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 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
  30 static 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         tmp.b_size = 1 << inode->i_blkbits;
  39         rc = ext2_get_block(inode, pgoff, &tmp, create);
  40         *result = tmp.b_blocknr;
  41
  42         /* did we get a sparse block (hole in the file)? */
  43         if (!tmp.b_blocknr && !rc) {
  44                 BUG_ON(create);
  45                 rc = -ENODATA;
  46         }
  47
  48         return rc;
  49 }
  50
  51 int
  52 ext2_clear_xip_target(struct inode *inode, sector_t block)
  53 {
  54         void *kaddr;
  55         unsigned long pfn;
  56         int rc;
  57
  58         rc = __inode_direct_access(inode, block, &kaddr, &pfn);
  59         if (!rc)
  60                 clear_page(kaddr);
  61         return rc;
  62 }
  63
  64 void ext2_xip_verify_sb(struct super_block *sb)
  65 {
  66         struct ext2_sb_info *sbi = EXT2_SB(sb);
  67
  68         if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  69             !sb->s_bdev->bd_disk->fops->direct_access) {
  70                 sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  71                 ext2_msg(sb, KERN_WARNING,
  72                              "warning: ignoring xip option - "
  73                              "not supported by bdev");
  74         }
  75 }
  76
  77 int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
  78                                 void **kmem, unsigned long *pfn)
  79 {
  80         int rc;
  81         sector_t block;
  82
  83         /* first, retrieve the sector number */
  84         rc = __ext2_get_block(mapping->host, pgoff, create, &block);
  85         if (rc)
  86                 return rc;
  87
  88         /* retrieve address of the target data */
  89         rc = __inode_direct_access(mapping->host, block, kmem, pfn);
  90         return rc;
  91 }