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 _LARGEFILE64_SOURCE
  30 #define _FILE_OFFSET_BITS 64
  31
  32 #include <ext4_config.h>
  33 #include <ext4_blockdev.h>
  34 #include <ext4_errno.h>
  35 #include <stdio.h>
  36 #include <stdbool.h>
  37 #include <string.h>
  38 #include <fcntl.h>
  39
  40 /**@brief   Default filename.*/
  41 static const char *fname = "ext2";
  42
  43 /**@brief   Image block size.*/
  44 #define EXT4_FILEDEV_BSIZE 512
  45
  46 /**@brief   Image file descriptor.*/
  47 static FILE *dev_file;
  48
  49 #define DROP_LINUXCACHE_BUFFERS 0
  50
  51 /**********************BLOCKDEV INTERFACE**************************************/
  52 static int filedev_open(struct ext4_blockdev *bdev);
  53 static int filedev_bread(struct ext4_blockdev *bdev, void *buf, uint64_t blk_id,
  54                          uint32_t blk_cnt);
  55 static int filedev_bwrite(struct ext4_blockdev *bdev, const void *buf,
  56                           uint64_t blk_id, uint32_t blk_cnt);
  57 static int filedev_close(struct ext4_blockdev *bdev);
  58
  59 /******************************************************************************/
  60 EXT4_BLOCKDEV_STATIC_INSTANCE(_filedev, EXT4_FILEDEV_BSIZE, 0, filedev_open,
  61                 filedev_bread, filedev_bwrite, filedev_close, 0, 0);
  62
  63 /******************************************************************************/
  64 static int filedev_open(struct ext4_blockdev *bdev)
  65 {
  66         dev_file = fopen(fname, "r+b");
  67
  68         if (!dev_file)
  69                 return EIO;
  70
  71         /*No buffering at file.*/
  72         setbuf(dev_file, 0);
  73
  74         if (fseeko(dev_file, 0, SEEK_END))
  75                 return EFAULT;
  76
  77         _filedev.bdif->ph_bcnt = ftell(dev_file) / _filedev.bdif->ph_bsize;
  78
  79         return EOK;
  80 }
  81
  82 /******************************************************************************/
  83
  84 static int filedev_bread(struct ext4_blockdev *bdev, void *buf, uint64_t blk_id,
  85                          uint32_t blk_cnt)
  86 {
  87         if (fseeko(dev_file, blk_id * bdev->bdif->ph_bsize, SEEK_SET))
  88                 return EIO;
  89         if (!blk_cnt)
  90                 return EOK;
  91         if (!fread(buf, bdev->bdif->ph_bsize * blk_cnt, 1, dev_file))
  92                 return EIO;
  93
  94         return EOK;
  95 }
  96
  97 static void drop_cache(void)
  98 {
  99 #if defined(__linux__) && DROP_LINUXCACHE_BUFFERS
 100         int fd;
 101         char *data = "3";
 102
 103         sync();
 104         fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
 105         write(fd, data, sizeof(char));
 106         close(fd);
 107 #endif
 108 }
 109
 110 /******************************************************************************/
 111 static int filedev_bwrite(struct ext4_blockdev *bdev, const void *buf,
 112                           uint64_t blk_id, uint32_t blk_cnt)
 113 {
 114         if (fseeko(dev_file, blk_id * bdev->bdif->ph_bsize, SEEK_SET))
 115                 return EIO;
 116         if (!blk_cnt)
 117                 return EOK;
 118         if (!fwrite(buf, bdev->bdif->ph_bsize * blk_cnt, 1, dev_file))
 119                 return EIO;
 120
 121         drop_cache();
 122         return EOK;
 123 }
 124 /******************************************************************************/
 125 static int filedev_close(struct ext4_blockdev *bdev)
 126 {
 127         fclose(dev_file);
 128         return EOK;
 129 }
 130
 131 /******************************************************************************/
 132 struct ext4_blockdev *ext4_filedev_get(void) { return &_filedev; }
 133 /******************************************************************************/
 134 void ext4_filedev_filename(const char *n) { fname = n; }
 135
 136 /******************************************************************************/