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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/ext2_fs_sb.h>
  13 #include <linux/ext2_fs.h>
  14 #include "ext2.h"
  15 #include "xip.h"
  16
  17 static inline int
  18 __inode_direct_access(struct inode *inode, sector_t sector,
  19                       unsigned long *data)
  20 {
  21         BUG_ON(!inode->i_sb->s_bdev->bd_disk->fops->direct_access);
  22         return inode->i_sb->s_bdev->bd_disk->fops
  23                 ->direct_access(inode->i_sb->s_bdev,sector,data);
  24 }
  25
  26 static inline int
  27 __ext2_get_sector(struct inode *inode, sector_t offset, int create,
  28                    sector_t *result)
  29 {
  30         struct buffer_head tmp;
  31         int rc;
  32
  33         memset(&tmp, 0, sizeof(struct buffer_head));
  34         rc = ext2_get_block(inode, offset/ (PAGE_SIZE/512), &tmp,
  35                             create);
  36         *result = tmp.b_blocknr;
  37
  38         /* did we get a sparse block (hole in the file)? */
  39         if (!tmp.b_blocknr && !rc) {
  40                 BUG_ON(create);
  41                 rc = -ENODATA;
  42         }
  43
  44         return rc;
  45 }
  46
  47 int
  48 ext2_clear_xip_target(struct inode *inode, int block)
  49 {
  50         sector_t sector = block * (PAGE_SIZE/512);
  51         unsigned long data;
  52         int rc;
  53
  54         rc = __inode_direct_access(inode, sector, &data);
  55         if (!rc)
  56                 clear_page((void*)data);
  57         return rc;
  58 }
  59
  60 void ext2_xip_verify_sb(struct super_block *sb)
  61 {
  62         struct ext2_sb_info *sbi = EXT2_SB(sb);
  63
  64         if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  65             !sb->s_bdev->bd_disk->fops->direct_access) {
  66                 sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  67                 ext2_warning(sb, __FUNCTION__,
  68                              "ignoring xip option - not supported by bdev");
  69         }
  70 }
  71
  72 struct page *
  73 ext2_get_xip_page(struct address_space *mapping, sector_t offset,
  74                    int create)
  75 {
  76         int rc;
  77         unsigned long data;
  78         sector_t sector;
  79
  80         /* first, retrieve the sector number */
  81         rc = __ext2_get_sector(mapping->host, offset, create, &sector);
  82         if (rc)
  83                 goto error;
  84
  85         /* retrieve address of the target data */
  86         rc = __inode_direct_access
  87                 (mapping->host, sector * (PAGE_SIZE/512), &data);
  88         if (!rc)
  89                 return virt_to_page(data);
  90
  91  error:
  92         return ERR_PTR(rc);
  93 }