linux-0.11调试教程，mkfs.c源代码分析（3）

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如果mkfs命令加-c选项会执行check_blocks()函数当然会很费时。大约2分钟。

check_blocks()函数通过逐个读取块的内容，如果不能读取，算出哪个块不能读取，既是坏块，计算出坏块的块号既current_block，然后把对应的逻辑块位图中的位置位，表示已经损坏，在make_bad_inode()函数运行的时候会根据逻辑块位图中的位是否被置1换算成坏块的块号放到坏块文件中的i_zone[]中。

void check_blocks(void)

{
   unsigned int current_block=0;
   int try,got;
   static char buffer[BLOCK_SIZE * TEST_BUFFER_BLOCKS];

   while (current_block < ZONES) {
       if (lseek(DEV,current_block*BLOCK_SIZE,SEEK_SET) !=
       current_block*BLOCK_SIZE)
           die("seek failed in check_blocks");
       try = TEST_BUFFER_BLOCKS;
       if (current_block + try > ZONES)
           try = ZONES-current_block;
       got = read(DEV, buffer, try * BLOCK_SIZE);
       if (got<0)
           got = 0;
       if (got & (BLOCK_SIZE-1))
           printf("Weird values in check_blocks: probably bugs\n");
       got /= BLOCK_SIZE;
       current_block += got;
       if (got == try)
           continue;
       if (current_block < FIRSTZONE)
           die("bad blocks before data-area: cannot make fs");
       mark_zone(current_block);
       badblocks++;
       current_block++;
   }
   if (badblocks)
       printf("%d bad block%s\n",badblocks,(badblocks>1)?"s":"");
}

write_tables()函数把超级块和i节点位图块和逻辑块位图块和i节点缓存写到设备中。

void write_tables(void)
{
   if (BLOCK_SIZE != lseek(DEV, BLOCK_SIZE, SEEK_SET))
       die("seek failed in write_tables");
   if (BLOCK_SIZE != write(DEV, super_block_buffer, BLOCK_SIZE))
       die("unable to write super-block");
   if (IMAPS*BLOCK_SIZE != write(DEV,inode_map,IMAPS*BLOCK_SIZE))
       die("Unable to write inode map");
   if (ZMAPS*BLOCK_SIZE != write(DEV,zone_map,ZMAPS*BLOCK_SIZE))
       die("Unable to write zone map");
   if (INODE_BUFFER_SIZE != write(DEV,inode_buffer,INODE_BUFFER_SIZE))
       die("Unable to write inodes");
}