Ext2文件系统源代码分析(3)

symlink.c:

/*
 *  linux/fs/ext2/symlink.c
 *
 * Only fast symlinks left here - the rest is done by generic code. AV, 1999
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/symlink.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext2 symlink handling code
 */

#include "ext2.h"
#include "xattr.h"
#include <linux /namei.h>

static void *ext2_follow_link(struct dentry *dentry, struct nameidata *nd)
{
        struct ext2_inode_info *ei = EXT2_I(dentry->d_inode);
        nd_set_link(nd, (char *)ei->i_data);
        return NULL;
}
//ext2_follow_link()函数用于搜索符号连接所在的目标文件

const struct inode_operations ext2_symlink_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = page_follow_link_light,
        .put_link       = page_put_link,
#ifdef CONFIG_EXT2_FS_XATTR
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext2_listxattr,
        .removexattr    = generic_removexattr,
#endif
};
//ext2_symlink_inode_operations定义了上层(VFS)符号连接操作在ext2文件系统这一层中的具体实现函数

const struct inode_operations ext2_fast_symlink_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = ext2_follow_link,
#ifdef CONFIG_EXT2_FS_XATTR
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext2_listxattr,
        .removexattr    = generic_removexattr,
#endif
};
//ext2_fast_symlink_inode_operations应该是为了向下兼容2.4内核使用的符号连接操作函数

fsync.c:

/*
 *  linux/fs/ext2/fsync.c
 *
 *  Copyright (C) 1993  Stephen Tweedie (sct@dcs.ed.ac.uk)
 *  from
 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
 *                      Laboratoire MASI - Institut Blaise Pascal
 *                      Universite Pierre et Marie Curie (Paris VI)
 *  from
 *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
 * 
 *  ext2fs fsync primitive
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 * 
 *  Removed unnecessary code duplication for little endian machines
 *  and excessive __inline__s. 
 *        Andi Kleen, 1997
 *
 * Major simplications and cleanup - we only need to do the metadata, because
 * we can depend on generic_block_fdatasync() to sync the data blocks.
 */

#include "ext2.h"
#include </linux><linux /buffer_head.h>          /* for sync_mapping_buffers() */

/*
 *      File may be NULL when we are called. Perhaps we shouldn't
 *      even pass file to fsync ?
 */

int ext2_sync_file(struct file *file, struct dentry *dentry, int datasync)
{
        struct inode *inode = dentry->d_inode;
        int err;
        int ret;

        ret = sync_mapping_buffers(inode->i_mapping);
        if (!(inode->i_state & I_DIRTY))
                return ret;
        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
                return ret;

        err = ext2_sync_inode(inode);
        if (ret == 0)
                ret = err;
        return ret;
}
//ext2_sync_file函数对文件进行同步，它只检查inode中的脏数据，通过对ext2_sync_inode调用把数据写入硬盘
//sync_mapping_buffers作用是写出地址空间所有间接的blocks