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         rc = ext2_get_block(inode, pgoff, &tmp, create);
  39         *result = tmp.b_blocknr;
  40
  41         /* did we get a sparse block (hole in the file)? */
  42         if (!tmp.b_blocknr && !rc) {
  43                 BUG_ON(create);
  44                 rc = -ENODATA;
  45         }
  46
  47         return rc;
  48 }
  49
  50 int
  51 ext2_clear_xip_target(struct inode *inode, sector_t block)
  52 {
  53         void *kaddr;
  54         unsigned long pfn;
  55         int rc;
  56
  57         rc = __inode_direct_access(inode, block, &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_msg(sb, KERN_WARNING,
  71                              "warning: ignoring xip option - "
  72                              "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 }