fs/ext2/xip.c

   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
  16 static inline long __inode_direct_access(struct inode *inode, sector_t block,
  17                                 void **kaddr, unsigned long *pfn, long size)
  18 {
  19         struct block_device *bdev = inode->i_sb->s_bdev;
  20         sector_t sector = block * (PAGE_SIZE / 512);
  21         return bdev_direct_access(bdev, sector, kaddr, pfn, size);
  22 }
  23
  24 static inline int
  25 __ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
  26                    sector_t *result)
  27 {
  28         struct buffer_head tmp;
  29         int rc;
  30
  31         memset(&tmp, 0, sizeof(struct buffer_head));
  32         tmp.b_size = 1 << inode->i_blkbits;
  33         rc = ext2_get_block(inode, pgoff, &tmp, create);
  34         *result = tmp.b_blocknr;
  35
  36         /* did we get a sparse block (hole in the file)? */
  37         if (!tmp.b_blocknr && !rc) {
  38                 BUG_ON(create);
  39                 rc = -ENODATA;
  40         }
  41
  42         return rc;
  43 }
  44
  45 void ext2_xip_verify_sb(struct super_block *sb)
  46 {
  47         struct ext2_sb_info *sbi = EXT2_SB(sb);
  48
  49         if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  50             !sb->s_bdev->bd_disk->fops->direct_access) {
  51                 sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  52                 ext2_msg(sb, KERN_WARNING,
  53                              "warning: ignoring xip option - "
  54                              "not supported by bdev");
  55         }
  56 }
  57
  58 int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
  59                                 void **kmem, unsigned long *pfn)
  60 {
  61         long rc;
  62         sector_t block;
  63
  64         /* first, retrieve the sector number */
  65         rc = __ext2_get_block(mapping->host, pgoff, create, &block);
  66         if (rc)
  67                 return rc;
  68
  69         /* retrieve address of the target data */
  70         rc = __inode_direct_access(mapping->host, block, kmem, pfn, PAGE_SIZE);
  71         return (rc < 0) ? rc : 0;
  72 }