection hardware.  The expected
 * behavior is in parens:
 *
 * map_type     prot
 *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
 * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 *              
 * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 *
 */
pgprot_t protection_map[16] = {
        __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
        __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
};

int sysctl_overcommit_memory = 0;       /* default is heuristic overcommit */
int sysctl_overcommit_ratio = 50;       /* default is 50% */
atomic_t vm_committed_space = ATOMIC_INIT(0);

inline void vm_unacct_memory(long pages)
{       
        atomic_sub(pages, &vm_committed_space);
}

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 1 means there is enough memory for the allocation to
 * succeed and 0 implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 */
int vm_enough_memory(long pages)
{
        unsigned long free, allowed;
        struct sysinfo i;

        atomic_add(pages, &vm_committed_space);

        /*
         * Sometimes we want to use more memory than we have
         */
        if (sysctl_overcommit_memory == 1)
                return 1;

        if (sysctl_overcommit_memory == 0) {
                free = get_page_cache_size();
                free += nr_free_pages();
                free += nr_swap_pages;

                /*
                 * This double-counts: the nrpages are both in the
                 * page-cache and in the swapper space. At the same time,
                 * this compensates for the swap-space over-allocation
                 * (ie "nr_swap_pages" being too small).
                 */
                free += swapper_space.nrpages;

                /*
                 * The code below doesn't account for free space in the
                 * inode and dentry slab cache, slab cache fragmentation,
                 * inodes and dentries which will become freeable under
                 * VM load, etc. Lets just hope all these (complex)
                 * factors balance out...
                 */
                free += (dentry_stat.nr_unused * sizeof(struct dentry)) >>
                        PAGE_SHIFT;
                free += (inodes_stat.nr_unused * sizeof(struct inode)) >>
                        PAGE_SHIFT;

                if (free > pages)
                        return 1;
                vm_unacct_memory(pages);
                return 0;
        }

        /*
         * FIXME: need to add arch hooks to get the bits we need
         * without this higher overhead crap
         */
        si_meminfo(&i);
        allowed = i.totalram * sysctl_overcommit_ratio / 100;
        allowed += total_swap_pages;

        if (atomic_read(&vm_committed_space) < allowed)
                return 1;

        vm_unacct_memory(pages);

        return 0;
}

/* Remove one vm structure from the inode's i_mapping address space. */
static inline void remove_shared_vm_struct(struct vm_area_struct *vma)
{
        struct file *file = vma->vm_file;

        if (file) {
                struct inode *inode = file->f_dentry->d_inode;

                spin_lock(&inode->i_mapping->i_shared_lock);
                if (vma->vm_flags & VM_DENYWRITE)
                        atomic_inc(&inode->i_writecount);
                list_del_init(&vma->shared);
                spin_unlock(&inode->i_mapping->i_shared_lock);
        }
}

/*
 *  sys_brk() for the most part doesn't need the global kernel
 *  lock, except when an application is doing something nasty
 *  like trying to un-brk an area that has already been mapped
 *  to a regular file.  in this case, the unmapping will need
 *  to invoke file system routines that need the global lock.
 */
asmlinkage unsigned long sys_brk(unsigned long brk)
{
        unsigned long rlim, retval;
        unsigned long newbrk, oldbrk;
        struct mm_struct *mm = current->mm;

        down_write(&mm->mmap_sem);

        if (brk < mm->end_code)
                goto out;
        newbrk = PAGE_ALIGN(brk);
        oldbrk = PAGE_ALIGN(mm->brk);
        if (oldbrk == newbrk)
                goto set_brk;

        /* Always allow shrinking brk. */
        if (brk <= mm->brk) {
                if (!do_munmap(mm, newbrk, oldbrk-newbrk))
                        goto set_brk;
                goto out;
        }

        /* Check against rlimit.. */
        rlim = current->rlim[RLIMIT_DATA].rlim_cur;
        if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
                goto out;

        /* Check against existing mmap mappings. */
        if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
                goto out;

        /* Ok, looks good - let it rip. */
        if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
                goto out;
set_brk:
        mm->brk = brk;
out:
        retval = mm->brk;
        up_write(&mm->mmap_sem);
        return retval;
}

/* Combine the mmap "prot" and "flags" argument into one "vm_flags" used
 * internally. Essentially, translate the "PROT_xxx" and "MAP_xxx" bits
 * into "VM_xxx".
 */
static inline unsigned long calc_vm_flags(unsigned long prot, unsigned long flags)
{
#define _trans(x,bit1,bit2) \
((bit1==bit2)?(x&bit1):(x&bit1)?bit2:0)

        unsigned long prot_bits, flag_bits;
        prot_bits =
                _trans(prot, PROT_READ, VM_READ) |
                _trans(prot, PROT_WRITE, VM_WRITE) |
                _trans(prot, PROT_EXEC, VM_EXEC);
        flag_bits =
                _trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN) |
                _trans(flags, MAP_DENYWRITE, VM_DENYWRITE) |
                _trans(flags, MAP_EXECUTABLE, VM_EXECUTABLE);
        return prot_bits | flag_bits;
#undef _trans
}

#ifdef DEBUG_MM_RB
static int browse_rb(struct rb_node * rb_node) {
        int i = 0;
        if (rb_node) {
                i++;
                i += browse_rb(rb_node->rb_left);
                i += browse_rb(rb_node->rb_right);
        }
        return i;
}

static void validate_mm(struct mm_struct * mm) {
        int bug = 0;
        int i = 0;
        struct vm_area_struct * tmp = mm->mmap;
        while (tmp) {
                tmp = tmp->vm_next;
                i++;
        }
        if (i != mm->map_count)
                printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
        i = browse_rb(mm->mm_rb.rb_node);
        if (i != mm->map_count)
                printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
        if (bug)
                BUG();
}
#else
#define validate_mm(mm) do { } while (0)
#endif

static struct vm_area_struct * find_vma_prepare(struct mm_struct * mm, unsigned long addr,
                                                struct vm_area_struct ** pprev,
                                                struct rb_node *** rb_link,
                                                struct rb_node ** rb_parent)
{
        struct vm_area_struct * vma;
        struct rb_node ** __rb_link, * __rb_parent, * rb_prev;

        __rb_link = &mm->mm_rb.rb_node;
        rb_prev = __rb_parent = NULL;
        vma = NULL;

        while (*__rb_link) {
                struct vm_area_struct *vma_tmp;

                __rb_parent = *__rb_link;
                vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);

                if (vma_tmp->vm_end > addr) {
                        vma = vma_tmp;
                        if (vma_tmp->vm_start <= addr)
                                return vma;
                        __rb_link = &__rb_parent->rb_left;
                } else {
                        rb_prev = __rb_parent;
                        __rb_link = &__rb_parent->rb_right;
                }
        }

        *pprev = NULL;
        if (rb_prev)
                *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
        *rb_link = __rb_link;
        *rb_parent = __rb_parent;
        return vma;
}

static inline void __vma_link_list(struct mm_struct * mm, struct vm_area_struct * vma,
                                   struct vm_area_struct * prev, struct rb_node * rb_parent)
{
        if (prev) {
                vma->vm_next = prev->vm_next;
                prev->vm_next = vma;
        } else {
                mm->mmap = vma;
                if (rb_parent)
                        vma->vm_next = rb_entry(rb_parent, struct vm_area_struct, vm_rb);
                else
                        vma->vm_next = NULL;
        }
}

static inline void __vma_link_rb(struct mm_struct * mm, struct vm_area_struct * vma,
                                 struct rb_node ** rb_link, struct rb_node * rb_parent)
{
        rb_link_node(&vma->vm_rb, rb_parent, rb_link);
        rb_insert_color(&vma->vm_rb, &mm->mm_rb);
}

static inline void __vma_link_file(struct vm_area_struct * vma)
{
        struct file * file;

        file = vma->vm_file;
        if (file) {
                struct inode * inode = file->f_dentry->d_inode;
                struct address_space *mapping = inode->i_mapping;

                if (vma->vm_flags & VM_DENYWRITE)
                        atomic_dec(&inode->i_writecount);

                if (vma->vm_flags & VM_SHARED)
                        list_add_tail(&vma->shared, &mapping->i_mmap_shared);
                else
                        list_add_tail(&vma->shared, &mapping->i_mmap);
        }
}

static void __vma_link(struct mm_struct * mm, struct vm_area_struct * vma,  struct vm_area_struct * prev,
                       struct rb_node ** rb_link, struct rb_node * rb_parent)
{
        __vma_link_list(mm, vma, prev, rb_parent);
        __vma_link_rb(mm, vma, rb_link, rb_parent);
        __vma_link_file(vma);
}

static inline void vma_link(struct mm_struct * mm, struct vm_area_struct * vma, struct vm_area_struct * prev,
                            struct rb_node ** rb_link, struct rb_node * rb_parent)
{
        struct address_space *mapping = NULL;

        if (vma->vm_file)
                mapping = vma->vm_file->f_dentry->d_inode->i_mapping;

        if (mapping)
                spin_lock(&mapping->i_shared_lock);
        spin_lock(&mm->page_table_lock);
        __vma_link(mm, vma, prev, rb_link, rb_parent);
        spin_unlock(&mm->page_table_lock);
        if (mapping)
                spin_unlock(&mapping->i_shared_lock);

        mm->map_count++;
        validate_mm(mm);
}

static int vma_merge(struct mm_struct * mm, struct vm_area_struct * prev,
                     struct rb_node * rb_parent, unsigned long addr, 
                     unsigned long end, unsigned long vm_flags)
{
        spinlock_t * lock = &mm->page_table_lock;
        if (!prev) {
                prev = rb_entry(rb_parent, struct vm_area_struct, vm_rb);
                goto merge_next;
        }
        if (prev->vm_end == addr && can_vma_merge(prev, vm_flags)) {
                struct vm_area_struct * next;

                spin_lock(lock);
                prev->vm_end = end;
                next = prev->vm_next;
                if (next && prev->vm_end == next->vm_start && can_vma_merge(next, vm_flags)) {
                        prev->vm_end = next->vm_end;
                        __vma_unlink(mm, next, prev);
                        spin_unlock(lock);

                        mm->map_count--;
                        kmem_cache_free(vm_area_cachep, next);
                        return 1;
                }
                spin_unlock(lock);
                return 1;
        }

        prev = prev->vm_next;
        if (prev) {
 merge_next:
                if (!can_vma_merge(prev, vm_flags))
                        return 0;
                if (end == prev->vm_start) {
                        spin_lock(lock);
                        prev->vm_start = addr;
                        spin_unlock(lock);
                        return 1;
                }
        }

        return 0;
}

unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
                        unsigned long len, unsigned long prot,
                        unsigned long flags, unsigned long pgoff)
{
        struct mm_struct * mm = current->mm;
        struct vm_area_struct * vma, * prev;
        struct inode *inode = NULL;
        unsigned int vm_flags;
        int correct_wcount = 0;
        int error;
        struct rb_node ** rb_link, * rb_parent;
        unsigned long charged = 0;

        if (file && (!file->f_op || !file->f_op->mmap))
                return -ENODEV;

        if (!len)
                return addr;

        if (len > TASK_SIZE)
                return -EINVAL;

        len = PAGE_ALIGN(len);

        /* offset overflow? */
        if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
                return -EINVAL;

        /* Too many mappings? */
        if (mm->map_count > MAX_MAP_COUNT)
                return -ENOMEM;

        /* Obtain the address to map to. we verify (or select) it and ensure
         * that it represents a valid section of the address space.
         */
        addr = get_unmapped_area(file, addr, len, pgoff, flags);
        if (addr & ~PAGE_MASK)
                return addr;

        /* Do simple checking here so the lower-level routines won't have
         * to. we assume access permissions have been handled by the open
         * of the memory object, so we don't do any here.
         */
        vm_flags = calc_vm_flags(prot,flags) | mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;

        if (flags & MAP_LOCKED) {
                if (!capable(CAP_IPC_LOCK))
                        return -EPERM;
                vm_flags |= VM_LOCKED;
        }
        /* mlock MCL_FUTURE? */
        if (vm_flags & VM_LOCKED) {
                unsigned long locked = mm->locked_vm << PAGE_SHIFT;
                locked += len;
                if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
                        return -EAGAIN;
        }

        if (file) {
                inode = file->f_dentry->d_inode;
                switch (flags & MAP_TYPE) {
                case MAP_SHARED:
                        if ((prot & PROT_WRITE) && !(file->f_mode & FMODE_WRITE))
                                return -EACCES;

                        /* Make sure we don't allow writing to an append-only file.. */
                        if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
                                return -EACCES;

                        /* make sure there are no mandatory locks on the file. */
                        if (locks_verify_locked(inode))
                                return -EAGAIN;

                        vm_flags |= VM_SHARED | VM_MAYSHARE;
                        if (!(file->f_mode & FMODE_WRITE))
                                vm_flags &= ~(VM_MAYWRITE | VM_SHARED);

                        /* fall through */
                case MAP_PRIVATE:
                        if (!(file->f_mode & FMODE_READ))
                                return -EACCES;
                        break;

                default:
                        return -EINVAL;
                }
        } else {
                vm_flags |= VM_SHARED | VM_MAYSHARE;
                switch (flags & MAP_TYPE) {
                default:
                        return -EINVAL;
                case MAP_PRIVATE:
                        vm_flags &= ~(VM_SHARED | VM_MAYSHARE);
                        /* fall through */
                case MAP_SHARED:
                        break;
                }
        }

        error = security_ops->file_mmap(file, prot, flags);
        if (error)
                return error;
                
        /* Clear old maps */
        error = -ENOMEM;
munmap_back:
        vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
        if (vma && vma->vm_start < addr + len) {
                if (do_munmap(mm, addr, len))
                        return -ENOMEM;
                goto munmap_back;
        }

        /* Check against address space limit. */
        if ((mm->total_vm << PAGE_SHIFT) + len
            > current->rlim[RLIMIT_AS].rlim_cur)
                return -ENOMEM;

        if (!(flags & MAP_NORESERVE) || sysctl_overcommit_memory > 1) {
                if (vm_flags & VM_SHARED) {
                        /* Check memory availability in shmem_file_setup? */
                        vm_flags |= VM_ACCOUNT;
                } else if (vm_flags & VM_WRITE) {
                        /* Private writable mapping: check memory availability */
                        charged = len >> PAGE_SHIFT;
                        if (!vm_enough_memory(charged))
                                return -ENOMEM;
                        vm_flags |= VM_ACCOUNT;
                }
        }

        /* Can we just expand an old anonymous mapping? */
        if (!file && !(vm_flags & VM_SHARED) && rb_parent)
                if (vma_merge(mm, prev, rb_parent, addr, addr + len, vm_flags))
                        goto out;

        /* Determine the object being mapped and call the appropriate
         * specific mapper. the address has already been validated, but
         * not unmapped, but the maps are removed from the list.
         */
        vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        error = -ENOMEM;
        if (!vma)
                goto unacct_error;

        vma->vm_mm = mm;
        vma->vm_start = addr;
        vma->vm_end = addr + len;
        vma->vm_flags = vm_flags;
        vma->vm_page_prot = protection_map[vm_flags & 0x0f];
        vma->vm_ops = NULL;
        vma->vm_pgoff = pgoff;
        vma->vm_file = NULL;
        vma->vm_private_data = NULL;
        vma->vm_raend = 0;

        if (file) {
                error = -EINVAL;
                if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
                        goto free_vma;
                if (vm_flags & VM_DENYWRITE) {
                        error = deny_write_access(file);
                        if (error)
                                goto free_vma;
                        correct_wcount = 1;
                }
                vma->vm_file = file;
                get_file(file);
                error = file->f_op->mmap(file, vma);
                if (error)
                        goto unmap_and_free_vma;
        } else if (vm_flags & VM_SHARED) {
                error = shmem_zero_setup(vma);
                if (error)
                        goto free_vma;
        }

        /* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform
         * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)
         * that memory reservation must be checked; but that reservation
         * belongs to shared memory object, not to vma: so now clear it.
         */
        if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))
                vma->vm_flags &= ~VM_ACCOUNT;

        /* Can addr have changed??
         *
         * Answer: Yes, several device drivers can do it in their
         *         f_op->mmap method. -DaveM
         */
        addr = vma->vm_start;

        vma_link(mm, vma, prev, rb_link, rb_parent);
        if (correct_wcount)
                atomic_inc(&inode->i_writecount);

out:    
        mm->total_vm += len >> PAGE_SHIFT;
        if (vm_flags & VM_LOCKED) {
                mm->locked_vm += len >> PAGE_SHIFT;
                make_pages_present(addr, addr + len);
        }
        return addr;

unmap_and_free_vma:
        if (correct_wcount)
                atomic_inc(&inode->i_writecount);
        vma->vm_file = NULL;
        fput(file);

        /* Undo any partial mapping done by a device driver. */
        zap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start);
free_vma:
        kmem_cache_free(vm_area_cachep, vma);
unacct_error:
        if (charged)
                vm_unacct_memory(charged);
        return error;
}

/* Get an address range which is currently unmapped.
 * For shmat() with addr=0.
 *
 * Ugly calling convention alert:
 * Return value with the low bits set means error value,
 * ie
 *      if (ret & ~PAGE_MASK)
 *              error = ret;
 *
 * This function "knows" that -ENOMEM has the bits set.
 */
#ifndef HAVE_ARCH_UNMAPPED_AREA
static inline unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
        struct vm_area_struct *vma;

        if (len > TASK_SIZE)
                return -ENOMEM;

        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(current->mm, addr);
                if (TASK_SIZE - len >= addr &&
                    (!vma || addr + len <= vma->vm_start))
                        return addr;
        }
        addr = PAGE_ALIGN(TASK_UNMAPPED_BASE);

        for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
                /* At this point:  (!vma || addr < vma->vm_end). */
                if (TASK_SIZE - len < addr)
                        return -ENOMEM;
                if (!vma || addr + len <= vma->vm_start)
                        return addr;
                addr = vma->vm_end;
        }
}
#else
extern unsigned long arch_get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
#endif  

unsigned long get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
        if (flags & MAP_FIXED) {
                if (addr > TASK_SIZE - len)
                        return -ENOMEM;
                if (addr & ~PAGE_MASK)
                        return -EINVAL;
                return addr;
        }

        if (file && file->f_op && file->f_op->get_unmapped_area)
                return file->f_op->get_unmapped_area(file, addr, len, pgoff, flags);

        return arch_get_unmapped_area(file, addr, len, pgoff, flags);
}

/* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr)
{
        struct vm_area_struct *vma = NULL;

        if (mm) {
                /* Check the cache first. */
                /* (Cache hit rate is typically around 35%.) */
                vma = mm->mmap_cache;
                if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
                        struct rb_node * rb_node;

                        rb_node = mm->mm_rb.rb_node;
                        vma = NULL;

                        while (rb_node) {
                                struct vm_area_struct * vma_tmp;

                                vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);

                                if (vma_tmp->vm_end > addr) {
                                        vma = vma_tmp;
                                        if (vma_tmp->vm_start <= addr)
                                                break;
                                        rb_node = rb_node->rb_left;
                                } else
                                        rb_node = rb_node->rb_right;
                        }
                        if (vma)
                                mm->mmap_cache = vma;
                }
        }
        return vma;
}

/* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
                                      struct vm_area_struct **pprev)
{
        struct vm_area_struct *vma = NULL, *prev = NULL;
        struct rb_node * rb_node;
        if (!mm)
                goto out;

        /* Guard against addr being lower than the first VMA */
        vma = mm->mmap;

        /* Go through the RB tree quickly. */
        rb_node = mm->mm_rb.rb_node;

        while (rb_node) {
                struct vm_area_struct *vma_tmp;
                vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);

                if (addr < vma_tmp->vm_end) {
                        rb_node = rb_node->rb_left;
                } else {
                        prev = vma_tmp;
                        if (!prev->vm_next || (addr < prev->vm_next->vm_end))
                                break;
                        rb_node = rb_node->rb_right;
                }
        }

 out:
        *pprev = prev;
        return prev ? prev->vm_next : vma;
}

#ifdef ARCH_STACK_GROWSUP
/*
 * vma is the first one with address > vma->vm_end.  Have to extend vma.
 */
int expand_stack(struct vm_area_struct * vma, unsigned long address)
{
        unsigned long grow;

        if (!(vma->vm_flags & VM_GROWSUP))
                return -EFAULT;

        /*
         * vma->vm_start/vm_end cannot change under us because the caller
         * is required to hold the mmap_sem in read mode. We need to get
         * the spinlock only before relocating the vma range ourself.
         */
        address += 4 + PAGE_SIZE - 1;
        address &= PAGE_MASK;
        spin_lock(&vma->vm_mm->page_table_lock);
        grow = (address - vma->vm_end) >> PAGE_SHIFT;

        /* Overcommit.. */
        if (!vm_enough_memory(grow)) {
                spin_unlock(&vma->vm_mm->page_table_lock);
                return -ENOMEM;
        }
        
        if (address - vma->vm_start > current->rlim[RLIMIT_STACK].rlim_cur ||
                        ((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) >
                        current->rlim[RLIMIT_AS].rlim_cur) {
                spin_unlock(&vma->vm_mm->page_table_lock);
                vm_unacct_memory(grow);
                return -ENOMEM;
        }
        vma->vm_end = address;
        vma->vm_mm->total_vm += grow;
        if (vma->vm_flags & VM_LOCKED)
                vma->vm_mm->locked_vm += grow;
        spin_unlock(&vma->vm_mm->page_table_lock);
        return 0;
}

struct vm_area_struct * find_extend_vma(struct mm_struct * mm, unsigned long addr)
{
        struct vm_area_struct *vma, *prev;

        addr &= PAGE_MASK;
        vma = find_vma_prev(mm, addr, &prev);
        if (vma && (vma->vm_start <= addr))
                return vma;
        if (!prev || expand_stack(prev, addr))
                return NULL;
        if (prev->vm_flags & VM_LOCKED) {
                make_pages_present(addr, prev->vm_end);
        }
        return prev;
}
#else
/*
 * vma is the first one with address < vma->vm_start.  Have to extend vma.
 */
int expand_stack(struct vm_area_struct * vma, unsigned long address)
{
        unsigned long grow;

        /*
         * vma->vm_start/vm_end cannot change under us because the caller
         * is required to hold the mmap_sem in read mode. We need to get
         * the spinlock only before relocating the vma range ourself.
         */
        address &= PAGE_MASK;
        spin_lock(&vma->vm_mm->page_table_lock);
        grow = (vma->vm_start - address) >> PAGE_SHIFT;

        /* Overcommit.. */
        if (!vm_enough_memory(grow)) {
                spin_unlock(&vma->vm_mm->page_table_lock);
                return -ENOMEM;
        }
        
        if (vma->vm_end - address > current->rlim[RLIMIT_STACK].rlim_cur ||
                        ((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) >
                        current->rlim[RLIMIT_AS].rlim_cur) {
                spin_unlock(&vma->vm_mm->page_table_lock);
                vm_unacct_memory(grow);
                return -ENOMEM;
        }
        vma->vm_start = address;
        vma->vm_pgoff -= grow;
        vma->vm_mm->total_vm += grow;
        if (vma->vm_flags & VM_LOCKED)
                vma->vm_mm->locked_vm += grow;
        spin_unlock(&vma->vm_mm->page_table_lock);
        return 0;
}

struct vm_area_struct * find_extend_vma(struct mm_struct * mm, unsigned long addr)
{
        struct vm_area_struct * vma;
        unsigned long start;

        addr &= PAGE_MASK;
        vma = find_vma(mm,addr);
        if (!vma)
                return NULL;
        if (vma->vm_start <= addr)
                return vma;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                return NULL;
        start = vma->vm_start;
        if (expand_stack(vma, addr))
                return NULL;
        if (vma->vm_flags & VM_LOCKED) {
                make_pages_present(addr, start);
        }
        return vma;
}
#endif

/*
 * Try to free as many page directory entries as we can,
 * without having to work very hard at actually scanning
 * the page tables themselves.
 *
 * Right now we try to free page tables if we have a nice
 * PGDIR-aligned area that got free'd up. We could be more
 * granular if we want to, but this is fast and simple,
 * and covers the bad cases.
 *
 * "prev", if it exists, points to a vma before the one
 * we just free'd - but there's no telling how much before.
 */
static void free_pgtables(mmu_gather_t *tlb, struct vm_area_struct *prev,
        unsigned long start, unsigned long end)
{
        unsigned long first = start & PGDIR_MASK;
        unsigned long last = end + PGDIR_SIZE - 1;
        unsigned long start_index, end_index;
        struct mm_struct *mm = tlb->mm;

        if (!prev) {
                prev = mm->mmap;
                if (!prev)
                        goto no_mmaps;
                if (prev->vm_end > start) {
                        if (last > prev->vm_start)
                                last = prev->vm_start;
                        goto no_mmaps;
                }
        }
        for (;;) {
                struct vm_area_struct *next = prev->vm_next;

                if (next) {
                        if (next->vm_start < start) {
                                prev = next;
                                continue;
                        }
                        if (last > next->vm_start)
                                last = next->vm_start;
                }
                if (prev->vm_end > first)
                        first = prev->vm_end + PGDIR_SIZE - 1;
                break;
        }
no_mmaps:
        if (last < first)       /* needed for arches with discontiguous pgd indices */
                return;
        /*
         * If the PGD bits are not consecutive in the virtual address, the
         * old method of shifting the VA >> by PGDIR_SHIFT doesn't work.
         */
        start_index = pgd_index(first);
        if (start_index < FIRST_USER_PGD_NR)
                start_index = FIRST_USER_PGD_NR;
        end_index = pgd_index(last);
        if (end_index > start_index) {
                clear_page_tables(tlb, start_index, end_index - start_index);
                flush_tlb_pgtables(mm, first & PGDIR_MASK, last & PGDIR_MASK);
        }
}

/* Normal function to fix up a mapping
 * This function is the default for when an area has no specific
 * function.  This may be used as part of a more specific routine.
 *
 * By the time this function is called, the area struct has been
 * removed from the process mapping list.
 */
static void unmap_vma(struct mm_struct *mm, struct vm_area_struct *area)
{
        size_t len = area->vm_end - area->vm_start;

        area->vm_mm->total_vm -= len >> PAGE_SHIFT;
        if (area->vm_flags & VM_LOCKED)
                area->vm_mm->locked_vm -= len >> PAGE_SHIFT;

        remove_shared_vm_struct(area);

        if (area->vm_ops && area->vm_ops->close)
                area->vm_ops->close(area);
        if (area->vm_file)
                fput(area->vm_file);
        kmem_cache_free(vm_area_cachep, area);
}

/*
 * Update the VMA and inode share lists.
 *
 * Ok - we have the memory areas we should free on the 'free' list,
 * so release them, and do the vma updates.
 */
static void unmap_vma_list(struct mm_struct *mm,
        struct vm_area_struct *mpnt)
{
        do {
                struct vm_area_struct *next = mpnt->vm_next;
                unmap_vma(mm, mpnt);
                mpnt = next;
        } while (mpnt != NULL);
        validate_mm(mm);
}

/*
 * Get rid of page table information in the indicated region.
 *
 * Called with the page table lock held.
 */
static void unmap_region(struct mm_struct *mm,
        struct vm_area_struct *mpnt,
        struct vm_area_struct *prev,
        unsigned long start,
        unsigned long end)
{
        mmu_gather_t *tlb;

        tlb = tlb_gather_mmu(mm, 0);

        do {
                unsigned long from, to, len;

                from = start < mpnt->vm_start ? mpnt->vm_start : start;
                to = end > mpnt->vm_end ? mpnt->vm_end : end;

                unmap_page_range(tlb, mpnt, from, to);

                if (mpnt->vm_flags & VM_ACCOUNT) {
                        len = to - from;
                        vm_unacct_memory(len >> PAGE_SHIFT);
                }
        } while ((mpnt = mpnt->vm_next) != NULL);

        free_pgtables(tlb, prev, start, end);
        tlb_finish_mmu(tlb, start, end);

}

/*
 * Create a list of vma's touched by the unmap,
 * removing them from the VM lists as we go..
 *
 * Called with the page_table_lock held.
 */
static struct vm_area_struct *touched_by_munmap(struct mm_struct *mm,
        struct vm_area_struct *mpnt,
        struct vm_area_struct *prev,
        unsigned long end)
{
        struct vm_area_struct **npp, *touched;

        npp = (prev ? &prev->vm_next : &mm->mmap);

        touched = NULL;
        do {
                struct vm_area_struct *next = mpnt->vm_next;
                if (!(is_vm_hugetlb_page(mpnt))) {
                        mpnt->vm_next = touched;
                        touched = mpnt;
                        rb_erase(&mpnt->vm_rb, &mm->mm_rb);
                        mm->map_count--;
                }
                else
                        free_hugepages(mpnt);
                mpnt = next;
        } while (mpnt && mpnt->vm_start < end);
        *npp = mpnt;
        mm->mmap_cache = NULL;  /* Kill the cache. */
        return touched;
}

/*
 * Split a vma into two pieces at address 'addr', a new vma is allocated
 * either for the first part or the the tail.
 */
int split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
              unsigned long addr, int new_below)
{
        struct vm_area_struct *new;

        if (mm->map_count >= MAX_MAP_COUNT)
                return -ENOMEM;

        new = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!new)
                return -ENOMEM;

        /* most fields are the same, copy all, and then fixup */
        *new = *vma;

        if (new_below) {
                new->vm_end = addr;
                vma->vm_start = addr;
                vma->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
        } else {
                vma->vm_end = addr;
                new->vm_start = addr;
                new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
        }

        new->vm_raend = 0;

        if (new->vm_file)
                get_file(new->vm_file);

        if (new->vm_ops && new->vm_ops->open)
                new->vm_ops->open(new);

        insert_vm_struct(mm, new);
        return 0;
}

/* Munmap is split into 2 main parts -- this part which finds
 * what needs doing, and the areas themselves, which do the
 * work.  This now handles partial unmappings.
 * Jeremy Fitzhardinge <jeremy@goop.org>
 */
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
{
        unsigned long end;
        struct vm_area_struct *mpnt, *prev, *last;

        if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
                return -EINVAL;

        if ((len = PAGE_ALIGN(len)) == 0)
                return -EINVAL;

        /* Find the first overlapping VMA */
        mpnt = find_vma_prev(mm, start, &prev);
        if (!mpnt)
                return 0;
        /* we have  start < mpnt->vm_end  */

        /* if it doesn't overlap, we have nothing.. */
        end = start + len;
        if (mpnt->vm_start >= end)
                return 0;

        /*
         * If we need to split any vma, do it now to save pain later.
         */
        if (start > mpnt->vm_start) {
                if (split_vma(mm, mpnt, start, 0))
                        return -ENOMEM;
                prev = mpnt;
                mpnt = mpnt->vm_next;
        }

        /* Does it split the last one? */
        last = find_vma(mm, end);
        if (last && end > last->vm_start) {
                if (split_vma(mm, last, end, 0))
                        return -ENOMEM;
        }

        /*
         * Remove the vma's, and unmap the actual pages
         */
        spin_lock(&mm->page_table_lock);
        mpnt = touched_by_munmap(mm, mpnt, prev, end);
        unmap_region(mm, mpnt, prev, start, end);
        spin_unlock(&mm->page_table_lock);

        /* Fix up all other VM information */
        unmap_vma_list(mm, mpnt);

        return 0;
}

asmlinkage long sys_munmap(unsigned long addr, size_t len)
{
        int ret;
        struct mm_struct *mm = current->mm;

        down_write(&mm->mmap_sem);
        ret = do_munmap(mm, addr, len);
        up_write(&mm->mmap_sem);
        return ret;
}

/*
 *  this is really a simplified "do_mmap".  it only handles
 *  anonymous maps.  eventually we may be able to do some
 *  brk-specific accounting here.
 */
unsigned long do_brk(unsigned long addr, unsigned long len)
{
        struct mm_struct * mm = current->mm;
        struct vm_area_struct * vma, * prev;
        unsigned long flags;
        struct rb_node ** rb_link, * rb_parent;

        len = PAGE_ALIGN(len);
        if (!len)
                return addr;

        /*
         * mlock MCL_FUTURE?
         */
        if (mm->def_flags & VM_LOCKED) {
                unsigned long locked = mm->locked_vm << PAGE_SHIFT;
                locked += len;
                if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
                        return -EAGAIN;
        }

        /*
         * Clear old maps.  this also does some error checking for us
         */
 munmap_back:
        vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
        if (vma && vma->vm_start < addr + len) {
                if (do_munmap(mm, addr, len))
                        return -ENOMEM;
                goto munmap_back;
        }

        /* Check against address space limits *after* clearing old maps... */
        if ((mm->total_vm << PAGE_SHIFT) + len
            > current->rlim[RLIMIT_AS].rlim_cur)
                return -ENOMEM;

        if (mm->map_count > MAX_MAP_COUNT)
                return -ENOMEM;

        if (!vm_enough_memory(len >> PAGE_SHIFT))
                return -ENOMEM;

        flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;

        /* Can we just expand an old anonymous mapping? */
        if (rb_parent && vma_merge(mm, prev, rb_parent, addr, addr + len, flags))
                goto out;

        /*
         * create a vma struct for an anonymous mapping
         */
        vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!vma) {
                vm_unacct_memory(len >> PAGE_SHIFT);
                return -ENOMEM;
        }

        vma->vm_mm = mm;
        vma->vm_start = addr;
        vma->vm_end = addr + len;
        vma->vm_flags = flags;
        vma->vm_page_prot = protection_map[flags & 0x0f];
        vma->vm_ops = NULL;
        vma->vm_pgoff = 0;
        vma->vm_file = NULL;
        vma->vm_private_data = NULL;

        vma_link(mm, vma, prev, rb_link, rb_parent);

out:
        mm->total_vm += len >> PAGE_SHIFT;
        if (flags & VM_LOCKED) {
                mm->locked_vm += len >> PAGE_SHIFT;
                make_pages_present(addr, addr + len);
        }
        return addr;
}

/* Build the RB tree corresponding to the VMA list. */
void build_mmap_rb(struct mm_struct * mm)
{
        struct vm_area_struct * vma;
        struct rb_node ** rb_link, * rb_parent;

        mm->mm_rb = RB_ROOT;
        rb_link = &mm->mm_rb.rb_node;
        rb_parent = NULL;
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
                __vma_link_rb(mm, vma, rb_link, rb_parent);
                rb_parent = &vma->vm_rb;
                rb_link = &rb_parent->rb_right;
        }
}

/* Release all mmaps. */
void exit_mmap(struct mm_struct * mm)
{
        mmu_gather_t *tlb;
        struct vm_area_struct * mpnt;

        release_segments(mm);
        spin_lock(&mm->page_table_lock);

        tlb = tlb_gather_mmu(mm, 1);

        flush_cache_mm(mm);
        mpnt = mm->mmap;
        while (mpnt) {
                unsigned long start = mpnt->vm_start;
                unsigned long end = mpnt->vm_end;

                /*
                 * If the VMA has been charged for, account for its
                 * removal
                 */
                if (mpnt->vm_flags & VM_ACCOUNT)
                        vm_unacct_memory((end - start) >> PAGE_SHIFT);

                mm->map_count--;
                if (!(is_vm_hugetlb_page(mpnt)))
                        unmap_page_range(tlb, mpnt, start, end);
                else
                        mpnt->vm_ops->close(mpnt);
                mpnt = mpnt->vm_next;
        }

        /* This is just debugging */
        if (mm->map_count)
                BUG();

        clear_page_tables(tlb, FIRST_USER_PGD_NR, USER_PTRS_PER_PGD);
        tlb_finish_mmu(tlb, 0, TASK_SIZE);

        mpnt = mm->mmap;
        mm->mmap = mm->mmap_cache = NULL;
        mm->mm_rb = RB_ROOT;
        mm->rss = 0;
        mm->total_vm = 0;
        mm->locked_vm = 0;

        spin_unlock(&mm->page_table_lock);

        /*
         * Walk the list again, actually closing and freeing it
         * without holding any MM locks.
         */
        while (mpnt) {
                struct vm_area_struct * next = mpnt->vm_next;
                remove_shared_vm_struct(mpnt);
                if (mpnt->vm_ops) {
                        if (mpnt->vm_ops->close)
                                mpnt->vm_ops->close(mpnt);
                }
                if (mpnt->vm_file)
                        fput(mpnt->vm_file);
                kmem_cache_free(vm_area_cachep, mpnt);
                mpnt = next;
        }
                
}

/* Insert vm structure into process list sorted by address
 * and into the inode's i_mmap ring.  If vm_file is non-NULL
 * then the i_shared_lock must be held here.
 */
void insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
{
        struct vm_area_struct * __vma, * prev;
        struct rb_node ** rb_link, * rb_parent;

        __vma = find_vma_prepare(mm, vma->vm_start, &prev, &rb_link, &rb_parent);
        if (__vma && __vma->vm_start < vma->vm_end)
                BUG();
        vma_link(mm, vma, prev, rb_link, rb_parent);
        validate_mm(mm);
}