/*
   * mm/fadvise.c
   *
   * Copyright (C) 2002, Linus Torvalds
   *

   * 11Jan2003	Andrew Morton

   *		Initial version.
   */
  
  #include <linux/kernel.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/backing-dev.h>
  #include <linux/pagevec.h>
  #include <linux/fadvise.h>

  #include <linux/writeback.h>

  #include <linux/syscalls.h>
  
  #include <asm/unistd.h>
  
  /*
   * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
   * deactivate the pages and clear PG_Referenced.
   */
  asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  {
  	struct file *file = fget(fd);
  	struct address_space *mapping;
  	struct backing_dev_info *bdi;

  	loff_t endbyte;			/* inclusive */

  	pgoff_t start_index;
  	pgoff_t end_index;
  	unsigned long nrpages;
  	int ret = 0;
  
  	if (!file)
  		return -EBADF;

  	if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) {

  		ret = -ESPIPE;
  		goto out;
  	}

  	mapping = file->f_mapping;
  	if (!mapping || len < 0) {
  		ret = -EINVAL;
  		goto out;
  	}

  	if (mapping->a_ops->get_xip_mem) {

  		switch (advice) {
  		case POSIX_FADV_NORMAL:
  		case POSIX_FADV_RANDOM:
  		case POSIX_FADV_SEQUENTIAL:
  		case POSIX_FADV_WILLNEED:
  		case POSIX_FADV_NOREUSE:
  		case POSIX_FADV_DONTNEED:
  			/* no bad return value, but ignore advice */
  			break;
  		default:
  			ret = -EINVAL;
  		}

  		goto out;

  	}

  	/* Careful about overflows. Len == 0 means "as much as possible" */
  	endbyte = offset + len;
  	if (!len || endbyte < len)
  		endbyte = -1;

  	else
  		endbyte--;		/* inclusive */

  
  	bdi = mapping->backing_dev_info;
  
  	switch (advice) {
  	case POSIX_FADV_NORMAL:
  		file->f_ra.ra_pages = bdi->ra_pages;
  		break;
  	case POSIX_FADV_RANDOM:
  		file->f_ra.ra_pages = 0;
  		break;
  	case POSIX_FADV_SEQUENTIAL:
  		file->f_ra.ra_pages = bdi->ra_pages * 2;
  		break;
  	case POSIX_FADV_WILLNEED:

  		if (!mapping->a_ops->readpage) {
  			ret = -EINVAL;
  			break;
  		}
  
  		/* First and last PARTIAL page! */
  		start_index = offset >> PAGE_CACHE_SHIFT;

  		end_index = endbyte >> PAGE_CACHE_SHIFT;

  
  		/* Careful about overflow on the "+1" */
  		nrpages = end_index - start_index + 1;
  		if (!nrpages)
  			nrpages = ~0UL;
  		
  		ret = force_page_cache_readahead(mapping, file,
  				start_index,
  				max_sane_readahead(nrpages));
  		if (ret > 0)
  			ret = 0;
  		break;

  	case POSIX_FADV_NOREUSE:
  		break;

  	case POSIX_FADV_DONTNEED:
  		if (!bdi_write_congested(mapping->backing_dev_info))
  			filemap_flush(mapping);
  
  		/* First and last FULL page! */

  		start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;

  		end_index = (endbyte >> PAGE_CACHE_SHIFT);

  		if (end_index >= start_index)
  			invalidate_mapping_pages(mapping, start_index,
  						end_index);
  		break;

  	default:
  		ret = -EINVAL;
  	}
  out:
  	fput(file);
  	return ret;
  }
  
  #ifdef __ARCH_WANT_SYS_FADVISE64
  
  asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
  {
  	return sys_fadvise64_64(fd, offset, len, advice);
  }
  
  #endif