Linux内核的ext4文件系统对其代码逐行逐行注释介绍

Linux内核的ext4文件系统是一种高性能、可靠的文件系统，它是Linux操作系统中最常用的文件系统之一。下面我们来逐行逐行注释介绍它的代码。

/*
 *  linux/fs/ext4/super.c
 *
 *  Copyright (C) 2001-2008 Jan Kara
 *
 *  This file contains ext4 filesystem superblock operations
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software Foundation,
 *  Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

这是文件的头部，包括版权声明和一些说明。

#include "ext4.h"

包含了ext4文件系统的头文件。

static int ext4_show_options(struct seq_file *seq, struct dentry *root)
{
    struct super_block *sb = root->d_sb;
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    unsigned long flags;

    /* ... */
}

这个函数用于显示文件系统的挂载参数。其中，struct seq_file是内核序列文件的数据结构，struct dentry是一个目录项的数据结构，struct super_block是超级块的数据结构，struct ext4_sb_info是ext4文件系统的特有数据结构，用于存储文件系统的相关信息。unsigned long是一个无符号的长整型。

static const match_table_t tokens = {
    {Opt_journal_dev, "journal_dev=%s"},
    {Opt_journal_path, "journal_path=%s"},
    {Opt_journal_check_interval, "journal_check_interval=%s"},
    {Opt_max_batch_time, "max_batch_time=%s"},
    {Opt_stripe, "stripe=%s"},
    {Opt_delalloc, "delalloc"},
    {Opt_nodelalloc, "nodelalloc"},
    {Opt_barrier, "barrier=%s"},
    {Opt_nobarrier, "nobarrier"},
    {Opt_err, NULL}
};

这个数据结构定义了文件系统的挂载参数和对应的字符串。

static int parse_options(char *options, struct super_block *sb,
              struct ext4_mount_options *parsed)
{
    char *p;
    substring_t args[MAX_OPT_ARGS];
    int option;
    int token;
    int err = 0;

    /* ... */
}

这个函数用于解析文件系统的挂载参数。其中，parsed是一个结构体，用于存储解析后的参数。

static int ext4_fill_super(struct super_block *sb, void *data, int silent)
{
    struct buffer_head *bh;
    struct ext4_super_block *es;
    struct ext4_sb_info *sbi;
    struct inode *root;
    int blocksize;
    int db_count;
    unsigned long long tmp;

    /* ... */
}

这个函数用于填充文件系统的超级块。其中，struct buffer_head是缓冲头的数据结构，struct ext4_super_block是ext4文件系统的超级块数据结构，struct inode是一个inode节点的数据结构，unsigned long long是一个无符号的长长整型。