blockdev/linux/ext4_filedev.c

   1 /*
   2  * Copyright (c) 2013 Grzegorz Kostka (kostka.grzegorz@gmail.com)
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #define _FILE_OFFSET_BITS 64
  30
  31 #include <ext4_config.h>
  32 #include <ext4_blockdev.h>
  33 #include <ext4_errno.h>
  34 #include <stdio.h>
  35 #include <stdbool.h>
  36 #include <string.h>
  37 #include <fcntl.h>
  38
  39 /**@brief   Default filename.*/
  40 static const char *fname = "ext2";
  41
  42 /**@brief   Image block size.*/
  43 #define EXT4_FILEDEV_BSIZE 512
  44
  45 /**@brief   Image file descriptor.*/
  46 static FILE *dev_file;
  47
  48 #define DROP_LINUXCACHE_BUFFERS 0
  49
  50 /**********************BLOCKDEV INTERFACE**************************************/
  51 static int filedev_open(struct ext4_blockdev *bdev);
  52 static int filedev_bread(struct ext4_blockdev *bdev, void *buf, uint64_t blk_id,
  53                          uint32_t blk_cnt);
  54 static int filedev_bwrite(struct ext4_blockdev *bdev, const void *buf,
  55                           uint64_t blk_id, uint32_t blk_cnt);
  56 static int filedev_close(struct ext4_blockdev *bdev);
  57
  58 /******************************************************************************/
  59 EXT4_BLOCKDEV_STATIC_INSTANCE(_filedev, EXT4_FILEDEV_BSIZE, 0, filedev_open,
  60                               filedev_bread, filedev_bwrite, filedev_close);
  61
  62 /******************************************************************************/
  63 static int filedev_open(struct ext4_blockdev *bdev)
  64 {
  65         dev_file = fopen(fname, "r+b");
  66
  67         if (!dev_file)
  68                 return EIO;
  69
  70         /*No buffering at file.*/
  71         setbuf(dev_file, 0);
  72
  73         if (fseek(dev_file, 0, SEEK_END))
  74                 return EFAULT;
  75
  76         _filedev.ph_bcnt = ftell(dev_file) / _filedev.ph_bsize;
  77
  78         return EOK;
  79 }
  80
  81 /******************************************************************************/
  82
  83 static int filedev_bread(struct ext4_blockdev *bdev, void *buf, uint64_t blk_id,
  84                          uint32_t blk_cnt)
  85 {
  86         if (fseek(dev_file, blk_id * bdev->ph_bsize, SEEK_SET))
  87                 return EIO;
  88
  89         if (!fread(buf, bdev->ph_bsize * blk_cnt, 1, dev_file))
  90                 return EIO;
  91
  92         return EOK;
  93 }
  94
  95 static void drop_cache(void)
  96 {
  97 #if defined(__linux__) && DROP_LINUXCACHE_BUFFERS
  98         int fd;
  99         char *data = "3";
 100
 101         sync();
 102         fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
 103         write(fd, data, sizeof(char));
 104         close(fd);
 105 #endif
 106 }
 107
 108 /******************************************************************************/
 109 static int filedev_bwrite(struct ext4_blockdev *bdev, const void *buf,
 110                           uint64_t blk_id, uint32_t blk_cnt)
 111 {
 112         if (fseek(dev_file, blk_id * bdev->ph_bsize, SEEK_SET))
 113                 return EIO;
 114
 115         if (!fwrite(buf, bdev->ph_bsize * blk_cnt, 1, dev_file))
 116                 return EIO;
 117
 118         drop_cache();
 119         return EOK;
 120 }
 121 /******************************************************************************/
 122 static int filedev_close(struct ext4_blockdev *bdev)
 123 {
 124         fclose(dev_file);
 125         return EOK;
 126 }
 127
 128 /******************************************************************************/
 129 struct ext4_blockdev *ext4_filedev_get(void) { return &_filedev; }
 130 /******************************************************************************/
 131 void ext4_filedev_filename(const char *n) { fname = n; }
 132
 133 /******************************************************************************/