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/*
* linux/fs/fat/mmap.c
*
* Written by Jacques Gelinas (jacques@solucorp.qc.ca)
* Inspired by fs/nfs/mmap.c (Jon Tombs 15 Aug 1993)
*
* mmap handling for fat-based filesystems
*/
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/shm.h>
#include <linux/errno.h>
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/msdos_fs.h>
#include <asm/uaccess.h>
#include <asm/system.h>
/*
* Fill in the supplied page for mmap
*/
static unsigned long fat_file_mmap_nopage(
struct vm_area_struct * area,
unsigned long address,
int error_code)
{
struct inode * inode = area->vm_inode;
unsigned long page;
unsigned int clear;
int pos;
long gap; /* distance from eof to pos */
page = __get_free_page(GFP_KERNEL);
if (!page)
return page;
address &= PAGE_MASK;
pos = address - area->vm_start + area->vm_offset;
clear = 0;
gap = inode->i_size - pos;
if (gap <= 0){
/* mmaping beyond end of file */
clear = PAGE_SIZE;
}else{
int cur_read;
int need_read;
struct file filp;
if (gap < PAGE_SIZE){
clear = PAGE_SIZE - gap;
}
filp.f_reada = 0;
filp.f_pos = pos;
need_read = PAGE_SIZE - clear;
{
unsigned long cur_fs = get_fs();
set_fs (KERNEL_DS);
cur_read = fat_file_read (inode,&filp,(char*)page
,need_read);
set_fs (cur_fs);
}
if (cur_read != need_read){
printk ("MSDOS: Error while reading an mmap file %d <> %d\n"
,cur_read,need_read);
}
}
if (clear > 0){
memset ((char*)page+PAGE_SIZE-clear,0,clear);
}
return page;
}
struct vm_operations_struct fat_file_mmap = {
NULL, /* open */
NULL, /* close */
NULL, /* unmap */
NULL, /* protect */
NULL, /* sync */
NULL, /* advise */
fat_file_mmap_nopage, /* nopage */
NULL, /* wppage */
NULL, /* swapout */
NULL, /* swapin */
};
/*
* This is used for a general mmap of an msdos file
* Returns 0 if ok, or a negative error code if not.
*/
int fat_mmap(struct inode * inode, struct file * file, struct vm_area_struct * vma)
{
if (vma->vm_flags & VM_SHARED) /* only PAGE_COW or read-only supported now */
return -EINVAL;
if (vma->vm_offset & (inode->i_sb->s_blocksize - 1))
return -EINVAL;
if (!inode->i_sb || !S_ISREG(inode->i_mode))
return -EACCES;
if (!IS_RDONLY(inode)) {
inode->i_atime = CURRENT_TIME;
inode->i_dirt = 1;
}
vma->vm_inode = inode;
atomic_inc(&inode->i_count);
vma->vm_ops = &fat_file_mmap;
return 0;
}
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