inode结构体

参考：Linux字符设备中的两个重要结构体（file、inode）

inode分为内存中的inode和文件系统中的inode，为了避免混淆，我们称前者为VFS inode， 而后者以EXT2为代表，我们称为Ext2 inod。这里说明的是VFS inode。

重要成员：

1. struct cdev *i_cdev;

若是字符设备，为其对应的cdev结构体指针。

2. struct block_device *i_bdev;

若是块设备，为其对应的block_device结构体指针

3. dev_t i_rdev;

若是设备文件，此成员记录设备的设备号

 struct inode {
     /* RCU path lookup touches following: */
     umode_t            i_mode;
     uid_t            i_uid;
     gid_t            i_gid;
     const struct inode_operations    *i_op;
     struct super_block    *i_sb;

     spinlock_t        i_lock;    /* i_blocks, i_bytes, maybe i_size */
     unsigned int        i_flags;
     unsigned long        i_state;
 #ifdef CONFIG_SECURITY
     void            *i_security;
 #endif
     struct mutex        i_mutex;

     unsigned long        dirtied_when;    /* jiffies of first dirtying */

     struct hlist_node    i_hash;
     struct list_head    i_wb_list;    /* backing dev IO list */
     struct list_head    i_lru;        /* inode LRU list */
     struct list_head    i_sb_list;
     union {
         struct list_head    i_dentry;
         struct rcu_head        i_rcu;
     };
     unsigned long        i_ino;
     atomic_t        i_count;
     unsigned int        i_nlink;
     dev_t            i_rdev;
     unsigned int        i_blkbits;
     u64            i_version;
     loff_t            i_size;
 #ifdef __NEED_I_SIZE_ORDERED
     seqcount_t        i_size_seqcount;
 #endif
     struct timespec        i_atime;
     struct timespec        i_mtime;
     struct timespec        i_ctime;
     blkcnt_t        i_blocks;
     unsigned short          i_bytes;
     struct rw_semaphore    i_alloc_sem;
     const struct file_operations    *i_fop;    /* former ->i_op->default_file_ops */
     struct file_lock    *i_flock;
     struct address_space    *i_mapping;
     struct address_space    i_data;
 #ifdef CONFIG_QUOTA
     struct dquot        *i_dquot[MAXQUOTAS];
 #endif
     struct list_head    i_devices;
     union {
         struct pipe_inode_info    *i_pipe;
         struct block_device    *i_bdev;
         struct cdev        *i_cdev;
     };

     __u32            i_generation;

 #ifdef CONFIG_FSNOTIFY
     __u32            i_fsnotify_mask; /* all events this inode cares about */
     struct hlist_head    i_fsnotify_marks;
 #endif

 #ifdef CONFIG_IMA
     atomic_t        i_readcount; /* struct files open RO */
 #endif
     atomic_t        i_writecount;
 #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 */
 };