root/fs/ext2/xip.c

DEFINITIONS

1. __inode_direct_access
2. __ext2_get_block
3. ext2_clear_xip_target
4. ext2_xip_verify_sb
5. ext2_get_xip_mem

/*
 *  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/ext2_fs_sb.h>
#include <linux/ext2_fs.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;
        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_warning(sb, __func__,
                             "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;
}