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/ext2_fs_sb.h>
  13 #include <linux/ext2_fs.h>
  14 #include <linux/blkdev.h>
  15 #include "ext2.h"
  16 #include "xip.h"
  17
  18 static inline int
  19 __inode_direct_access(struct inode *inode, sector_t block,
  20                       void **kaddr, unsigned long *pfn)
  21 {
  22         struct block_device *bdev = inode->i_sb->s_bdev;
  23         const struct block_device_operations *ops = bdev->bd_disk->fops;
  24         sector_t sector;
  25
  26         sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */
  27
  28         BUG_ON(!ops->direct_access);
  29         return ops->direct_access(bdev, sector, kaddr, pfn);
  30 }
  31
  32 static inline int
  33 __ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
  34                    sector_t *result)
  35 {
  36         struct buffer_head tmp;
  37         int rc;
  38
  39         memset(&tmp, 0, sizeof(struct buffer_head));
  40         rc = ext2_get_block(inode, pgoff, &tmp, create);
  41         *result = tmp.b_blocknr;
  42
  43         /* did we get a sparse block (hole in the file)? */
  44         if (!tmp.b_blocknr && !rc) {
  45                 BUG_ON(create);
  46                 rc = -ENODATA;
  47         }
  48
  49         return rc;
  50 }
  51
  52 int
  53 ext2_clear_xip_target(struct inode *inode, sector_t block)
  54 {
  55         void *kaddr;
  56         unsigned long pfn;
  57         int rc;
  58
  59         rc = __inode_direct_access(inode, block, &kaddr, &pfn);
  60         if (!rc)
  61                 clear_page(kaddr);
  62         return rc;
  63 }
  64
  65 void ext2_xip_verify_sb(struct super_block *sb)
  66 {
  67         struct ext2_sb_info *sbi = EXT2_SB(sb);
  68
  69         if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  70             !sb->s_bdev->bd_disk->fops->direct_access) {
  71                 sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  72                 ext2_msg(sb, KERN_WARNING,
  73                              "warning: ignoring xip option - "
  74                              "not supported by bdev");
  75         }
  76 }
  77
  78 int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
  79                                 void **kmem, unsigned long *pfn)
  80 {
  81         int rc;
  82         sector_t block;
  83
  84         /* first, retrieve the sector number */
  85         rc = __ext2_get_block(mapping->host, pgoff, create, &block);
  86         if (rc)
  87                 return rc;
  88
  89         /* retrieve address of the target data */
  90         rc = __inode_direct_access(mapping->host, block, kmem, pfn);
  91         return rc;
  92 }