truncate.c ( File view )

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			/*
* linux/fs/truncate.c
*
* (C) 1991 Linus Torvalds
*/

#include <linux/sched.h>	// 调度程序头文件,定义了任务结构task_struct、初始任务0 的数据,
// 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。

#include <sys/stat.h>		// 文件状态头文件。含有文件或文件系统状态结构stat{

}和常量。

//// 释放一次间接块。
static void
free_ind (int dev, int block)
{

  struct buffer_head *bh;
  unsigned short *p;
  int i;

// 如果逻辑块号为0,则返回。
  if (!block)
    return;
// 读取一次间接块,并释放其上表明使用的所有逻辑块,然后释放该一次间接块的缓冲区。
  if (bh = bread (dev, block))
    {

      p = (unsigned short *) bh->b_data;	// 指向数据缓冲区。
      for (i = 0; i < 512; i++, p++)	// 每个逻辑块上可有512 个块号。
	if (*p)
	  free_block (dev, *p);	// 释放指定的逻辑块。
      brelse (bh);		// 释放缓冲区。
    
}
//其它字段
//i_zone[0]
//i_zone[1]
//i_zone[2]
//i_zone[3]
//i_zone[4]
//i_zone[5]
//i_zone[6]
//i 节点
//直接块号
//一次间接块
//二次间接块
//的一级块
//二次间接块
//的二级块
//一次间接块号
//二次间接块号
//i_zone[7]
//i_zone[8]
// 释放设备上的一次间接块。
  free_block (dev, block);

}

//// 释放二次间接块。
static void
free_dind (int dev, int block)
{

  struct buffer_head *bh;
  unsigned short *p;
  int i;

// 如果逻辑块号为0,则返回。
  if (!block)
    return;
// 读取二次间接块的一级块,并释放其上表明使用的所有逻辑块,然后释放该一级块的缓冲区。
  if (bh = bread (dev, block))
    {

      p = (unsigned short *) bh->b_data;	// 指向数据缓冲区。
      for (i = 0; i < 512; i++, p++)	// 每个逻辑块上可连接512 个二级块。
	if (*p)
	  free_ind (dev, *p);	// 释放所有一次间接块。
      brelse (bh);		// 释放缓冲区。
    
}
// 最后释放设备上的二次间接块。
  free_block (dev, block);

}

//// 将节点对应的文件长度截为0,并释放占用的设备空间。
void
truncate (struct m_inode *inode)
{

  int i;

// 如果不是常规文件或者是目录文件,则返回。
  if (!(S_ISREG (inode->i_mode) || S_ISDIR (inode->i_mode)))
    return;
// 释放i 节点的7 个直接逻辑块,并将这7 个逻辑块项全置零。
  for (i = 0; i < 7; i++)
    if (inode->i_zone[i])
      {
				// 如果块号不为0,则释放之。
	free_block (inode->i_dev, inode->i_zone[i]);
	inode->i_zone[i] = 0;
      
}
  free_ind (inode->i_dev, inode->i_zone[7]);	// 释放一次间接块。
  free_dind (inode->i_dev, inode->i_zone[8]);	// 释放二次间接块。
  inode->i_zone[7] = inode->i_zone[8] = 0;	// 逻辑块项7、8 置零。
  inode->i_size = 0;		// 文件大小置零。
  inode->i_dirt = 1;		// 置节点已修改标志。
  inode->i_mtime = inode->i_ctime = CURRENT_TIME;	// 重置文件和节点修改时间为当前时间。

}
			
...
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Name Size Date
linux0.00 B0% 04-10-07
<boot>0.00 B04-10-07 15:01
bootsect.s12.49 kB08-01-04 21:38
head.s13.22 kB08-01-04 21:38
setup.s12.42 kB08-01-04 21:38
<fs>0.00 B04-10-07 15:01
bitmap.c8.46 kB02-09-04 13:12
block_dev.c3.95 kB02-09-04 13:12
buffer.c17.71 kB02-09-04 13:12
char_dev.c4.09 kB02-09-04 13:12
exec.c18.90 kB02-09-04 13:12
fcntl.c3.33 kB02-09-04 13:12
file_dev.c4.82 kB02-09-04 13:12
file_table.c209.00 B02-09-04 13:12
inode.c14.92 kB02-09-04 13:12
ioctl.c1.94 kB02-09-04 13:12
Makefile6.80 kB08-01-04 21:45
namei.c37.20 kB02-09-04 13:12
open.c10.00 kB02-09-04 13:12
pipe.c5.42 kB02-09-04 13:12
read_write.c5.86 kB02-09-04 13:12
stat.c2.69 kB02-09-04 13:12
super.c13.57 kB02-09-04 13:12
truncate.c2.46 kB02-09-04 13:12
<include>0.00 B04-10-07 15:01
a.out.h8.22 kB02-09-04 13:14
<asm>0.00 B04-10-07 15:01
io.h772.00 B02-09-04 13:14
memory.h1.03 kB08-01-04 22:13
segment.h2.50 kB02-09-04 13:14
system.h4.08 kB02-09-04 13:14
const.h589.00 B02-09-04 13:14
ctype.h1.68 kB02-09-04 13:14
errno.h2.30 kB02-09-04 13:14
fcntl.h3.30 kB02-09-04 13:14
<linux>0.00 B04-10-07 15:01
config.h2.16 kB02-09-04 13:14
fs.h9.72 kB02-09-04 13:14
hdreg.h2.94 kB02-09-04 13:14
head.h760.00 B02-09-04 13:14
kernel.h1.44 kB02-09-04 13:14
mm.h473.00 B02-09-04 13:14
sched.h13.25 kB02-09-04 13:14
sys.h5.41 kB02-09-04 13:14
tty.h3.93 kB02-09-04 13:14
signal.h4.01 kB02-09-04 13:14
stdarg.h1.77 kB02-09-04 13:14
stddef.h378.00 B02-09-04 13:14
string.h21.75 kB02-09-04 13:14
<sys>0.00 B04-10-07 15:01
stat.h2.37 kB02-09-04 13:14
times.h377.00 B02-09-04 13:14
types.h1.10 kB02-09-04 13:14
utsname.h423.00 B02-09-04 13:14
wait.h1.48 kB02-09-04 13:14
termios.h13.58 kB02-09-04 13:14
time.h1.81 kB02-09-04 13:14
unistd.h9.21 kB02-09-04 13:14
utime.h392.00 B02-09-04 13:14
<init>0.00 B04-10-07 15:01
main.c12.52 kB02-09-04 13:12
<kernel>0.00 B04-10-07 15:01
asm.s5.10 kB08-01-04 22:48
<blk_drv>0.00 B04-10-07 15:01
blk.h5.69 kB02-09-04 13:14
floppy.c23.49 kB02-09-04 13:12
hd.c17.14 kB02-09-04 13:12
ll_rw_blk.c7.59 kB02-09-04 13:12
Makefile4.25 kB08-01-04 22:53
ramdisk.c6.13 kB02-09-04 13:12
<chr_drv>0.00 B04-10-07 15:01
console.c30.91 kB02-09-04 13:12
keyboard.S21.04 kB08-01-04 22:59
Makefile4.81 kB08-01-04 22:59
rs_io.s5.75 kB08-01-04 22:59
serial.c2.91 kB02-09-04 13:12
tty_io.c18.40 kB02-09-04 13:12
tty_ioctl.c10.70 kB02-09-04 13:12
exit.c8.08 kB02-09-04 13:12
fork.c6.78 kB15-07-07 22:10
<math>0.00 B04-10-07 15:01
Makefile3.21 kB08-01-04 23:01
math_emulate.c2.08 kB02-09-04 13:12
mktime.c2.72 kB02-09-04 13:12
panic.c952.00 B02-09-04 13:12
printk.c1.75 kB02-09-04 13:12
sched.c18.57 kB16-07-07 21:23
signal.c5.61 kB02-09-04 13:12
sys.c7.62 kB02-09-04 13:12
system_call.s12.53 kB08-01-04 22:48
traps.c8.29 kB04-10-07 14:57
vsprintf.c9.96 kB02-09-04 13:12
<lib>0.00 B04-10-07 15:01
close.c397.00 B02-09-04 13:12
ctype.c1.72 kB02-09-04 13:12
dup.c401.00 B02-09-04 13:12
errno.c66.00 B02-09-04 13:12
execve.c607.00 B02-09-04 13:12
Makefile4.83 kB08-01-04 22:30
malloc.c13.50 kB02-09-04 13:12
open.c1.22 kB02-09-04 13:12
setsid.c382.00 B02-09-04 13:12
string.c199.00 B02-09-04 13:12
wait.c774.00 B02-09-04 13:12
write.c545.00 B02-09-04 13:12
_exit.c616.00 B02-09-04 13:12
Makefile8.58 kB08-01-04 22:21
<mm>0.00 B04-10-07 15:01
Makefile2.91 kB08-01-04 22:34
memory.c25.10 kB02-09-04 13:12
page.s842.00 B08-01-04 22:34
<tools>0.00 B04-10-07 15:01
build.c8.12 kB02-09-04 13:12
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