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<a name='TOP'><h2><a href='../mains.html'>root</a>/<a href='../files/98.html'>fs</a>/bitmap.c</h2>
<i><font color='green'>/* [<][>]<a href='#L59'>[^]</a><a href='#L185'>[v]</a>[top]<a href='#BOTTOM'>[bottom]</a><a href='../mains.html'>[index]</a><a href='../help.html'>[help]</a> */</font></i>
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<h2>DEFINITIONS</h2>
This source file includes following definitions.
<ol>
<li><a href='#L59' title='Defined at 59.'>free_block</a>
<li><a href='#L99' title='Defined at 99.'>new_block</a>
<li><a href='#L143' title='Defined at 143.'>free_inode</a>
<li><a href='#L185' title='Defined at 185.'>new_inode</a>
</ol>
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<pre>
<a name='L1'><i><font color='green'>/*</font></i>
<a name='L2'><i><font color='green'>* linux/fs/bitmap.c</font></i>
<a name='L3'><i><font color='green'>*</font></i>
<a name='L4'><i><font color='green'>* (C) 1991 Linus Torvalds</font></i>
<a name='L5'><i><font color='green'>*/</font></i>
<a name='L6'>
<a name='L7'><i><font color='green'>/* bitmap.c contains the code that handles the inode and block bitmaps */</font></i>
<a name='L8'><i><font color='green'>/* bitmap.c 程序含有处理i 节点和磁盘块位图的代码 */</font></i>
<a name='L9'><font color='darkred'>#include</font> <<a href='42.html'>string.h</a>> <i><font color='green'>// 字符串头文件。主要定义了一些有关字符串操作的嵌入函数。</font></i>
<a name='L10'><i><font color='green'>// 主要使用了其中的memset()函数。</font></i>
<a name='L11'><font color='darkred'>#include</font> <<a href='36.html'>linux/sched.h</a>> <i><font color='green'>// 调度程序头文件，定义了任务结构task_struct、初始任务0 的数据，</font></i>
<a name='L12'><i><font color='green'>// 还有一些有关描述符参数设置和获取的嵌入式汇编函数宏语句。</font></i>
<a name='L13'><font color='darkred'>#include</font> <<a href='34.html'>linux/kernel.h</a>> <i><font color='green'>// 内核头文件。含有一些内核常用函数的原形定义。</font></i>
<a name='L14'>
<a name='L15'><i><font color='green'>//// 将指定地址(addr)处的一块内存清零。嵌入汇编程序宏。</font></i>
<a name='L16'><i><font color='green'>// 输入：eax = 0，ecx = 数据块大小BLOCK_SIZE/4，edi = addr。</font></i>
<a name='L17'><font color='darkred'>#define</font> <a href='../S/4.html#L134' title='Refered from 134 in fs/bitmap.c.'>clear_block</a>(addr) \
<a name='L18'><b>__asm__</b>( "cld\n\t" \ <i><font color='green'>// 清方向位。</font></i>
<a name='L19'>"rep\n\t" \ <i><font color='green'>// 重复执行存储数据（0）。</font></i>
<a name='L20'>"stosl"::"a" (0), "c" (<a href='../D/23.html' title='Multiple defined in 2 places.'>BLOCK_SIZE</a> / 4), "D" ((<b>long</b>) (addr)):"cx", "di")
<a name='L21'><i><font color='green'>//// 置位指定地址开始的第nr 个位偏移处的比特位(nr 可以大于32！)。返回原比特位（0 或1）。</font></i>
<a name='L22'><i><font color='green'>// 输入：%0 - eax（返回值)，%1 - eax(0)；%2 - nr，位偏移值；%3 - (addr)，addr 的内容。</font></i>
<a name='L23'><font color='darkred'>#define</font> <a href='../R/593.html' title='Multiple refered from 4 places.'>set_bit</a>(nr,addr) (<font color='red'>{</font>\
<a name='L24'><b>register</b> <b>int</b> res <b>__asm__</b>( "ax"); \
<a name='L25'><b>__asm__</b> <b>__volatile__</b>( "btsl %2,%3\n\tsetb %%al": \
<a name='L26'>"=a" (res): "" (0), "r" (nr), "m" (*(addr))); \
<a name='L27'>res;<font color='red'>}</font>)
<a name='L28'><i><font color='green'>//// 复位指定地址开始的第nr 位偏移处的比特位。返回原比特位的反码（1 或0）。</font></i>
<a name='L29'><i><font color='green'>// 输入：%0 - eax（返回值)，%1 - eax(0)；%2 - nr，位偏移值；%3 - (addr)，addr 的内容。</font></i>
<a name='L30'><font color='darkred'>#define</font> <a href='../R/400.html' title='Multiple refered from 2 places.'>clear_bit</a>(nr,addr) (<font color='red'>{</font>\
<a name='L31'><b>register</b> <b>int</b> res <b>__asm__</b>( "ax"); \
<a name='L32'><b>__asm__</b> <b>__volatile__</b>( "btrl %2,%3\n\tsetnb %%al": \
<a name='L33'>"=a" (res): "" (0), "r" (nr), "m" (*(addr))); \
<a name='L34'>res;<font color='red'>}</font>)
<a name='L35'><i><font color='green'>//// 从addr 开始寻找第1 个0 值比特位。</font></i>
<a name='L36'><i><font color='green'>// 输入：%0 - ecx(返回值)；%1 - ecx(0)；%2 - esi(addr)。</font></i>
<a name='L37'><i><font color='green'>// 在addr 指定地址开始的位图中寻找第1 个是0 的比特位，并将其距离addr 的比特位偏移值返回。</font></i>
<a name='L38'><font color='darkred'>#define</font> <a href='../R/455.html' title='Multiple refered from 2 places.'>find_first_zero</a>(addr) (<font color='red'>{</font> \
<a name='L39'><b>int</b> __res; \
<a name='L40'><b>__asm__</b>( "cld\n" \ <i><font color='green'>// 清方向位。</font></i>
<a name='L41'> "1:\tlodsl\n\t" \ <i><font color='green'>// 取[esi]??eax。</font></i>
<a name='L42'> "notl %%eax\n\t" \ <i><font color='green'>// eax 中每位取反。</font></i>
<a name='L43'> "bsfl %%eax,%%edx\n\t" \ <i><font color='green'>// 从位0 扫描eax 中是1 的第1 个位，其偏移值??edx。</font></i>
<a name='L44'> "je 2f\n\t" \ <i><font color='green'>// 如果eax 中全是0，则向前跳转到标号2 处(40 行)。</font></i>
<a name='L45'> "addl %%edx,%%ecx\n\t" \ <i><font color='green'>// 偏移值加入ecx(ecx 中是位图中首个是0 的比特位的偏移值)</font></i>
<a name='L46'> "jmp 3f\n" \ <i><font color='green'>// 向前跳转到标号3 处（结束）。</font></i>
<a name='L47'> "2:\taddl $32,%%ecx\n\t" \ <i><font color='green'>// 没有找到0 比特位，则将ecx 加上1 个长字的位偏移量32。</font></i>
<a name='L48'> "cmpl $8192,%%ecx\n\t" \ <i><font color='green'>// 已经扫描了8192 位（1024 字节）了吗？</font></i>
<a name='L49'> "jl 1b\n" \ <i><font color='green'>// 若还没有扫描完1 块数据，则向前跳转到标号1 处，继续。</font></i>
<a name='L50'> "3:" \ <i><font color='green'>// 结束。此时ecx 中是位偏移量。</font></i>
<a name='L51'>: "=c" (__res): "c" (0), "S" (addr):"ax", "dx", "si");
<a name='L52'>__res;
<a name='L53'><font color='red'>}</font>
<a name='L54'>
<a name='L55'>)
<a name='L56'><i><font color='green'>//// 释放设备dev 上数据区中的逻辑块block。</font></i>
<a name='L57'><i><font color='green'>// 复位指定逻辑块block 的逻辑块位图比特位。</font></i>
<a name='L58'><i><font color='green'>// 参数：dev 是设备号，block 是逻辑块号（盘块号）。</font></i>
<a name='L59'> <b>void</b> <a href='../R/464.html' title='Multiple refered from 7 places.'>free_block</a> (<b>int</b> dev, <b>int</b> block)
<a name='L60'> <font color='red'>{</font>
<a name='L61'> <b>struct</b> super_block *sb;
<a name='L62'> <b>struct</b> buffer_head *bh;
<a name='L63'>
<a name='L64'><i><font color='green'>// 取指定设备dev 的超级块，如果指定设备不存在，则出错死机。</font></i>
<a name='L65'> <b>if</b> (!(sb = <a href='../S/19.html#L76' title='Defined at 76 in fs/super.c.'>get_super</a> (<a href='../S/7.html#L136' title='Defined at 136 in fs/char_dev.c.'>dev</a>)))
<a name='L66'> <a href='../S/72.html#L24' title='Defined at 24 in kernel/panic.c.'>panic</a> ("trying to free block on nonexistent device");
<a name='L67'><i><font color='green'>// 若逻辑块号小于首个逻辑块号或者大于设备上总逻辑块数，则出错，死机。</font></i>
<a name='L68'> <b>if</b> (block < sb->s_firstdatazone || block >= sb->s_nzones)
<a name='L69'> <a href='../S/72.html#L24' title='Defined at 24 in kernel/panic.c.'>panic</a> ("trying to free block not in datazone");
<a name='L70'><i><font color='green'>// 从hash 表中寻找该块数据。若找到了则判断其有效性，并清已修改和更新标志，释放该数据块。</font></i>
<a name='L71'><i><font color='green'>// 该段代码的主要用途是如果该逻辑块当前存在于高速缓冲中，就释放对应的缓冲块。</font></i>
<a name='L72'> bh = <a href='../S/6.html#L261' title='Defined at 261 in fs/buffer.c.'>get_hash_table</a> (<a href='../S/7.html#L136' title='Defined at 136 in fs/char_dev.c.'>dev</a>, block);
<a name='L73'> <b>if</b> (bh)
<a name='L74'> <font color='red'>{</font>
<a name='L75'> <b>if</b> (bh->b_count != 1)
<a name='L76'> <font color='red'>{</font>
<a name='L77'> <a href='../S/73.html#L30' title='Defined at 30 in kernel/printk.c.'>printk</a> ("trying to free block (%04x:%d), count=%d\n",
<a name='L78'> <a href='../S/7.html#L136' title='Defined at 136 in fs/char_dev.c.'>dev</a>, block, bh->b_count);
<a name='L79'> <b>return</b>;
<a name='L80'> <font color='red'>}</font>
<a name='L81'> bh->b_dirt = 0; <i><font color='green'>// 复位脏（已修改）标志位。</font></i>
<a name='L82'> bh->b_uptodate = 0; <i><font color='green'>// 复位更新标志。</font></i>
<a name='L83'> <a href='../S/6.html#L377' title='Defined at 377 in fs/buffer.c.'>brelse</a> (bh);
<a name='L84'> <font color='red'>}</font>
<a name='L85'><i><font color='green'>// 计算block 在数据区开始算起的数据逻辑块号（从1 开始计数）。然后对逻辑块(区块)位图进行操作，</font></i>
<a name='L86'><i><font color='green'>// 复位对应的比特位。若对应比特位原来即是0，则出错，死机。</font></i>
<a name='L87'> block -= sb->s_firstdatazone - 1; <i><font color='green'>// block = block - ( -1) ;</font></i>
<a name='L88'> <b>if</b> (<a href='../S/4.html#L30' title='Defined at 30 in fs/bitmap.c.'>clear_bit</a> (block & 8191, sb->s_zmap[block / 8192]->b_data))
<a name='L89'> <font color='red'>{</font>
<a name='L90'> <a href='../S/73.html#L30' title='Defined at 30 in kernel/printk.c.'>printk</a> ("block (%04x:%d) ", <a href='../S/7.html#L136' title='Defined at 136 in fs/char_dev.c.'>dev</a>, block + sb->s_firstdatazone - 1);
<a name='L91'> <a href='../S/72.html#L24' title='Defined at 24 in kernel/panic.c.'>panic</a> ("free_block: bit already cleared");
<a name='L92'> <font color='red'>}</font>
<a name='L93'><i><font color='green'>// 置相应逻辑块位图所在缓冲区已修改标志。</font></i>
<a name='L94'> sb->s_zmap[block / 8192]->b_dirt = 1;
<a name='L95'> <font color='red'>}</font>
<a name='L96'>
<a name='L97'><i><font color='green'>////向设备dev 申请一个逻辑块（盘块，区块）。返回逻辑块号（盘块号）。</font></i>
<a name='L98'><i><font color='green'>// 置位指定逻辑块block 的逻辑块位图比特位。</font></i>
<a name='L99'><b>int</b> <a href='../R/535.html' title='Multiple refered from 8 places.'>new_block</a> (<b>int</b> dev)
<a name='L100'><font color='red'>{</font>
<a name='L101'> <b>struct</b> buffer_head *bh;
<a name='L102'> <b>struct</b> super_block *sb;
<a name='L103'> <b>int</b> <a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>, j;
<a name='L104'>
<a name='L105'><i><font color='green'>// 从设备dev 取超级块，如果指定设备不存在，则出错死机。</font></i>
<a name='L106'> <b>if</b> (!(sb = <a href='../S/19.html#L76' title='Defined at 76 in fs/super.c.'>get_super</a> (<a href='../S/7.html#L136' title='Defined at 136 in fs/char_dev.c.'>dev</a>)))
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