original development tree for Linux kernel GTP module; now long in mainline.
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/*
* linux/fs/ext2/xip.c
*
* Copyright (C) 2005 IBM Corporation
* Author: Carsten Otte (cotte@de.ibm.com)
*/
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include "ext2.h"
#include "xip.h"
static inline int
__inode_direct_access(struct inode *inode, sector_t block,
void **kaddr, unsigned long *pfn)
{
struct block_device *bdev = inode->i_sb->s_bdev;
const struct block_device_operations *ops = bdev->bd_disk->fops;
sector_t sector;
sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */
BUG_ON(!ops->direct_access);
return ops->direct_access(bdev, sector, kaddr, pfn);
}
static inline int
__ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
sector_t *result)
{
struct buffer_head tmp;
int rc;
memset(&tmp, 0, sizeof(struct buffer_head));
rc = ext2_get_block(inode, pgoff, &tmp, create);
*result = tmp.b_blocknr;
/* did we get a sparse block (hole in the file)? */
if (!tmp.b_blocknr && !rc) {
BUG_ON(create);
rc = -ENODATA;
}
return rc;
}
int
ext2_clear_xip_target(struct inode *inode, sector_t block)
{
void *kaddr;
unsigned long pfn;
int rc;
rc = __inode_direct_access(inode, block, &kaddr, &pfn);
if (!rc)
clear_page(kaddr);
return rc;
}
void ext2_xip_verify_sb(struct super_block *sb)
{
struct ext2_sb_info *sbi = EXT2_SB(sb);
if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
!sb->s_bdev->bd_disk->fops->direct_access) {
sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
ext2_msg(sb, KERN_WARNING,
"warning: ignoring xip option - "
"not supported by bdev");
}
}
int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
void **kmem, unsigned long *pfn)
{
int rc;
sector_t block;
/* first, retrieve the sector number */
rc = __ext2_get_block(mapping->host, pgoff, create, &block);
if (rc)
return rc;
/* retrieve address of the target data */
rc = __inode_direct_access(mapping->host, block, kmem, pfn);
return rc;
}