<Linux kernel development>Chap12 虚拟文件系统VFS

    struct super_block {
        struct list_head s_list; /* list of all superblocks */
        dev_t s_dev; /* identifier */
        unsigned long s_blocksize; /* block size in bytes */
        unsigned long s_old_blocksize; /* old block size in bytes */
        unsigned char s_blocksize_bits; /* block size in bits */
        unsigned char s_dirt; /* dirty flag */
        unsigned long long s_maxbytes; /* max file size */
        struct file_system_type s_type; /* filesystem type */
        struct super_operations s_op; /* superblock methods */
        struct dquot_operations *dq_op; /* quota methods */
        struct quotactl_ops *s_qcop; /* quota control methods */
        struct export_operations *s_export_op; /* export methods */
        unsigned long s_flags; /* mount flags */
        unsigned long s_magic; /* filesystem's magic number */
        struct dentry *s_root; /* directory mount point */
        struct rw_semaphore s_umount; /* unmount semaphore */
        struct semaphore s_lock; /* superblock semaphore */
        int s_count; /* superblock ref count */
        int s_syncing; /* filesystem syncing flag */
        int s_need_sync_fs; /* not-yet-synced flag */
        atomic_t s_active; /* active reference count */
        void *s_security; /* security module */
        struct list_head s_dirty; /* list of dirty inodes */
        struct list_head s_io; /* list of writebacks */
        struct hlist_head s_anon; /* anonymous dentries */
        struct list_head s_files; /* list of assigned files */
        struct block_device *s_bdev; /* associated block device */
        struct list_head s_instances; /* instances of this fs */
        struct quota_info s_dquot; /* quota-specific options */
        char s_id[32]; /* text name */
        void *s_fs_info; /* filesystem-specific info */
        struct semaphore s_vfs_rename_sem; /* rename semaphore */
};

    struct super_operations {
        struct inode *(*alloc_inode) (struct super_block *sb);//在给定的超级块下创建并初始化一个新的索引节点

        void (*destroy_inode) (struct inode *);//释放索引节点

        void (*read_inode) (struct inode *);//以inode->i_ino为索引，从磁盘上读取索引节点

        void (*dirty_inode) (struct inode *);//在索引节点被修改时调用

        void (*write_inode) (struct inode *, int);//将索引节点写入磁盘，int wait参数指明写操作是否要同步

        void (*put_inode) (struct inode *);//释放给定的索引节点

        void (*drop_inode) (struct inode *);//在最后一个指向索引节点的引用被释放胡，VFS调用此函数

        void (*delete_inode) (struct inode *);//从磁盘上删除索引节点

        void (*put_super) (struct super_block *);//卸载文件系统时使用，释放超级块

        void (*write_super) (struct super_block *);//更新磁盘上的超级块，对内存中的超级块和磁盘中的超级块进行同步

        int (*sync_fs) (struct super_block *, int);//使文件系统的数据元和磁盘上的文件系统同步

        void (*write_super_lockfs) (struct super_block *);//禁止对文件系统做改变，再更新磁盘上的超级块

        void (*unlockfs) (struct super_block *);//对文件解除锁定

        int (*statfs) (struct super_block *, struct statfs *);//获取文件系统状态

        int (*remount_fs) (struct super_block *, int *, char *);//当指定新的安装选项重新安装文件系统时调用此函数

        void (*clear_inode) (struct inode *);//释放索引节点并清空包含相关数据的所有页面

        void (*umount_begin) (struct super_block *);//中断安装操作，用于网络文件系统(如NFS)

        int (*show_options) (struct seq_file *, struct vfsmount *);
};

    struct inode {
        struct hlist_node i_hash; /* hash list */
        struct list_head i_list; /* list of inodes */
        struct list_head i_dentry; /* list of dentries */
        unsigned long i_ino; /* inode number */
        atomic_t i_count; /* reference counter */
        umode_t i_mode; /* access permissions */
        unsigned int i_nlink; /* number of hard links */
        uid_t i_uid; /* user id of owner */
        gid_t i_gid; /* group id of owner */
        kdev_t i_rdev; /* real device node */
        loff_t i_size; /* file size in bytes */
        struct timespec i_atime; /* last access time */
        struct timespec i_mtime; /* last modify time */
        struct timespec i_ctime; /* last change time */
        unsigned int i_blkbits; /* block size in bits */
        unsigned long i_blksize; /* block size in bytes */
        unsigned long i_version; /* version number */
        unsigned long i_blocks; /* file size in blocks */
        unsigned short i_bytes; /* bytes consumed */
        spinlock_t i_lock; /* spinlock */
        struct rw_semaphore i_alloc_sem; /* nests inside of i_sem */
        struct semaphore i_sem; /* inode semaphore */
        struct inode_operations *i_op; /* inode ops table */
        struct file_operations *i_fop; /* default inode ops */
        struct super_block *i_sb; /* associated superblock */
        struct file_lock *i_flock; /* file lock list */
        struct address_space *i_mapping; /* associated mapping */
        struct address_space i_data; /* mapping for device */
        struct dquot *i_dquot[MAXQUOTAS]; /* disk quotas for inode */
        struct list_head i_devices; /* list of block devices */
        struct pipe_inode_info *i_pipe; /* pipe information */
        struct block_device *i_bdev; /* block device driver */
        unsigned long i_dnotify_mask; /* directory notify mask */
        struct dnotify_struct *i_dnotify; /* dnotify */
        unsigned long i_state; /* state flags */
        unsigned long dirtied_when; /* first dirtying time */
        unsigned int i_flags; /* filesystem flags */
        unsigned char i_sock; /* is this a socket? */
        atomic_t i_writecount; /* count of writers */
        void *i_security; /* security module */
        __u32 i_generation; /* inode version number */
        union {
                void *generic_ip; /* filesystem-specific info */
        } u;
};

struct inode_operations {
        int (*create) (struct inode *, struct dentry *,int);//为dentry对象创建新的索引节点
        struct dentry * (*lookup) (struct inode *, struct dentry *);//在特定目录中寻找索引节点
        int (*link) (struct dentry *, struct inode *, struct dentry *);//被系统调用link()调用，创建硬链接
        int (*unlink) (struct inode *, struct dentry *);//被系统调用unlink()调用，从目录dir中删除由目录项dentry指定的索引节点对象
        int (*symlink) (struct inode *, struct dentry *, const char *);//系统调用symlink()，创建符号链接
        int (*mkdir) (struct inode *, struct dentry *, int);//系统调用mkdir()，创建一个新目录
        int (*rmdir) (struct inode *, struct dentry *);
        int (*mknod) (struct inode *, struct dentry *, int, dev_t);//系统调用mknod()，创建特殊文件
        int (*rename) (struct inode *, struct dentry *,
                       struct inode *, struct dentry *);//移动文件
        int (*readlink) (struct dentry *, char *, int);//系统调用readlink()，拷贝数据到特定的缓冲buffer中
        int (*follow_link) (struct dentry *, struct nameidata *);//从一个符号链接查找它指向的索引节点
        int (*put_link) (struct dentry *, struct nameidata *);
        void (*truncate) (struct inode *);//修改文件大小
        int (*permission) (struct inode *, int);//检查给定的inode所代表的文件是否允许特定的访问模式
        int (*setattr) (struct dentry *, struct iattr *);//被notify_change()调用，修改索引节点后，通知发生了“改变事件”
        int (*getattr) (struct vfsmount *, struct dentry *, struct kstat *);//通知索引节点需要从磁盘中更新时，调用
        int (*setxattr) (struct dentry *, const char *,//给dentry指定的文件设置扩展属性
                         const void *, size_t, int);
        ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);//向value中拷贝给定文件的扩展属性name对应的数值
        ssize_t (*listxattr) (struct dentry *, char *, size_t);//将特定文件的所有属性列表拷贝到一个缓冲列表中。
        int (*removexattr) (struct dentry *, const char *);//从文件中删除指定的属性
}

struct dentry {
        atomic_t d_count; /* usage count */
        unsigned long d_vfs_flags; /* dentry cache flags */
        spinlock_t d_lock; /* per-dentry lock */
        struct inode *d_inode; /* associated inode */
        struct list_head d_lru; /* unused list */
        struct list_head d_child; /* list of dentries within */
        struct list_head d_subdirs; /* subdirectories */
        struct list_head d_alias; /* list of alias inodes */
        unsigned long d_time; /* revalidate time */
        struct dentry_operations *d_op; /* dentry operations table */
        struct super_block *d_sb; /* superblock of file */
        unsigned int d_flags; /* dentry flags */
        int d_mounted; /* is this a mount point? */
        void *d_fsdata; /* filesystem-specific data */
        struct rcu_head d_rcu; /* RCU locking */
        struct dcookie_struct *d_cookie; /* cookie */
        struct dentry *d_parent; /* dentry object of parent */
        struct qstr d_name; /* dentry name */
        struct hlist_node d_hash; /* list of hash table entries */
        struct hlist_head *d_bucket; /* hash bucket */
        unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* short name */
};

    struct dentry_operations {
        int (*d_revalidate) (struct dentry *, int);//判断目录对象是否有效

        int (*d_hash) (struct dentry *, struct qstr *);//为目录项生成散列表

        int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);//比较两个文件名

        int (*d_delete) (struct dentry *);//当目录项对象的d_count值为0时，调用此函数

        void (*d_release) (struct dentry *);//释放目录项对象

        void (*d_iput) (struct dentry *, struct inode *);//当一个目录项丢失相关索引节点时调用

};

    struct file {
        struct list_head f_list; /* list of file objects */
        struct dentry *f_dentry; /* associated dentry object */
        struct vfsmount *f_vfsmnt; /* associated mounted fs */
        struct file_operations *f_op; /* file operations table */
        atomic_t f_count; /* file object's usage count */
        unsigned int f_flags; /* flags specified on open */
        mode_t f_mode; /* file access mode */
        loff_t f_pos; /* file offset (file pointer) */
        struct fown_struct f_owner; /* owner data for signals */
        unsigned int f_uid; /* user's UID */
        unsigned int f_gid; /* user's GID */
        int f_error; /* error code */
        struct file_ra_state f_ra; /* read-ahead state */
        unsigned long f_version; /* version number */
        void *f_security; /* security module */
        void *private_data; /* tty driver hook */
        struct list_head f_ep_links; /* list of eventpoll links */
        spinlock_t f_ep_lock; /* eventpoll lock */
        struct address_space *f_mapping; /* page cache mapping */
};

    struct file_operations {
        struct module *owner;
        loff_t (*llseek) (struct file *, loff_t, int);
        ssize_t (*read) (struct file *, char *, size_t, loff_t *);
        ssize_t (*aio_read) (struct kiocb *, char *, size_t, loff_t);
        ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
        ssize_t (*aio_write) (struct kiocb *, const char *, size_t, loff_t);
        int (*readdir) (struct file *, void *, filldir_t);
        unsigned int (*poll) (struct file *, struct poll_table_struct *);
        int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
        int (*mmap) (struct file *, struct vm_area_struct *);
        int (*open) (struct inode *, struct file *);
        int (*flush) (struct file *);
        int (*release) (struct inode *, struct file *);
        int (*fsync) (struct file *, struct dentry *, int);
        int (*aio_fsync) (struct kiocb *, int);
        int (*fasync) (int, struct file *, int);
        int (*lock) (struct file *, int, struct file_lock *);
        ssize_t (*readv) (struct file *, const struct iovec *,
                          unsigned long, loff_t *);
        ssize_t (*writev) (struct file *, const struct iovec *,
                           unsigned long, loff_t *);
        ssize_t (*sendfile) (struct file *, loff_t *, size_t,
                             read_actor_t, void *);
        ssize_t (*sendpage) (struct file *, struct page *, int,
                             size_t, loff_t *, int);
        unsigned long (*get_unmapped_area) (struct file *, unsigned long,
                                            unsigned long, unsigned long,
                                            unsigned long);
        int (*check_flags) (int flags);
        int (*dir_notify) (struct file *filp, unsigned long arg);
        int (*flock) (struct file *filp, int cmd, struct file_lock *fl);
};

struct file_system_type {
        const char *name; /* filesystem's name */
        struct subsystem subsys; /* sysfs subsystem object */
        int fs_flags; /* filesystem type flags */

        /* the following is used to read the superblock off the disk */
        struct super_block *(*get_sb) (struct file_system_type *, int,
                                            char *, void *);

        /* the following is used to terminate access to the superblock */
        void (*kill_sb) (struct super_block *);

        struct module *owner; /* module owning the filesystem */
        struct file_system_type *next; /* next file_system_type in list */
        struct list_head fs_supers; /* list of superblock objects */
};

struct vfsmount {
        struct list_head mnt_hash; /* hash table list */
        struct vfsmount *mnt_parent; /* parent filesystem */
        struct dentry *mnt_mountpoint; /* dentry of this mount point */
        struct dentry *mnt_root; /* dentry of root of this fs */
        struct super_block *mnt_sb; /* superblock of this filesystem */
        struct list_head mnt_mounts; /* list of children */
        struct list_head mnt_child; /* list of children */
        atomic_t mnt_count; /* usage count */
        int mnt_flags; /* mount flags */
        char *mnt_devname; /* device file name */
        struct list_head mnt_list; /* list of descriptors */
        struct list_head mnt_fslink; /* fs-specific expiry list */
        struct namespace *mnt_namespace /* associated namespace */
};