Linux虚拟文件系统(VFS)学习

struct inode { struct hlist_node i_hash; //用于散列链表 struct list_head i_list; /* backing dev IO list */ struct list_head i_sb_list; struct list_head i_dentry; //援用索引节点的目录项对象链表头 unsigned long i_ino; //索引节点号 atomic_t i_count; //援用计数器 unsigned int i_nlink; //硬链接数目 uid_t i_uid; //所有者标识符 gid_t i_gid; //组标识符 dev_t i_rdev; //实装备标识符 u64 i_version; //版本号(每次使用后递增) loff_t i_size; //文件的字节数 #ifdef __NEED_I_SIZE_ORDERED seqcount_t i_size_seqcount; #endif struct timespec i_atime; //上次访问文件的时间 struct timespec i_mtime; //上次写文件的时间 struct timespec i_ctime; //上次修改索引节点的时间 blkcnt_t i_blocks; //文件的块数 unsigned int i_blkbits; //块的位数 unsigned short i_bytes;//块的字节数 umode_t i_mode; //文件的类型和访问权限 spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */ struct mutex i_mutex; struct rw_semaphore i_alloc_sem; //在直接I/O文件操作中避免出现竞争条件的读写信号量 const struct inode_operations *i_op; //索引节点的操作 const struct file_operations *i_fop; /*缺省文件操作former ->i_op->default_file_ops */ struct super_block *i_sb; //指向超级块的指针 struct file_lock *i_flock; struct address_space *i_mapping; //指向address_space对象的指针 struct address_space i_data; //文件的address_space对象 #ifdef CONFIG_QUOTA struct dquot *i_dquot[MAXQUOTAS]; //索引节点磁盘限额 #endif struct list_head i_devices; //用于具体的字符或块装备索引节点链表 union { struct pipe_inode_info *i_pipe; //如果文件是个管道则使用它 struct block_device *i_bdev; //指向块装备驱程序的指针 struct cdev *i_cdev; //指向字符装备驱动程序的指针 }; __u32 i_generation; //索引节点的版本号 #ifdef CONFIG_FSNOTIFY __u32 i_fsnotify_mask; /* all events this inode cares about */ struct hlist_head i_fsnotify_mark_entries; /* fsnotify mark entries */ #endif #ifdef CONFIG_INOTIFY struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list */ #endif unsigned long i_state; //索引节点状态标志 unsigned long dirtied_when; /* jiffies of first dirtying */ unsigned int i_flags; //文件系统安装标志 atomic_t i_writecount; #ifdef CONFIG_SECURITY void *i_security; #endif #ifdef CONFIG_FS_POSIX_ACL struct posix_acl *i_acl; struct posix_acl *i_default_acl; #endif void *i_private; /* fs or device private pointer */ };

struct file { /* * fu_list becomes invalid after file_free is called and queued via * fu_rcuhead for RCU freeing */ union { struct list_head fu_list; struct rcu_head fu_rcuhead; } f_u; struct path f_path; #define f_dentry f_path.dentry //与文件相干的目录项对象 #define f_vfsmnt f_path.mnt //含有该文件的已安装文件系统 const struct file_operations *f_op; //文件操作表指针 spinlock_t f_lock; /* f_ep_links, f_flags, no IRQ */ atomic_long_t f_count; //文件对象的援用计数器 unsigned int f_flags; //当打开文件时所指定的标志 fmode_t f_mode; //进程访问模式 loff_t f_pos; //当前的文件偏移量 struct fown_struct f_owner; //通过信号进行I/O事件通知的数据 const struct cred *f_cred; struct file_ra_state f_ra; //文件预读状态 u64 f_version; //版本号，每次使用后自动递增 #ifdef CONFIG_SECURITY void *f_security; #endif /* needed for tty driver, and maybe others */ void *private_data;//指向特定文件系统或装备驱动程序所需要数据的指针 #ifdef CONFIG_EPOLL /* Used by fs/eventpoll.c to link all the hooks to this file */ struct list_head f_ep_links;//文件的事件轮询等待着链表头 #endif /* #ifdef CONFIG_EPOLL */ struct address_space *f_mapping;//指向文件地址空间对象的指针 #ifdef CONFIG_DEBUG_WRITECOUNT unsigned long f_mnt_write_state; #endif };

void __init files_init(unsigned long mempages) { int n; filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); /* * One file with associated inode and dcache is very roughly 1K. * Per default don't use more than 10% of our memory for files. */ n = (mempages * (PAGE_SIZE / 1024)) / 10; files_stat.max_files = n; if (files_stat.max_files < NR_FILE) files_stat.max_files = NR_FILE; files_defer_init(); percpu_counter_init(&nr_files, 0); }

struct dentry { atomic_t d_count; //目录项对象援用计数 unsigned int d_flags; /* 目录项高速缓存标志protected by d_lock */ spinlock_t d_lock; /* per dentry lock */ int d_mounted; //对目录而言，用于记录安装该目录项的文件系统计数器 struct inode *d_inode; /* 与文件名关联的索引节点Where the name belongs to - NULL is * negative */ /* * The next three fields are touched by __d_lookup. Place them here * so they all fit in a cache line. */ struct hlist_node d_hash; /* lookup hash list */ struct dentry *d_parent; /* 父目录的目录项对象parent directory */ struct qstr d_name; //文件名 struct list_head d_lru; /* LRU list */ /* * d_child and d_rcu can share memory */ union { struct list_head d_child; /* child of parent list */ struct rcu_head d_rcu; } d_u; struct list_head d_subdirs; /* our children */ struct list_head d_alias; /* inode alias list */ unsigned long d_time; /* used by d_revalidate */ const struct dentry_operations *d_op;//目录项方法 struct super_block *d_sb; /* 文件的超级块对象The root of the dentry tree */ void *d_fsdata; /* 依赖于文件系统的数据fs-specific data */ unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ };

struct fs_struct { int users; rwlock_t lock; int umask; //当打开文件设置文件权限是所用的位掩码 int in_exec; struct path root, pwd; /* 根目录的目录项，根目录所安装的文件系统对象 当前工作的目录项，当前工作目录所安装的文件系统对象*/ };

struct fdtable { unsigned int max_fds; //文件对象确当前最大数目 struct file ** fd; /* current fd array */ fd_set *close_on_exec; fd_set *open_fds; struct rcu_head rcu; struct fdtable *next; }; /* * Open file table structure */ struct files_struct { /* * read mostly part */ atomic_t count; //同享进程的数目 struct fdtable *fdt; // struct fdtable fdtab; /* * written part on a separate cache line in SMP */ spinlock_t file_lock ____cacheline_aligned_in_smp; int next_fd; struct embedded_fd_set close_on_exec_init; struct embedded_fd_set open_fds_init; struct file * fd_array[NR_OPEN_DEFAULT];//文件对象指针的初始化数组 };

struct file_system_type { const char *name; //文件系统名 int fs_flags; //文件系统标志 int (*get_sb) (struct file_system_type *, int, const char *, void *, struct vfsmount *); //读取超级块的方法 void (*kill_sb) (struct super_block *); //删除超级块的方法 struct module *owner; //指向实现文件系统的模块的指针 struct file_system_type * next;//指向文件系统链表中下1个元素的指针 struct list_head fs_supers; //具有相同文件系统类型的超级块对象链表头 struct lock_class_key s_lock_key; struct lock_class_key s_umount_key; struct lock_class_key i_lock_key; struct lock_class_key i_mutex_key; struct lock_class_key i_mutex_dir_key; struct lock_class_key i_alloc_sem_key; };

static struct file_system_type sock_fs_type = { .name = "sockfs", .get_sb = sockfs_get_sb, .kill_sb = kill_anon_super, }; static int __init sock_init(void) { /* * Initialize sock SLAB cache. */ sk_init(); /* * Initialize skbuff SLAB cache */ skb_init(); /* * Initialize the protocols module. */ init_inodecache(); /* 注册sockfs文件系统 */ register_filesystem(&sock_fs_type); sock_mnt = kern_mount(&sock_fs_type); /* The real protocol initialization is performed in later initcalls. */ #ifdef CONFIG_NETFILTER netfilter_init(); #endif return 0; }