Linux内核文件系统6

2021SC@SDUSC

继续分析ext4.h文件

/*超级块的结构*/
struct ext4_super_block {
/*00*/	__le32	s_inodes_count;		/* Inodes count */
	__le32	s_blocks_count_lo;	/* Blocks count */
	__le32	s_r_blocks_count_lo;	/* 保留块数*/
	__le32	s_free_blocks_count_lo;	/* 空闲块数*/
/*10*/	__le32	s_free_inodes_count;	/* Free inodes count */
	__le32	s_first_data_block;	/*第一个数据块*/
	__le32	s_log_block_size;	/*块大小*/
	__le32	s_log_cluster_size;	/*分配集群大小*/
/*20*/	__le32	s_blocks_per_group;	/* #每组的块数*/
	__le32	s_clusters_per_group;	/* #每组的集群数*/
	__le32	s_inodes_per_group;	/* # Inodes per group */
	__le32	s_mtime;		/*挂载时间*/
/*30*/	__le32	s_wtime;		/*写入时间*/
	__le16	s_mnt_count;		/*挂载次数*/
	__le16	s_max_mnt_count;	/*最大装载计数*/
	__le16	s_magic;		/*神奇的签名*/
	__le16	s_state;		/*文件系统状态*/
	__le16	s_errors;		/*检测错误时的行为*/
	__le16	s_minor_rev_level;	/*轻微的修订版本*/
/*40*/	__le32	s_lastcheck;		/*最后检查时间*/
	__le32	s_checkinterval;	/* max. time between checks */
	__le32	s_creator_os;		/* OS */
	__le32	s_rev_level;		/* Revision level */
/*50*/	__le16	s_def_resuid;		/*预留块的默认uid*/
	__le16	s_def_resgid;		/*保留块的默认gid*/

	/*这些字段仅适用于EXT4_DYNAMIC_REV超级块。
	需要注意兼容的特性集和不兼容的特性集之间的区别，如果不兼容的特	性集中有一个位集是内核不知道的，它应该拒绝挂载文件系统。
	e2fsck的要求更严格;如果它不知道兼容或不兼容特性集中的某个特性，	它必须中止，并且不尝试去干涉它不理解的事情……
	*/
	__le32	s_first_ino;		/* First non-reserved inode */
	__le16  s_inode_size;		/* size of inode structure */
	__le16	s_block_group_nr;	/*该超级块的Block group #*/
	__le32	s_feature_compat;	/*兼容的特性集*/
/*60*/	__le32	s_feature_incompat;	/*不兼容的特性集*/
	__le32	s_feature_ro_compat;	/*只读兼容特性集*/
/*68*/	__u8	s_uuid[16];		/* 128-bit uuid for volume */
/*78*/	char	s_volume_name[16];	/* volume name */
/*88*/	char	s_last_mounted[64] __nonstring;/*最后挂载的目录*/
/*C8*/	__le32	s_algorithm_usage_bitmap; /* For compression */
	/*性能提示。目录预分配应该只在	EXT4_FEATURE_COMPAT_DIR_PREALLOC标志开启的情况下才会发生。
	*/
	__u8	s_prealloc_blocks;	/* Nr of blocks to try to preallocate*/
	__u8	s_prealloc_dir_blocks;	/* Nr to preallocate for dirs */
	__le16	s_reserved_gdt_blocks;	/* Per group desc for online growth */

	/*
	如果EXT4_FEATURE_COMPAT_HAS_JOURNAL设置，那么日志支持有效。	*/
/*D0*/	__u8	s_journal_uuid[16];	/*日志超级块的uuid*/
/*E0*/	__le32	s_journal_inum;		/*日志文件的inode数 */
	__le32	s_journal_dev;		/* device number of journal file */
	__le32	s_last_orphan;		/*要删除的inode列表的开始*/
	__le32	s_hash_seed[4];		/* HTREE hash seed */
	__u8	s_def_hash_version;	/*默认使用的哈希版本*/
	__u8	s_jnl_backup_type;
	__le16  s_desc_size;		/* size of group descriptor */
/*100*/	__le32	s_default_mount_opts;
	__le32	s_first_meta_bg;	/*第一个元块的块组*/
	__le32	s_mkfs_time;		/*创建文件系统的时间*/
	__le32	s_jnl_blocks[17];	/* Backup of the journal inode */
	/* 64bit support valid if EXT4_FEATURE_COMPAT_64BIT */
/*150*/	__le32	s_blocks_count_hi;	/* Blocks count */
	__le32	s_r_blocks_count_hi;	/* Reserved blocks count */
	__le32	s_free_blocks_count_hi;	/* Free blocks count */
	__le16	s_min_extra_isize;	/*所有索引节点都至少有#字节*/
	__le16	s_want_extra_isize; 	/*新的索引节点应该保留# bytes*/
	__le32	s_flags;		/* Miscellaneous flags */
	__le16  s_raid_stride;		/* RAID stride */
	__le16  s_mmp_update_interval;  /*等待MMP检查#秒数*/
	__le64  s_mmp_block;            /*多挂载保护块*/
	__le32  s_raid_stripe_width;    /*所有数据磁盘上的块(N*stride)*/
	__u8	s_log_groups_per_flex;  /* FLEX_BG group size */
	__u8	s_checksum_type;	/*使用元数据校验和算法*/
	__u8	s_encryption_level;	/*加密的版本级别*/
	__u8	s_reserved_pad;		/*填充到下一个32位*/
	__le64	s_kbytes_written;	/*写入生命周期的千字节数为Nr*/
	__le32	s_snapshot_inum;	/*活动快照的Inode个数*/
	__le32	s_snapshot_id;		/*活动快照的顺序ID*/
	__le64	s_snapshot_r_blocks_count; /*为活动快照未来使用的保留块*/
	__le32	s_snapshot_list;	/*磁盘快照列表头部的Inode号*/
#define EXT4_S_ERR_START offsetof(struct ext4_super_block, s_error_count)
	__le32	s_error_count;		/* number of fs errors */
	__le32	s_first_error_time;	/* first time an error happened */
	__le32	s_first_error_ino;	/*第一个错误涉及的Inode*/
	__le64	s_first_error_block;	/*第一个错误涉及的块*/
	__u8	s_first_error_func[32] __nonstring;	/*第一个函数发生错误的地方*/
	__le32	s_first_error_line;	/* line number where error happened */
	__le32	s_last_error_time;	/* most recent time of an error */
	__le32	s_last_error_ino;	/* inode involved in last error */
	__le32	s_last_error_line;	/* line number where error happened */
	__le64	s_last_error_block;	/* block involved of last error */
	__u8	s_last_error_func[32] __nonstring;	/* function where the error happened */
#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_mount_opts)
	__u8	s_mount_opts[64];
	__le32	s_usr_quota_inum;	/*用于跟踪用户配额的Inode*/
	__le32	s_grp_quota_inum;	/*用于跟踪组配额的Inode*/
	__le32	s_overhead_clusters;	/*文件系统中的开销块/集群*/
	__le32	s_backup_bgs[2];	/*使用sparse_super2 SBs的组*/
	__u8	s_encrypt_algos[4];	/*使用中的加密算法*/
	__u8	s_encrypt_pw_salt[16];	/*用于string2key算法的Salt*/
	__le32	s_lpf_ino;		/* Location of the lost+found inode */
	__le32	s_prj_quota_inum;	/*用于追踪项目配额的Inode*/
	__le32	s_checksum_seed;	/*如果csum_seed设置了，用于Crc32c (uuid)*/
	__u8	s_wtime_hi;
	__u8	s_mtime_hi;
	__u8	s_mkfs_time_hi;
	__u8	s_lastcheck_hi;
	__u8	s_first_error_time_hi;
	__u8	s_last_error_time_hi;
	__u8	s_first_error_errcode;
	__u8    s_last_error_errcode;
	__le16  s_encoding;		/*文件名字符集编码*/
	__le16  s_encoding_flags;	/*文件名字符集编码标志*/
	__le32  s_orphan_file_inum;	/* Inode for tracking orphan inodes */
	__le32	s_reserved[94];		/*填充到块的末尾*/
	__le32	s_checksum;		/* crc32c(superblock) */
};

#define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)

#ifdef __KERNEL__

#ifdef CONFIG_FS_ENCRYPTION
#define DUMMY_ENCRYPTION_ENABLED(sbi) ((sbi)->s_dummy_enc_policy.policy != NULL)
#else
#define DUMMY_ENCRYPTION_ENABLED(sbi) (0)
#endif

/*我们支持的配额类型数量*/
#define EXT4_MAXQUOTAS 3

#define EXT4_ENC_UTF8_12_1	1

/*ext4日志触发器的类型*/
enum ext4_journal_trigger_type {
	EXT4_JTR_ORPHAN_FILE,
	EXT4_JTR_NONE	/*这必须是索引工作的最后一个条目!*/
};

#define EXT4_JOURNAL_TRIGGER_COUNT EXT4_JTR_NONE

struct ext4_journal_trigger {
	struct jbd2_buffer_trigger_type tr_triggers;
	struct super_block *sb;
};

static inline struct ext4_journal_trigger *EXT4_TRIGGER(
				struct jbd2_buffer_trigger_type *trigger)
{
	return container_of(trigger, struct ext4_journal_trigger, tr_triggers);
}

#define EXT4_ORPHAN_BLOCK_MAGIC 0x0b10ca04

/*在orphan块的尾部的结构*/
struct ext4_orphan_block_tail {
	__le32 ob_magic;
	__le32 ob_checksum;
};

static inline int ext4_inodes_per_orphan_block(struct super_block *sb)
{
	return (sb->s_blocksize - sizeof(struct ext4_orphan_block_tail)) /
			sizeof(u32);
}

struct ext4_orphan_block {
	atomic_t ob_free_entries;	/*块中自由orphan条目的数量*/
	struct buffer_head *ob_bh;	/*orphan block 的缓存*/
};

/*orphan文件的信息。*/
struct ext4_orphan_info {
	int of_blocks;			/*一个文件中orphan块的数量*/
	__u32 of_csum_seed;		/*orphan文件的校验和种子*/
	struct ext4_orphan_block *of_binfo;	/*包含orphan文件块信息的数组*/
};

/*内存中的第四代扩展文件系统超级块数据*/
struct ext4_sb_info {
	unsigned long s_desc_size;	/*以字节为单位组描述符的大小*/
	unsigned long s_inodes_per_block;/* Number of inodes per block */
	unsigned long s_blocks_per_group;/* Number of blocks in a group */
	unsigned long s_clusters_per_group; /* Number of clusters in a group */
	unsigned long s_inodes_per_group;/* Number of inodes in a group */
	unsigned long s_itb_per_group;	/* Number of inode table blocks per group */
	unsigned long s_gdb_count;	/* Number of group descriptor blocks */
	unsigned long s_desc_per_block;	/* Number of group descriptors per block */
	ext4_group_t s_groups_count;	/* Number of groups in the fs */
	ext4_group_t s_blockfile_groups;/*可用于非扩展区文件的组*/
	unsigned long s_overhead;  /*fs开销集群的#*/
	unsigned int s_cluster_ratio;	/* Number of blocks per cluster */
	unsigned int s_cluster_bits;	/* log2 of s_cluster_ratio */
	loff_t s_bitmap_maxbytes;	/* max bytes for bitmap files */
	struct buffer_head * s_sbh;	/*包含超级块的缓冲区*/
	struct ext4_super_block *s_es;	/*指向缓冲区中的超级块的指针*/
	struct buffer_head * __rcu *s_group_desc;
	unsigned int s_mount_opt;
	unsigned int s_mount_opt2;
	unsigned long s_mount_flags;
	unsigned int s_def_mount_opt;
	ext4_fsblk_t s_sb_block;
	atomic64_t s_resv_clusters;
	kuid_t s_resuid;
	kgid_t s_resgid;
	unsigned short s_mount_state;
	unsigned short s_pad;
	int s_addr_per_block_bits;
	int s_desc_per_block_bits;
	int s_inode_size;
	int s_first_ino;
	unsigned int s_inode_readahead_blks;
	unsigned int s_inode_goal;
	u32 s_hash_seed[4];
	int s_def_hash_version;
	int s_hash_unsigned;	/*如果哈希值为无符号则为3，否则为0*/
	struct percpu_counter s_freeclusters_counter;
	struct percpu_counter s_freeinodes_counter;
	struct percpu_counter s_dirs_counter;
	struct percpu_counter s_dirtyclusters_counter;
	struct percpu_counter s_sra_exceeded_retry_limit;
	struct blockgroup_lock *s_blockgroup_lock;
	struct proc_dir_entry *s_proc;
	struct kobject s_kobj;
	struct completion s_kobj_unregister;
	struct super_block *s_sb;
	struct buffer_head *s_mmp_bh;

	/*日志记录*/
	struct journal_s *s_journal;
	unsigned long s_ext4_flags;		/* Ext4超级块标志*/
	struct mutex s_orphan_lock;	/*保护磁盘列表更改*/
	struct list_head s_orphan;	/*磁盘列表中孤立的索引节点的列表*/
	struct ext4_orphan_info s_orphan_info;
	unsigned long s_commit_interval;
	u32 s_max_batch_time;
	u32 s_min_batch_time;
	struct block_device *s_journal_bdev;
#ifdef CONFIG_QUOTA
	/*具有日志配额的配额文件的名称*/
	char __rcu *s_qf_names[EXT4_MAXQUOTAS];
	int s_jquota_fmt;			/*要使用的配额格式*/
#endif
	unsigned int s_want_extra_isize; /*新的索引节点应该保留# bytes*/
	struct ext4_system_blocks __rcu *s_system_blks;

#ifdef EXTENTS_STATS
	/*ext4区段数据*/
	unsigned long s_ext_min;
	unsigned long s_ext_max;
	unsigned long s_depth_max;
	spinlock_t s_ext_stats_lock;
	unsigned long s_ext_blocks;
	unsigned long s_ext_extents;
#endif

	/* for buddy allocator */
	struct ext4_group_info ** __rcu *s_group_info;
	struct inode *s_buddy_cache;
	spinlock_t s_md_lock;
	unsigned short *s_mb_offsets;
	unsigned int *s_mb_maxs;
	unsigned int s_group_info_size;
	unsigned int s_mb_free_pending;
	struct list_head s_freed_data_list;	/*完成提交后要释放的块列表*/
	struct list_head s_discard_list;
	struct work_struct s_discard_work;
	atomic_t s_retry_alloc_pending;
	struct rb_root s_mb_avg_fragment_size_root;
	rwlock_t s_mb_rb_lock;
	struct list_head *s_mb_largest_free_orders;
	rwlock_t *s_mb_largest_free_orders_locks;

	/*可调参数*/
	unsigned long s_stripe;
	unsigned int s_mb_max_linear_groups;
	unsigned int s_mb_stream_request;
	unsigned int s_mb_max_to_scan;
	unsigned int s_mb_min_to_scan;
	unsigned int s_mb_stats;
	unsigned int s_mb_order2_reqs;
	unsigned int s_mb_group_prealloc;
	unsigned int s_mb_max_inode_prealloc;
	unsigned int s_max_dir_size_kb;
	/* where last allocation was done - for stream allocation */
	unsigned long s_mb_last_group;
	unsigned long s_mb_last_start;
	unsigned int s_mb_prefetch;
	unsigned int s_mb_prefetch_limit;

	/*buddy分配程序的统计信息*/
	atomic_t s_bal_reqs;	/*长度大于1的请求数*/
	atomic_t s_bal_success;	/*我们找到了足够长的块*/
	atomic_t s_bal_allocated;	/* in blocks */
	atomic_t s_bal_ex_scanned;	/*总区段扫描*/
	atomic_t s_bal_groups_scanned;	/* number of groups scanned */
	atomic_t s_bal_goals;	/*目标命中*/
	atomic_t s_bal_breaks;	/* too long searches */
	atomic_t s_bal_2orders;	/* 2^order hits */
	atomic_t s_bal_cr0_bad_suggestions;
	atomic_t s_bal_cr1_bad_suggestions;
	atomic64_t s_bal_cX_groups_considered[4];
	atomic64_t s_bal_cX_hits[4];
	atomic64_t s_bal_cX_failed[4];		/*cX循环没有找到块*/
	atomic_t s_mb_buddies_generated;	/*生成的伙伴数*/
	atomic64_t s_mb_generation_time;
	atomic_t s_mb_lost_chunks;
	atomic_t s_mb_preallocated;
	atomic_t s_mb_discarded;
	atomic_t s_lock_busy;

	/*存储位置分组*/
	struct ext4_locality_group __percpu *s_locality_groups;

	/*写入统计*/
	unsigned long s_sectors_written_start;
	u64 s_kbytes_written;

	/*零输出块的大小*/
	unsigned int s_extent_max_zeroout_kb;

	unsigned int s_log_groups_per_flex;
	struct flex_groups * __rcu *s_flex_groups;
	ext4_group_t s_flex_groups_allocated;

	/*用于保留区段转换的工作队列(缓冲io)*/
	struct workqueue_struct *rsv_conversion_wq;

	/*定时错误统计打印*/
	struct timer_list s_err_report;

	/*延迟inode表初始化信息*/
	struct ext4_li_request *s_li_request;
	/*等待乘数来惰性地初始化线程*/
	unsigned int s_li_wait_mult;

	/*多个挂载保护的内核线程*/
	struct task_struct *s_mmp_tsk;

	/*记录FITRIM被调用时的最后minlen。*/
	atomic_t s_last_trim_minblks;

	/*通过cryptoapi引用校验和算法驱动程序*/
	struct crypto_shash *s_chksum_driver;

	/*预先计算的FS UUID校验和用于其他校验和的种子*/
	__u32 s_csum_seed;

	/*从区段状态树中回收区段*/
	struct shrinker s_es_shrinker;
	struct list_head s_es_list;	/* List of inodes with reclaimable extents */
	long s_es_nr_inode;
	struct ext4_es_stats s_es_stats;
	struct mb_cache *s_ea_block_cache;
	struct mb_cache *s_ea_inode_cache;
	spinlock_t s_es_lock ____cacheline_aligned_in_smp;

	/*日志触发器用于校验和计算*/
	struct ext4_journal_trigger s_journal_triggers[EXT4_JOURNAL_TRIGGER_COUNT];

	/*Ratelimit ext4的消息。*/
	struct ratelimit_state s_err_ratelimit_state;
	struct ratelimit_state s_warning_ratelimit_state;
	struct ratelimit_state s_msg_ratelimit_state;
	atomic_t s_warning_count;
	atomic_t s_msg_count;

	/*'-o test_dummy_encryption'的加密策略*/
	struct fscrypt_dummy_policy s_dummy_enc_policy;

	/*
	设置在写页面操作和更改任何inode的JOURNAL_DATA或EXTENTS标	志之间的障碍。
	*/
	struct percpu_rw_semaphore s_writepages_rwsem;
	struct dax_device *s_daxdev;
#ifdef CONFIG_EXT4_DEBUG
	unsigned long s_simulate_fail;
#endif
	/*记录后端块设备的errseq*/
	errseq_t s_bdev_wb_err;
	spinlock_t s_bdev_wb_lock;

	/*关于此挂载期间发生的错误的信息*/
	spinlock_t s_error_lock;
	int s_add_error_count;
	int s_first_error_code;
	__u32 s_first_error_line;
	__u32 s_first_error_ino;
	__u64 s_first_error_block;
	const char *s_first_error_func;
	time64_t s_first_error_time;
	int s_last_error_code;
	__u32 s_last_error_line;
	__u32 s_last_error_ino;
	__u64 s_last_error_block;
	const char *s_last_error_func;
	time64_t s_last_error_time;
	/*
	 	如果我们无法在磁盘上的超级块中更新错误信息，我们将此工作加入等	待队列，直到它执行结束。
	 */
	struct work_struct s_error_work;

	/* Ext4快速提交的数据*/
	atomic_t s_fc_subtid;
	atomic_t s_fc_ineligible_updates;
	/*
	 提交开始后，主队列被锁定，进一步的更新被添加到暂存队列中。
	 */
#define FC_Q_MAIN	0
#define FC_Q_STAGING	1
	struct list_head s_fc_q[2];	/*暂存的索引节点用于快速提交，其中包含数据更改。*/
	struct list_head s_fc_dentry_q[2];	/*目录项更新*/
	unsigned int s_fc_bytes;
	/*
	 *主要的快速提交锁。这个锁保护对以下字段的访问:
	 * ei - > i_fc_list, s_fc_dentry_q、s_fc_q s_fc_bytes s_fc_bh。
	 */
	spinlock_t s_fc_lock;
	struct buffer_head *s_fc_bh;
	struct ext4_fc_stats s_fc_stats;
	u64 s_fc_avg_commit_time;
#ifdef CONFIG_EXT4_DEBUG
	int s_fc_debug_max_replay;
#endif
	struct ext4_fc_replay_state s_fc_replay_state;
};
/*返回超级块信息*/
static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}
/*返回Inode信息*/
static inline struct ext4_inode_info *EXT4_I(struct inode *inode)
{
	return container_of(inode, struct ext4_inode_info, vfs_inode);
}

static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
{
	return ino == EXT4_ROOT_INO ||
		(ino >= EXT4_FIRST_INO(sb) &&
		 ino <= le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count));
}

/*
 * 返回数据: sbi->field[index]
 * 用于从下列需要的sbi字段中访问数组元素
 * Rcu保护，避免由于重赋值而对无效指针进行解引用
 * - s_group_desc
 * - s_group_info
 * - s_flex_group
 */
#define sbi_array_rcu_deref(sbi, field, index)				   \
({									   \
	typeof(*((sbi)->field)) _v;					   \
	rcu_read_lock();						   \
	_v = ((typeof(_v)*)rcu_dereference((sbi)->field))[index];	   \
	rcu_read_unlock();						   \
	_v;								   \
})

/*
 *运行时mount标志
 */
enum {
	EXT4_MF_MNTDIR_SAMPLED,
	EXT4_MF_FS_ABORTED,	/* Fatal error detected */
	EXT4_MF_FC_INELIGIBLE,	/* Fast commit ineligible */
	EXT4_MF_FC_COMMITTING	/*正在快速提交的文件系统。*/
};

static inline void ext4_set_mount_flag(struct super_block *sb, int bit)
{
	set_bit(bit, &EXT4_SB(sb)->s_mount_flags);
}

static inline void ext4_clear_mount_flag(struct super_block *sb, int bit)
{
	clear_bit(bit, &EXT4_SB(sb)->s_mount_flags);
}

static inline int ext4_test_mount_flag(struct super_block *sb, int bit)
{
	return test_bit(bit, &EXT4_SB(sb)->s_mount_flags);
}


/*
 * Simulate_fail代码
 */
#define EXT4_SIM_BBITMAP_EIO	1
#define EXT4_SIM_BBITMAP_CRC	2
#define EXT4_SIM_IBITMAP_EIO	3
#define EXT4_SIM_IBITMAP_CRC	4
#define EXT4_SIM_INODE_EIO	5
#define EXT4_SIM_INODE_CRC	6
#define EXT4_SIM_DIRBLOCK_EIO	7
#define EXT4_SIM_DIRBLOCK_CRC	8

static inline bool ext4_simulate_fail(struct super_block *sb,
				     unsigned long code)
{
#ifdef CONFIG_EXT4_DEBUG
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	if (unlikely(sbi->s_simulate_fail == code)) {
		sbi->s_simulate_fail = 0;
		return true;
	}
#endif
	return false;
}

static inline void ext4_simulate_fail_bh(struct super_block *sb,
					 struct buffer_head *bh,
					 unsigned long code)
{
	if (!IS_ERR(bh) && ext4_simulate_fail(sb, code))
		clear_buffer_uptodate(bh);
}

/*
 * 错误码s_{第一个，最后一个}_error_errno修改翻译结果
 *Linux errno数字是特定于体系结构的，因此我们需要将它们转换为与体系结*构无关的东西。我们没有为所有的errno定义代码;只是那些最有可能是*ext4_error()调用的原因。
 * 
 */
#define EXT4_ERR_UNKNOWN	 1
#define EXT4_ERR_EIO		 2
#define EXT4_ERR_ENOMEM		 3
#define EXT4_ERR_EFSBADCRC	 4
#define EXT4_ERR_EFSCORRUPTED	 5
#define EXT4_ERR_ENOSPC		 6
#define EXT4_ERR_ENOKEY		 7
#define EXT4_ERR_EROFS		 8
#define EXT4_ERR_EFBIG		 9
#define EXT4_ERR_EEXIST		10
#define EXT4_ERR_ERANGE		11
#define EXT4_ERR_EOVERFLOW	12
#define EXT4_ERR_EBUSY		13
#define EXT4_ERR_ENOTDIR	14
#define EXT4_ERR_ENOTEMPTY	15
#define EXT4_ERR_ESHUTDOWN	16
#define EXT4_ERR_EFAULT		17

/* Inode动态状态标志*/
enum {
	EXT4_STATE_JDATA,		/* journaled data exists */
	EXT4_STATE_NEW,			/* inode is newly created */
	EXT4_STATE_