xip.c

Go to the documentation of this file.

/*
 *  linux/fs/ext2/xip.c
 *
 * Copyright (C) 2005 IBM Corporation
 * Author: Carsten Otte ([email protected])
 */

#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;
}