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 "ext2.h"
  15 #include "xip.h"
  16
  17 static inline int
  18 __inode_direct_access(struct inode *inode, sector_t sector,
  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
  24         BUG_ON(!ops->direct_access);
  25         return ops->direct_access(bdev, sector, kaddr, pfn);
  26 }
  27
  28 static inline int
  29 __ext2_get_sector(struct inode *inode, sector_t offset, int create,
  30                    sector_t *result)
  31 {
  32         struct buffer_head tmp;
  33         int rc;
  34
  35         memset(&tmp, 0, sizeof(struct buffer_head));
  36         rc = ext2_get_block(inode, offset/ (PAGE_SIZE/512), &tmp,
  37                             create);
  38         *result = tmp.b_blocknr;
  39
  40         /* did we get a sparse block (hole in the file)? */
  41         if (!tmp.b_blocknr && !rc) {
  42                 BUG_ON(create);
  43                 rc = -ENODATA;
  44         }
  45
  46         return rc;
  47 }
  48
  49 int
  50 ext2_clear_xip_target(struct inode *inode, int block)
  51 {
  52         sector_t sector = block * (PAGE_SIZE/512);
  53         void *kaddr;
  54         unsigned long pfn;
  55         int rc;
  56
  57         rc = __inode_direct_access(inode, sector, &kaddr, &pfn);
  58         if (!rc)
  59                 clear_page(kaddr);
  60         return rc;
  61 }
  62
  63 void ext2_xip_verify_sb(struct super_block *sb)
  64 {
  65         struct ext2_sb_info *sbi = EXT2_SB(sb);
  66
  67         if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  68             !sb->s_bdev->bd_disk->fops->direct_access) {
  69                 sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);
  70                 ext2_warning(sb, __FUNCTION__,
  71                              "ignoring xip option - not supported by bdev");
  72         }
  73 }
  74
  75 struct page *
  76 ext2_get_xip_page(struct address_space *mapping, sector_t offset,
  77                    int create)
  78 {
  79         int rc;
  80         void *kaddr;
  81         unsigned long pfn;
  82         sector_t sector;
  83
  84         /* first, retrieve the sector number */
  85         rc = __ext2_get_sector(mapping->host, offset, create, &sector);
  86         if (rc)
  87                 goto error;
  88
  89         /* retrieve address of the target data */
  90         rc = __inode_direct_access
  91                 (mapping->host, sector * (PAGE_SIZE/512), &kaddr, &pfn);
  92         if (!rc)
  93                 return pfn_to_page(pfn);
  94
  95  error:
  96         return ERR_PTR(rc);
  97 }