/*
* linux/fs/minix/inode.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#ifdef MODULE
#include <linux/module.h>
#include <linux/version.h>
#else
#define MOD_INC_USE_COUNT
#define MOD_DEC_USE_COUNT
#endif
#include <linux/sched.h>
#include <linux/minix_fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/locks.h>
#include <asm/system.h>
#include <asm/segment.h>
#include <asm/bitops.h>
void minix_put_inode(struct inode *inode)
{
if (inode->i_nlink)
return;
// 文件大小变成0
inode->i_size = 0;
// 删除inode的内容
minix_truncate(inode);
// 释放inode节点,插入空闲队列
minix_free_inode(inode);
}
// 回写超级块内容
static void minix_commit_super (struct super_block * sb,
struct minix_super_block * ms)
{
// sb->u.minix_sb.s_sbh是管理该超级块的buffer
mark_buffer_dirty(sb->u.minix_sb.s_sbh, 1);
sb->s_dirt = 0;
}
// 回写超级块信息到硬盘
void minix_write_super (struct super_block * sb)
{
struct minix_super_block * ms;
// 没有设置只读标记
if (!(sb->s_flags & MS_RDONLY)) {
ms = sb->u.minix_sb.s_ms;
if (ms->s_state & MINIX_VALID_FS)
ms->s_state &= ~MINIX_VALID_FS;
minix_commit_super (sb, ms);
}
sb->s_dirt = 0;
}
// 回写超级块的内容
void minix_put_super(struct super_block *sb)
{
int i;
// 加锁
lock_super(sb);
//
if (!(sb->s_flags & MS_RDONLY)) {
sb->u.minix_sb.s_ms->s_state = sb->u.minix_sb.s_mount_state;
mark_buffer_dirty(sb->u.minix_sb.s_sbh, 1);
}
// 置为0说明没有不在使用
sb->s_dev = 0;
// 回写inode位图信息
for(i = 0 ; i < MINIX_I_MAP_SLOTS ; i++)
brelse(sb->u.minix_sb.s_imap[i]);
// 回写块位图信息
for(i = 0 ; i < MINIX_Z_MAP_SLOTS ; i++)
brelse(sb->u.minix_sb.s_zmap[i]);
// 回写超级块其他字段
brelse (sb->u.minix_sb.s_sbh);
// 解锁
unlock_super(sb);
MOD_DEC_USE_COUNT;
return;
}
static struct super_operations minix_sops = {
minix_read_inode,
NULL,
minix_write_inode,
minix_put_inode,
minix_put_super,
minix_write_super,
minix_statfs,
minix_remount
};
// 重新挂载文件系统,其实只能改变flag,而不是卸载再挂载
int minix_remount (struct super_block * sb, int * flags, char * data)
{
struct minix_super_block * ms;
// s_ms保存的minix文件系统超级块的信息
ms = sb->u.minix_sb.s_ms;
if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
return 0;
if (*flags & MS_RDONLY) {
if (ms->s_state & MINIX_VALID_FS ||
!(sb->u.minix_sb.s_mount_state & MINIX_VALID_FS))
return 0;
/* Mounting a rw partition read-only. */
ms->s_state = sb->u.minix_sb.s_mount_state;
mark_buffer_dirty(sb->u.minix_sb.s_sbh, 1);
sb->s_dirt = 1;
minix_commit_super (sb, ms);
}
else {
/* Mount a partition which is read-only, read-write. */
sb->u.minix_sb.s_mount_state = ms->s_state;
ms->s_state &= ~MINIX_VALID_FS;
mark_buffer_dirty(sb->u.minix_sb.s_sbh, 1);
sb->s_dirt = 1;
if (!(sb->u.minix_sb.s_mount_state & MINIX_VALID_FS))
printk ("MINIX-fs warning: remounting unchecked fs, "
"running fsck is recommended.\n");
else if ((sb->u.minix_sb.s_mount_state & MINIX_ERROR_FS))
printk ("MINIX-fs warning: remounting fs with errors, "
"running fsck is recommended.\n");
}
return 0;
}
// 读超级块
struct super_block *minix_read_super(struct super_block *s,void *data,
int silent)
{
struct buffer_head *bh;
struct minix_super_block *ms;
int i,dev=s->s_dev,block;
if (32 != sizeof (struct minix_inode))
panic("bad i-node size");
MOD_INC_USE_COUNT;
lock_super(s);
set_blocksize(dev, BLOCK_SIZE);
// 读入超级块
if (!(bh = bread(dev,1,BLOCK_SIZE))) {
// 重置为未使用标记
s->s_dev=0;
unlock_super(s);
printk("MINIX-fs: unable to read superblock\n");
MOD_DEC_USE_COUNT;
return NULL;
}
// 转成minix类型的超级块类型
ms = (struct minix_super_block *) bh->b_data;
// s是vfs的通用结构体,minix_sb是存储超级块信息的结构,s_ms是保存minix类型超级块的结构
s->u.minix_sb.s_ms = ms;
// bh是管理该超级块的buffer
s->u.minix_sb.s_sbh = bh;
//
s->u.minix_sb.s_mount_state = ms->s_state;
// 块大小
s->s_blocksize = 1024;
// 右移10位,用于算出第几块
s->s_blocksize_bits = 10;
// inode的个数
s->u.minix_sb.s_ninodes = ms->s_ninodes;
// 文件系统的总块数,包括数据块,保存元数据的块
s->u.minix_sb.s_nzones = ms->s_nzones;
// inode位图块数
s->u.minix_sb.s_imap_blocks = ms->s_imap_blocks;
// 数据块位图块数
s->u.minix_sb.s_zmap_blocks = ms->s_zmap_blocks;
// 第一个数据块在硬盘的块号
s->u.minix_sb.s_firstdatazone = ms->s_firstdatazone;
// 右移s_log_zone_size位得到每块的大小,区别于用于存储数据的块大小
s->u.minix_sb.s_log_zone_size = ms->s_log_zone_size;
// 单文件最大字节数
s->u.minix_sb.s_max_size = ms->s_max_size;
// 文件系统魔数
s->s_magic = ms->s_magic;
// minix系统的版本
if (s->s_magic == MINIX_SUPER_MAGIC) {
// 目录项结构体minix_dir_entry的大小,两个字节存inode号,14个存文件名
s->u.minix_sb.s_dirsize = 16;
// 文件名长度
s->u.minix_sb.s_namelen = 14;
} else if (s->s_magic == MINIX_SUPER_MAGIC2) {
s->u.minix_sb.s_dirsize = 32;
s->u.minix_sb.s_namelen = 30;
} else {
// 魔数不对
s->s_dev = 0;
unlock_super(s);
brelse(bh);
if (!silent)
printk("VFS: Can't find a minix filesystem on dev 0x%04x.\n", dev);
MOD_DEC_USE_COUNT;
return NULL;
}
// 初始化
for (i=0;i < MINIX_I_MAP_SLOTS;i++)
s->u.minix_sb.s_imap[i] = NULL;
for (i=0;i < MINIX_Z_MAP_SLOTS;i++)
s->u.minix_sb.s_zmap[i] = NULL;
block=2;
// 从第二块开始读,第一块保存超级块信息了,第二块起的n块保存块位图、inode位图
for (i=0 ; i < s->u.minix_sb.s_imap_blocks ; i++)
if ((s->u.minix_sb.s_imap[i]=bread(dev,block,BLOCK_SIZE)) != NULL)
block++;
else
break;
for (i=0 ; i < s->u.minix_sb.s_zmap_blocks ; i++)
if ((s->u.minix_sb.s_zmap[i]=bread(dev,block,BLOCK_SIZE)) != NULL)
block++;
else
break;
// 没有全部读成功,报错
if (block != 2+s->u.minix_sb.s_imap_blocks+s->u.minix_sb.s_zmap_blocks) {
for(i=0;i<MINIX_I_MAP_SLOTS;i++)
brelse(s->u.minix_sb.s_imap[i]);
for(i=0;i<MINIX_Z_MAP_SLOTS;i++)
brelse(s->u.minix_sb.s_zmap[i]);
s->s_dev=0;
unlock_super(s);
brelse(bh);
printk("MINIX-fs: bad superblock or unable to read bitmaps\n");
MOD_DEC_USE_COUNT;
return NULL;
}
// 操作系统查找空闲项的时候,成功则返回第几项,失败则返回0,所以第0项不使用。否则返回0无法判断语义
set_bit(0,s->u.minix_sb.s_imap[0]->b_data);
set_bit(0,s->u.minix_sb.s_zmap[0]->b_data);
unlock_super(s);
/* set up enough so that it can read an inode */
s->s_dev = dev;
// 操作超级块的函数集
s->s_op = &minix_sops;
// 获取第MINIX_ROOT_INO即第1个inode(第0个不用),第一个inode是根inode,即文件系统的起点
s->s_mounted = iget(s,MINIX_ROOT_INO);
// 获取失败则报错
if (!s->s_mounted) {
s->s_dev = 0;
brelse(bh);
printk("MINIX-fs: get root inode failed\n");
MOD_DEC_USE_COUNT;
return NULL;
}
if (!(s->s_flags & MS_RDONLY)) {
ms->s_state &= ~MINIX_VALID_FS;
mark_buffer_dirty(bh, 1);
s->s_dirt = 1;
}
if (!(s->u.minix_sb.s_mount_state & MINIX_VALID_FS))
printk ("MINIX-fs: mounting unchecked file system, "
"running fsck is recommended.\n");
else if (s->u.minix_sb.s_mount_state & MINIX_ERROR_FS)
printk ("MINIX-fs: mounting file system with errors, "
"running fsck is recommended.\n");
return s;
}
// 显示minix文件系统的参数,块数、可用数、文件名长度等
void minix_statfs(struct super_block *sb, struct statfs *buf)
{
long tmp;
put_fs_long(MINIX_SUPER_MAGIC, &buf->f_type);
put_fs_long(1024, &buf->f_bsize);
tmp = sb->u.minix_sb.s_nzones - sb->u.minix_sb.s_firstdatazone;
tmp <<= sb->u.minix_sb.s_log_zone_size;
put_fs_long(tmp, &buf->f_blocks);
tmp = minix_count_free_blocks(sb);
put_fs_long(tmp, &buf->f_bfree);
put_fs_long(tmp, &buf->f_bavail);
put_fs_long(sb->u.minix_sb.s_ninodes, &buf->f_files);
put_fs_long(minix_count_free_inodes(sb), &buf->f_ffree);
put_fs_long(sb->u.minix_sb.s_namelen, &buf->f_namelen);
/* Don't know what value to put in buf->f_fsid */
}
// i_data里保存的是文件内容的块号和硬盘块号的对应关系
#define inode_bmap(inode,nr) ((inode)->u.minix_i.i_data[(nr)])
// bh->b_data保存的是文件内容块号和硬盘块号的对应关系
static int block_bmap(struct buffer_head * bh, int nr)
{
int tmp;
if (!bh)
return 0;
tmp = ((unsigned short *) bh->b_data)[nr];
brelse(bh);
return tmp;
}
// 获取文件内容的逻辑块号在硬盘中对应的实际块号
int minix_bmap(struct inode * inode,int block)
{
int i;
if (block<0) {
printk("minix_bmap: block<0");
return 0;
}
if (block >= 7+512+512*512) {
printk("minix_bmap: block>big");
return 0;
}
// 小于7的块号直接存在inode里
if (block < 7)
return inode_bmap(inode,block);
block -= 7;
// inode的i_data的第八个元素保存了一个块号,该块里的内容保存了512个块号,即第8块开始的文件内容
if (block < 512) {
// 先拿到一级块号
i = inode_bmap(inode,7);
if (!i)
return 0;
// 把一级块号对应的数据从硬盘读取进来,然后再根据偏移找到对应的二级块号,即文件内容对应的块号
return block_bmap(bread(inode->i_dev,i,BLOCK_SIZE),block);
}
block -= 512;
/*
inode的i_data的第九个元素保存了一个块号,该块包括了512块号,
512块号每个块号对应的块又保存了512个块号,最后的512块号保存了文件内容的块号
*/
i = inode_bmap(inode,8);
if (!i)
return 0;
// >>9即除以512算出在哪个二级块
i = block_bmap(bread(inode->i_dev,i,BLOCK_SIZE),block>>9);
if (!i)
return 0;
// &511算出偏移
return block_bmap(bread(inode->i_dev,i,BLOCK_SIZE),block & 511);
}
// 读取buffer中某个硬盘数据块对应的内容,create=1,说明没有对应数据块则创建一个
static struct buffer_head * inode_getblk(struct inode * inode, int nr, int create)
{
int tmp;
unsigned short *p;
struct buffer_head * result;
p = inode->u.minix_i.i_data + nr;
repeat:
// 硬盘块号
tmp = *p;
if (tmp) {
// 判断是不是在buffer里。
result = getblk(inode->i_dev, tmp, BLOCK_SIZE);
// 判断p指向块号是不是变了,是的话说明获取的数据result不是对的
if (tmp == *p)
return result;
brelse(result);
goto repeat;
}
// create是0说明不需要新建,等于1即找不到的时候新建一个
if (!create)
return NULL;
// 从硬盘中创建一个新的块
tmp = minix_new_block(inode->i_sb);
if (!tmp)
return NULL;
//
result = getblk(inode->i_dev, tmp, BLOCK_SIZE);
// p非空说明该项被使用了,则释放,可能因为中断引起的
if (*p) {
minix_free_block(inode->i_sb,tmp);
brelse(result);
goto repeat;
}
// 保存映射关系
*p = tmp;
// 创建时间
inode->i_ctime = CURRENT_TIME;
// inode新增了一个映射关系,需要回写到硬盘
inode->i_dirt = 1;
return result;
}
// 读取buffer中硬盘某个块的对应的数据,或者新建一个块,bh->b_data保存了512个文件块号到硬盘块号。逻辑类似上面的函数
static struct buffer_head * block_getblk(struct inode * inode,
struct buffer_head * bh, int nr, int create)
{
int tmp;
unsigned short *p;
struct buffer_head * result;
if (!bh)
return NULL;
// 数据不是最新的,则先刷新缓存的数据
if (!bh->b_uptodate) {
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
if (!bh->b_uptodate) {
brelse(bh);
return NULL;
}
}
p = nr + (unsigned short *) bh->b_data;
repeat:
tmp = *p;
if (tmp) {
result = getblk(bh->b_dev, tmp, BLOCK_SIZE);
if (tmp == *p) {
brelse(bh);
return result;
}
brelse(result);
goto repeat;
}
if (!create) {
brelse(bh);
return NULL;
}
tmp = minix_new_block(inode->i_sb);
if (!tmp) {
brelse(bh);
return NULL;
}
result = getblk(bh->b_dev, tmp, BLOCK_SIZE);
if (*p) {
minix_free_block(inode->i_sb,tmp);
brelse(result);
goto repeat;
}
*p = tmp;
mark_buffer_dirty(bh, 1);
brelse(bh);
return result;
}
/*
获取硬盘某块数据的内容,是对上面两个函数的封装,
主要是计算block的逻辑,inode_getblk,block_getblk是已经知道要获取
的是硬盘的哪个块。minix_getblk是给这两个函数计算出最终的硬盘块号
*/
struct buffer_head * minix_getblk(struct inode * inode, int block, int create)
{
struct buffer_head * bh;
if (block<0) {
printk("minix_getblk: block<0");
return NULL;
}
if (block >= 7+512+512*512) {
printk("minix_getblk: block>big");
return NULL;
}
if (block < 7)
return inode_getblk(inode,block,create);
block -= 7;
if (block < 512) {
bh = inode_getblk(inode,7,create);
return block_getblk(inode, bh, block, create);
}
block -= 512;
bh = inode_getblk(inode,8,create);
bh = block_getblk(inode, bh, block>>9, create);
return block_getblk(inode, bh, block & 511, create);
}
// 读某块内容,先从buffer获取,没有的话再去读取硬盘里的数据
struct buffer_head * minix_bread(struct inode * inode, int block, int create)
{
struct buffer_head * bh;
// 从buffer里读取对应硬盘块的数据
bh = minix_getblk(inode,block,create);
// 失败或者是最新的则返回
if (!bh || bh->b_uptodate)
return bh;
// 获取到但是不是最新的数据则调驱动层去读取最新的
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
// 是最新的则返回
if (bh->b_uptodate)
return bh;
brelse(bh);
return NULL;
}
void minix_read_inode(struct inode * inode)
{
struct buffer_head * bh;
struct minix_inode * raw_inode;
int block, ino;
// inode号
ino = inode->i_ino;
inode->i_op = NULL;
inode->i_mode = 0;
if (!ino || ino >= inode->i_sb->u.minix_sb.s_ninodes) {
printk("Bad inode number on dev 0x%04x: %d is out of range\n",
inode->i_dev, ino);
return;
}
// 文件系统第一块是引导扇区,第二块是超级块,算出inode在硬盘的块号,imap是存储数据块位图相关的信息需要的空大小
block = 2 + inode->i_sb->u.minix_sb.s_imap_blocks +
inode->i_sb->u.minix_sb.s_zmap_blocks +
(ino-1)/MINIX_INODES_PER_BLOCK;
// 把整一块读进来
if (!(bh=bread(inode->i_dev,block, BLOCK_SIZE))) {
printk("Major problem: unable to read inode from dev 0x%04x\n",
inode->i_dev);
return;
}
// 算出inode在该块的块内偏移,得到inode的内容
raw_inode = ((struct minix_inode *) bh->b_data) +
(ino-1)%MINIX_INODES_PER_BLOCK;
// 赋值过去
inode->i_mode = raw_inode->i_mode;
inode->i_uid = raw_inode->i_uid;
inode->i_gid = raw_inode->i_gid;
inode->i_nlink = raw_inode->i_nlinks;
inode->i_size = raw_inode->i_size;
inode->i_mtime = inode->i_atime = inode->i_ctime = raw_inode->i_time;
inode->i_blocks = inode->i_blksize = 0;
// 如果是字符或者块文件,i_zone[0]保存的是设备号
if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
inode->i_rdev = raw_inode->i_zone[0];
// 一般文件i_zone保存的是文件内容的块号
else for (block = 0; block < 9; block++)
inode->u.minix_i.i_data[block] = raw_inode->i_zone[block];
// 用完释放
brelse(bh);
// 根据文件类型赋值对应的操作函数集
if (S_ISREG(inode->i_mode))
inode->i_op = &minix_file_inode_operations;
else if (S_ISDIR(inode->i_mode))
inode->i_op = &minix_dir_inode_operations;
else if (S_ISLNK(inode->i_mode))
inode->i_op = &minix_symlink_inode_operations;
else if (S_ISCHR(inode->i_mode))
inode->i_op = &chrdev_inode_operations;
else if (S_ISBLK(inode->i_mode))
inode->i_op = &blkdev_inode_operations;
else if (S_ISFIFO(inode->i_mode))
init_fifo(inode);
}
static struct buffer_head * minix_update_inode(struct inode * inode)
{
struct buffer_head * bh;
struct minix_inode * raw_inode;
int ino, block;
ino = inode->i_ino;
if (!ino || ino >= inode->i_sb->u.minix_sb.s_ninodes) {
printk("Bad inode number on dev 0x%04x: %d is out of range\n",
inode->i_dev, ino);
inode->i_dirt = 0;
return 0;
}
// 算出inode在硬盘哪个数据块,s_imap_blocks和s_zmap_blocks是数据位图和inode位图的块数
block = 2 + inode->i_sb->u.minix_sb.s_imap_blocks + inode->i_sb->u.minix_sb.s_zmap_blocks +
(ino-1)/MINIX_INODES_PER_BLOCK;
if (!(bh=bread(inode->i_dev, block, BLOCK_SIZE))) {
printk("unable to read i-node block\n");
inode->i_dirt = 0;
return 0;
}
// 算出inode在这个数据块的偏移
raw_inode = ((struct minix_inode *)bh->b_data) +
(ino-1)%MINIX_INODES_PER_BLOCK;
raw_inode->i_mode = inode->i_mode;
raw_inode->i_uid = inode->i_uid;
raw_inode->i_gid = inode->i_gid;
raw_inode->i_nlinks = inode->i_nlink;
raw_inode->i_size = inode->i_size;
raw_inode->i_time = inode->i_mtime;
if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
raw_inode->i_zone[0] = inode->i_rdev;
else for (block = 0; block < 9; block++)
raw_inode->i_zone[block] = inode->u.minix_i.i_data[block];
inode->i_dirt=0;
// 回写inode内容到硬盘,上面的代码见read_inode注释
mark_buffer_dirty(bh, 1);
return bh;
}
void minix_write_inode(struct inode * inode)
{
struct buffer_head *bh;
bh = minix_update_inode(inode);
brelse(bh);
}
// 回写inode到硬盘
int minix_sync_inode(struct inode * inode)
{
int err = 0;
struct buffer_head *bh;
// 回写
bh = minix_update_inode(inode);
// 上面的回写是等待线程定期回写的,失败的话自己调驱动层直接回写
if (bh && bh->b_dirt)
{
// 驱动层会锁住buffer
ll_rw_block(WRITE, 1, &bh);
wait_on_buffer(bh);
if (bh->b_req && !bh->b_uptodate)
{
printk ("IO error syncing minix inode [%04x:%08lx]\n",
inode->i_dev, inode->i_ino);
err = -1;
}
}
else if (!bh)
err = -1;
brelse (bh);
return err;
}
#ifdef MODULE
char kernel_version[] = UTS_RELEASE;
static struct file_system_type minix_fs_type = {
minix_read_super, "minix", 1, NULL
};
// 支持以模块加载
int init_module(void)
{
// 注册文件系统
register_filesystem(&minix_fs_type);
return 0;
}
// 卸载模块
void cleanup_module(void)
{
unregister_filesystem(&minix_fs_type);
}
#endif