linux/fs/ext2/xip.c
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   1/*
   2 *  linux/fs/ext2/xip.c
   3 *
   4 * Copyright (C) 2005 IBM Corporation
   5 * Author: Carsten Otte (cotte@de.ibm.com)
   6 */
   7
   8#include <linux/mm.h>
   9#include <linux/fs.h>
  10#include <linux/genhd.h>
  11#include <linux/buffer_head.h>
  12#include <linux/blkdev.h>
  13#include "ext2.h"
  14#include "xip.h"
  15
  16static inline int
  17__inode_direct_access(struct inode *inode, sector_t block,
  18                      void **kaddr, unsigned long *pfn)
  19{
  20        struct block_device *bdev = inode->i_sb->s_bdev;
  21        const struct block_device_operations *ops = bdev->bd_disk->fops;
  22        sector_t sector;
  23
  24        sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */
  25
  26        BUG_ON(!ops->direct_access);
  27        return ops->direct_access(bdev, sector, kaddr, pfn);
  28}
  29
  30static inline int
  31__ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
  32                   sector_t *result)
  33{
  34        struct buffer_head tmp;
  35        int rc;
  36
  37        memset(&tmp, 0, sizeof(struct buffer_head));
  38        rc = ext2_get_block(inode, pgoff, &tmp, create);
  39        *result = tmp.b_blocknr;
  40
  41        /* did we get a sparse block (hole in the file)? */
  42        if (!tmp.b_blocknr && !rc) {
  43                BUG_ON(create);
  44                rc = -ENODATA;
  45        }
  46
  47        return rc;
  48}
  49
  50int
  51ext2_clear_xip_target(struct inode *inode, sector_t block)
  52{
  53        void *kaddr;
  54        unsigned long pfn;
  55        int rc;
  56
  57        rc = __inode_direct_access(inode, block, &kaddr, &pfn);
  58        if (!rc)
  59                clear_page(kaddr);
  60        return rc;
  61}
  62
  63void ext2_xip_verify_sb(struct super_block *sb)
  64{
  65        struct ext2_sb_info *sbi = EXT2_SB(sb);
  66
  67        if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  68            !sb->s_bdev->bd_disk->fops->direct_access) {
  69                sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  70                ext2_msg(sb, KERN_WARNING,
  71                             "warning: ignoring xip option - "
  72                             "not supported by bdev");
  73        }
  74}
  75
  76int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
  77                                void **kmem, unsigned long *pfn)
  78{
  79        int rc;
  80        sector_t block;
  81
  82        /* first, retrieve the sector number */
  83        rc = __ext2_get_block(mapping->host, pgoff, create, &block);
  84        if (rc)
  85                return rc;
  86
  87        /* retrieve address of the target data */
  88        rc = __inode_direct_access(mapping->host, block, kmem, pfn);
  89        return rc;
  90}
  91
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