/*
 *      linux/mm/msync.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * The msync() system call.
 */
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/mm.h>
#include <linux/mman.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

/*
 * Called with mm->page_table_lock held to protect against other
 * threads/the swapper from ripping pte's out from under us.
 */
static int filemap_sync_pte(pte_t *ptep, struct vm_area_struct *vma,
        unsigned long address, unsigned int flags)
{
        pte_t pte = *ptep;

        if (pte_present(pte) && pte_dirty(pte)) {
                struct page *page;
                unsigned long pfn = pte_pfn(pte);
                if (pfn_valid(pfn)) {
                        page = pfn_to_page(pfn);
                        if (!PageReserved(page) && ptep_test_and_clear_dirty(ptep)) {
                                flush_tlb_page(vma, address);
                                set_page_dirty(page);
                        }
                }
        }
        return 0;
}

static inline int filemap_sync_pte_range(pmd_t * pmd,
        unsigned long address, unsigned long end, 
        struct vm_area_struct *vma, unsigned int flags)
{
        pte_t *pte;
        int error;

        if (pmd_none(*pmd))
                return 0;
        if (pmd_bad(*pmd)) {
                pmd_ERROR(*pmd);
                pmd_clear(pmd);
                return 0;
        }
        pte = pte_offset_map(pmd, address);
        if ((address & PMD_MASK) != (end & PMD_MASK))
                end = (address & PMD_MASK) + PMD_SIZE;
        error = 0;
        do {
                error |= filemap_sync_pte(pte, vma, address, flags);
                address += PAGE_SIZE;
                pte++;
        } while (address && (address < end));

        pte_unmap(pte - 1);

        return error;
}

static inline int filemap_sync_pmd_range(pgd_t * pgd,
        unsigned long address, unsigned long end, 
        struct vm_area_struct *vma, unsigned int flags)
{
        pmd_t * pmd;
        int error;

        if (pgd_none(*pgd))
                return 0;
        if (pgd_bad(*pgd)) {
                pgd_ERROR(*pgd);
                pgd_clear(pgd);
                return 0;
        }
        pmd = pmd_offset(pgd, address);
        if ((address & PGDIR_MASK) != (end & PGDIR_MASK))
                end = (address & PGDIR_MASK) + PGDIR_SIZE;
        error = 0;
        do {
                error |= filemap_sync_pte_range(pmd, address, end, vma, flags);
                address = (address + PMD_SIZE) & PMD_MASK;
                pmd++;
        } while (address && (address < end));
        return error;
}

int filemap_sync(struct vm_area_struct * vma, unsigned long address,
        size_t size, unsigned int flags)
{
        pgd_t * dir;
        unsigned long end = address + size;
        int error = 0;

        /* Aquire the lock early; it may be possible to avoid dropping
         * and reaquiring it repeatedly.
         */
        spin_lock(&vma->vm_mm->page_table_lock);

        dir = pgd_offset(vma->vm_mm, address);
        flush_cache_range(vma, address, end);
        if (address >= end)
                BUG();
        do {
                error |= filemap_sync_pmd_range(dir, address, end, vma, flags);
                address = (address + PGDIR_SIZE) & PGDIR_MASK;
                dir++;
        } while (address && (address < end));
        flush_tlb_range(vma, end - size, end);

        spin_unlock(&vma->vm_mm->page_table_lock);

        return error;
}

/*
 * MS_SYNC syncs the entire file - including mappings.
 *
 * MS_ASYNC initiates writeout of just the dirty mapped data.
 * This provides no guarantee of file integrity - things like indirect
 * blocks may not have started writeout.  MS_ASYNC is primarily useful
 * where the application knows that it has finished with the data and
 * wishes to intelligently schedule its own I/O traffic.
 */
static int msync_interval(struct vm_area_struct * vma,
        unsigned long start, unsigned long end, int flags)
{
        int ret = 0;
        struct file * file = vma->vm_file;

        if (file && (vma->vm_flags & VM_SHARED)) {
                ret = filemap_sync(vma, start, end-start, flags);

                if (!ret && (flags & (MS_SYNC|MS_ASYNC))) {
                        struct inode * inode = file->f_dentry->d_inode;
                        int err;

                        down(&inode->i_sem);
                        ret = filemap_fdatawrite(inode->i_mapping);
                        if (flags & MS_SYNC) {
                                if (file->f_op && file->f_op->fsync) {
                                        err = file->f_op->fsync(file, file->f_dentry, 1);
                                        if (err && !ret)
                                                ret = err;
                                }
                                err = filemap_fdatawait(inode->i_mapping);
                                if (!ret)
                                        ret = err;
                        }
                        up(&inode->i_sem);
                }
        }
        return ret;
}

asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
{
        unsigned long end;
        struct vm_area_struct * vma;
        int unmapped_error, error = -EINVAL;

        down_read(&current->mm->mmap_sem);
        if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
                goto out;
        if (start & ~PAGE_MASK)
                goto out;
        error = -ENOMEM;
        len = (len + ~PAGE_MASK) & PAGE_MASK;
        end = start + len;
        if (end < start)
                goto out;
        error = 0;
        if (end == start)
                goto out;
        /*
         * If the interval [start,end) covers some unmapped address ranges,
         * just ignore them, but return -ENOMEM at the end.
         */
        vma = find_vma(current->mm, start);
        unmapped_error = 0;
        for (;;) {
                /* Still start < end. */
                error = -ENOMEM;
                if (!vma)
                        goto out;
                /* Here start < vma->vm_end. */
                if (start < vma->vm_start) {
                        unmapped_error = -ENOMEM;
                        start = vma->vm_start;
                }
                /* Here vma->vm_start <= start < vma->vm_end. */
                if (end <= vma->vm_end) {
                        if (start < end) {
                                error = msync_interval(vma, start, end, flags);
                                if (error)
                                        goto out;
                        }
                        error = unmapped_error;
                        goto out;
                }
                /* Here vma->vm_start <= start < vma->vm_end < end. */
                error = msync_interval(vma, start, vma->vm_end, flags);
                if (error)
                        goto out;
                start = vma->vm_end;
                vma = vma->vm_next;
        }
out:
        up_read(&current->mm->mmap_sem);
        return error;
}