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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 block,
  19                       void **kaddr, unsigned long *pfn)
  20 {
  21         struct block_device *bdev = inode->i_sb->s_bdev;
  22         struct block_device_operations *ops = bdev->bd_disk->fops;
  23         sector_t sector;
  24
  25         sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */
  26
  27         BUG_ON(!ops->direct_access);
  28         return ops->direct_access(bdev, sector, kaddr, pfn);
  29 }
  30
  31 static inline int
  32 __ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
  33                    sector_t *result)
  34 {
  35         struct buffer_head tmp;
  36         int rc;
  37
  38         memset(&tmp, 0, sizeof(struct buffer_head));
  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_warning(sb, __func__,
  72                              "ignoring xip option - not supported by bdev");
  73         }
  74 }
  75
  76 int 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 }