📄 042_fs_file_c.html

📁 重读linux 2.4.2o所写的笔记
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      <pre>2007-12-19   <br><br>这是一个比较简单的模块,从open.c中copy出来的.先看看task_struct 里有关文件的几个控制结构吧.<br>struct <font color=#000099><b>task_struct</b></font> {<br>        ........ 	<br>/* task state */<br>	struct linux_binfmt *binfmt; <font color=#3333ff>/*elf aout ....*/</font><br>	.....<br>	int dumpable:1;<font color=#3333ff> /*是否可以core dump*/</font><br>/* limits */<br>	char comm[16]; <font color=#3333ff> /*core dump的名称(可执行文件名)*/</font><br>/* file system info */<br>        ...<br>	unsigned int locks; <font color=#3333ff>/* How many file locks are being held */</font><br>/* filesystem information */<br>	struct fs_struct *<font color=#000099><b>fs</b></font>;<br>/* open file information */<br>	struct <font color=#006600><b>files_struct</b></font> *<font color=#000099><b>files</b></font>;<br>        .....<br>};<br>struct <font color=#009900><b>files_struct</b></font> {<br>	atomic_t count;<br>	rwlock_t file_lock;<br>	int max_fds;<br>	int max_fdset;<br>	int next_fd;<br>	<font color=#006600>struct file ** <b>fd</b></font>;	/* current fd array,init is fd_arrary */<br>	fd_set *<b>close_on_exec</b>;<br>	fd_set *<b>open_fds</b>; /*bitmap for open fd_array*/<br>	fd_set <font color=#000099><b>close_on_exec_init</b></font>;<br>	fd_set open_fds_init;<br>	struct file * <font color=#006600><b>fd_array</b></font>[NR_OPEN_DEFAULT]; /*inline的fd array*/<br>};<br><br>这里只关心files_struct. file_struct含有两个fd_set一个fd array(黑体和绿体字). 已开始fd指向fd_array,见<br>static int <font color=#000099><b>copy_files</b></font>(unsigned long clone_flags, struct task_struct * tsk)<br>{<br>	.....<br>	newf-&gt;close_on_exec = &amp;newf-&gt;close_on_exec_init;<br>	newf-&gt;open_fds	    = &amp;newf-&gt;open_fds_init;<br>	newf-&gt;fd	    = &amp;newf-&gt;fd_array[0];<br>        ...<br>}<br><br>之后需要扩展的时候.... 就是这个模块的事情了.<br>struct file ** <font color=#000099><b>alloc_fd_array</b></font>(int num)<br>void <font color=#000099><b>free_fd_array</b></font>(struct file **array, int num)<br>int <font color=#000099><b>expand_fd_array</b></font>(struct files_struct *files, int nr)<br>fd_set * <font color=#000099><b>alloc_fdset</b></font>(int num)<br>void <font color=#000099><b>free_fdset</b></font>(fd_set *array, int num)<br>int <font color=#000099><b>expand_fdset</b></font>(struct files_struct *files, int nr)<br><br>自己觉得没有必要每个函数分析了,就这四个函数....<br></pre>
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