mmap.c

来自「elinux jffs初始版本 具体了解JFFS的文件系统！」· C语言 代码 · 共 156 行

/*
 *  mmap.c
 *
 *  Copyright (C) 1995, 1996 by Volker Lendecke
 *
 */

#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/fcntl.h>
#include <linux/ncp_fs.h>

#include "ncplib_kernel.h"
#include <asm/segment.h>
#include <asm/system.h>

static inline int min(int a, int b)
{
	return a<b ? a : b;
}

/*
 * Fill in the supplied page for mmap
 */
static unsigned long 
ncp_file_mmap_nopage(struct vm_area_struct * area,
		     unsigned long address, int no_share)
{
	struct inode * inode = area->vm_inode;
	unsigned long page;
	unsigned int clear;
	unsigned long tmp;
	int bufsize;
	int pos;
	unsigned short fs;

	page = __get_free_page(GFP_KERNEL);
	if (!page)
		return page;
	address &= PAGE_MASK;
	pos = address - area->vm_start + area->vm_offset;

	clear = 0;
	if (address + PAGE_SIZE > area->vm_end)
	{
		clear = address + PAGE_SIZE - area->vm_end;
	}

        /* what we can read in one go */
	bufsize = NCP_SERVER(inode)->buffer_size;

	fs = get_fs();
	set_fs(get_ds());

        if (ncp_make_open(inode, O_RDONLY) < 0)
	{
                clear = PAGE_SIZE;
        }
        else
        {
		int already_read = 0;
		int count = PAGE_SIZE - clear;
		int to_read;

		while (already_read < count)
		{
			int read_this_time;

			if ((pos % bufsize) != 0)
			{
				to_read = bufsize - (pos % bufsize);
			}
			else
			{
				to_read = bufsize;
			}

			to_read = min(to_read, count - already_read);

			if (ncp_read(NCP_SERVER(inode),
				     NCP_FINFO(inode)->file_handle,
				     pos, to_read,
				     (char *)(page + already_read),
				     &read_this_time) != 0)
			{
			       read_this_time = 0;
			}

			pos += read_this_time;
			already_read += read_this_time;

			if (read_this_time < to_read)
			{
				break;
			}
		}

        }

	set_fs(fs);

	tmp = page + PAGE_SIZE;
	while (clear--) {
		*(char *)--tmp = 0;
	}
	return page;
}

struct vm_operations_struct ncp_file_mmap = {
	NULL,			/* open */
	NULL,			/* close */
	NULL,			/* unmap */
	NULL,			/* protect */
	NULL,			/* sync */
	NULL,			/* advise */
	ncp_file_mmap_nopage,	/* nopage */
	NULL,			/* wppage */
	NULL,			/* swapout */
	NULL,			/* swapin */
};


/* This is used for a general mmap of a ncp file */
int
ncp_mmap(struct inode * inode, struct file * file, struct vm_area_struct * vma)
{
        DPRINTK("ncp_mmap: called\n");

	if (!ncp_conn_valid(NCP_SERVER(inode)))
	{
		return -EIO;
	}

        /* only PAGE_COW or read-only supported now */
	if (vma->vm_flags & VM_SHARED)	
		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;
	inode->i_count++;
	vma->vm_ops = &ncp_file_mmap;
	return 0;
}