text: /*
   *	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 <linux/hugetlb.h>
  #include <linux/syscalls.h>
  
  #include <asm/pgtable.h>
  #include <asm/tlbflush.h>
  
  static void msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
  				unsigned long addr, unsigned long end)
  {
  	pte_t *pte;
  	spinlock_t *ptl;
  	int progress = 0;
  
  again:
  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  	do {
  		struct page *page;
  
  		if (progress >= 64) {
  			progress = 0;
  			if (need_resched() || need_lockbreak(ptl))
  				break;
  		}
  		progress++;
  		if (!pte_present(*pte))
  			continue;
  		if (!pte_maybe_dirty(*pte))
  			continue;
  		page = vm_normal_page(vma, addr, *pte);
  		if (!page)
  			continue;
  		if (ptep_clear_flush_dirty(vma, addr, pte) ||
  		    page_test_and_clear_dirty(page))
  			set_page_dirty(page);
  		progress += 3;
  	} while (pte++, addr += PAGE_SIZE, addr != end);
  	pte_unmap_unlock(pte - 1, ptl);
  	cond_resched();
  	if (addr != end)
  		goto again;
  }
  
  static inline void msync_pmd_range(struct vm_area_struct *vma, pud_t *pud,
  				unsigned long addr, unsigned long end)
  {
  	pmd_t *pmd;
  	unsigned long next;
  
  	pmd = pmd_offset(pud, addr);
  	do {
  		next = pmd_addr_end(addr, end);
  		if (pmd_none_or_clear_bad(pmd))
  			continue;
  		msync_pte_range(vma, pmd, addr, next);
  	} while (pmd++, addr = next, addr != end);
  }
  
  static inline void msync_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
  				unsigned long addr, unsigned long end)
  {
  	pud_t *pud;
  	unsigned long next;
  
  	pud = pud_offset(pgd, addr);
  	do {
  		next = pud_addr_end(addr, end);
  		if (pud_none_or_clear_bad(pud))
  			continue;
  		msync_pmd_range(vma, pud, addr, next);
  	} while (pud++, addr = next, addr != end);
  }
  
  static void msync_page_range(struct vm_area_struct *vma,
  				unsigned long addr, unsigned long end)
  {
  	pgd_t *pgd;
  	unsigned long next;
  
  	/* For hugepages we can't go walking the page table normally,
  	 * but that's ok, hugetlbfs is memory based, so we don't need
  	 * to do anything more on an msync().
  	 */
  	if (vma->vm_flags & VM_HUGETLB)
  		return;
  
  	BUG_ON(addr >= end);
  	pgd = pgd_offset(vma->vm_mm, addr);
  	flush_cache_range(vma, addr, end);
  	do {
  		next = pgd_addr_end(addr, end);
  		if (pgd_none_or_clear_bad(pgd))
  			continue;
  		msync_pud_range(vma, pgd, addr, next);
  	} while (pgd++, addr = next, addr != end);
  }
  
  /*
   * MS_SYNC syncs the entire file - including mappings.
   *
   * MS_ASYNC does not start I/O (it used to, up to 2.5.67).  Instead, it just
   * marks the relevant pages dirty.  The application may now run fsync() to
   * write out the dirty pages and wait on the writeout and check the result.
   * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
   * async writeout immediately.
   * So my _not_ starting I/O in MS_ASYNC we provide complete flexibility to
   * applications.
   */
  static int msync_interval(struct vm_area_struct *vma,
  			unsigned long addr, unsigned long end, int flags)
  {
  	int ret = 0;
  	struct file *file = vma->vm_file;
  
  	if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
  		return -EBUSY;
  
  	if (file && (vma->vm_flags & VM_SHARED)) {
  		msync_page_range(vma, addr, end);
  
  		if (flags & MS_SYNC) {
  			struct address_space *mapping = file->f_mapping;
  			int err;
  
  			ret = filemap_fdatawrite(mapping);
  			if (file->f_op && file->f_op->fsync) {
  				/*
  				 * We don't take i_mutex here because mmap_sem
  				 * is already held.
  				 */
  				err = file->f_op->fsync(file,file->f_dentry,1);
  				if (err && !ret)
  					ret = err;
  			}
  			err = filemap_fdatawait(mapping);
  			if (!ret)
  				ret = err;
  		}
  	}
  	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;
  
  	if (flags & MS_SYNC)
  		current->flags |= PF_SYNCWRITE;
  
  	down_read(&current->mm->mmap_sem);
  	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
  		goto out;
  	if (start & ~PAGE_MASK)
  		goto out;
  	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
  		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);
  	current->flags &= ~PF_SYNCWRITE;
  	return error;
  }
  